10 Best Quercetin Supplements of 2021: Benefits, Dosage and Side Effects

Quercetin is a type of flavonoid present in many fruits, vegetables, and grains. It’s one of the most abundant antioxidants in the diet and plays an important role in helping your body combat free radical damage, which is linked to chronic diseases. In addition, its antioxidant properties may help reduce inflammation, allergy symptoms, and blood pressure.

Some doctors are advocating its use against SARS-CoV-2 (COVID-19), in combination with vitamin C, noting that Quercetin and Vitamin C have synergistic effects.



There are many quercetin supplement brands available out there. Which one should you buy? Why do we provide so many options below? Many of the brands do go out of stock on Amazon (this article needs to be updated from time to time). You may also have your own set of purchasing criteria and it's likely to be different for different individuals. For example, you might have a preference for liquid form or powder form or capsule form instead of tablet.

Check out below the best quercetin supplements available online. Where to buy quercetin supplements? Order via the links below and it will be delivered to your designated address by Amazon. 

Best Quercetin Supplements 2021

1. Now Foods Quercetin with Bromelain (Now Quercetin with Bromelain Amazon)


$30 - $35 > Check Price (available)

A two-pack of top notch bromelain-enhanced quercetin from a giant in the health supplement industry. Reliable quality from a trustworthy brand.

Each capsule contains 400 mg of quercetin and 82.5 mg of bromelain. Do take note that their suggested usage is 2 capsules twice daily. Meaning the total daily dosage of quercetin will be 1,600 mg daily.

Daily value (DV) for quercetin not established.

Now Foods Quercetin supplements contain Bromelain, as some evidence suggests they boost absorption.

For prevention of COVID-19, the FLCCC recommends 250 mg daily for prevention and the Zelenko protocol recommends 500 mg daily for prevention. If you wish to stick to the dosage which is within the range of the FLCCC - Zelenko protocols; that would be 250 mg to 500 mg daily i.e. 1 capsule of Now Foods Quercetin per day.

BestReviews.com: Not suitable for those with pineapple allergies.

Amazon Best Sellers: #1 Best Seller in Bromelain Nutritional Supplements. 4.7 out of 5 overall rating with more than 5,000 customer reviews.

Our Take: If you are looking for best value and are taking it on a long term basis, this would be your choice.

2. Thorne Research Quercenase  


Quercenase is a combination of quercetin phytosome and bromelain. Quercetin phytosome is a new food-grade lecithin-based formulation of quercetin, was developed to overcome the low bioavailability hurdle of quercetin. Phytosome complexes are created by a patented process that binds a botanical extract to a phospholipid (phosphatidylcholine), which are key components of every cell membrane.

Each capsule contains 250 mg of quercetin phytosome and 100 mg of bromelain.

BestReviews.com: Pricier than many similar products on the market

Amazon Best Sellers: #11 Best Seller in Flavonoid Vitamin Supplements. 4.7 out of 5 overall rating with more than 390 customer reviews.

Our Take: If you are looking to buy from a reputable brand, this would be your choice.

I have histamine intolerance and had spent many years taking prescription and OTC drugs. I wanted to get away from drugs and my functional medicine doctor recommended d-hist. It worked on my allergies but I would get migraines if I took it too often. I think it was the nettles. Anyway, I also didn't like that they used magnesium stearate. I bought this and it works just as well as my Claritin did. I get relief from runny nose and sneezing as well as itchy skin. I will sometimes add some extra bromelain but I am very happy. Thorne products are often more expensive but they use better ingredients and omit questionable ingredients that make production cheaper

4.8 out of 5 - 142 global ratings

Check Price on Amazon 

3Forest Leaf QuercetinBromelain, Stinging Nettle, Vitamin C



Uniquely formulated using a blend of quercetin and bromelain, this supplement from ForestLeaf may help with sinus relief, allergies, cardiovascular and respiratory health.

- Advanced Sinus and Allergy Supplement 
- Natural Vegetable Capsules 
- Non GMO, Dairy, Gluten, Egg and Nut Free 
- Every pill contains stinging nettle leaf extract. 
- All of its products and pills are tested for maximum absorption. 
- 45 servings per bottle, 200mg of vitamin C per serving.

Ingredients
Vitamin C 200mg, Quercetin 500mg, Stinging Nettle Leaf 500mg, Bromelain 150mg, Vegetable Cellulose (capsule), Microcrystalline Cellulose, Magnesium Stearate and Silicon Dioxide


I have year round allergies and lately what I had been taking wasn't working and my eyes were always running. It was extremely annoying and frustrating to be crying from one eye all day. I read the reviews and decided to try this. I've been taking them twice a day since March 1st and I stopped crying the first day. I love these natural pills. They work!!!!

4.6 out of 5 - 2,342 global ratings


4. Natural Factors Bioactive Quercetin


Natural Factors Bioactive Quercetin EMIQ claims to have 40 times better absorption than ordinary quercetin. Other quercetin supplements here use bromelain to boost bioavailability, but this supplement uses “EMIQ”, a proprietary formula made from “Enzymatically Modified IsoQuercetin”.

Dosage of quercetin is somewhat low (as compared to other brands) in each capsule. However, Natural Factors claims the quercetin is more bioavailable, which means your body gets a strong dose regardless. Each capsule contains 167 mg of EMIQ and 50 mg of vitamin C. Natural Factors claims their formula will provide year-round protection while supporting a healthy inflammatory response and maintaining good sinus and upper respiratory function.

Amazon Best Sellers: #25 Best Seller in Flavonoid Vitamin Supplements.

Amazon Review: "This literally took away all of my excessive histamine responses within a couple of hours. the second day got even better. If you suffer from allergies or inflammation and would like a natural option, please consider this." - Sparklebarbie

Our Take: Best Quercetin for Bioavailability

I’ve been on quercetin for a long time for bad allergies - the kind that requires MULTIPLE antihistamines. (Mast Cell Activation Disorder - basically your body releases too much histamine to too many stimulus). This quercetin is WAY more potent and WAY more effective than regular quercetin. I take a lot less of this, and only once a day, and it really helps my allergies. It’s a little spendy but well worth it due to it’s effectiveness. Also this is a good brand that I trust. I’ve been researching and taking supplements for more than 20 years, and this one brand I always feel comfortable recommending to others.

4.8 out of 5 - 490 global ratings


5. Mt Angel Vitamins Quercetin Zinc - Best Immune Support Supplement 



FORTIFIED FUNCTION – Sick of stuffy, sneezy, seasonal illnesses? Fight flare-ups with Mt. Angel Vitamins’ quercetin supplement! This nutrient blend helps boost better health so you can feel your best!

OVERALL AID – Bolster your body AND mind! Quercetin with vitamin C and zinc are proven not only to provide immune support but also to improve metabolism, circulatory supporty, and cognitive clarity!

BREATHE & BOUND – Revive your vitality! By fostering cellular functioning, your zinc quercetin capsules’ antioxidants enhance respiratory health and energy levels so you can enjoy activities!

TAKE IT EASY – Support, meet simplicity. To enjoy extra defense, take 1 of your quercetin with bromelain and zinc capsules twice daily. Bursting with 300 capsules, your bottle lasts longer than most brands’.

Our Take: Quercetin works best when taken with vitamin C and Bromelain, as vitamin C helps activate it and bromelain helps with the absorption. That’s why many quercetin supplements contain vitamin C or bromelain, as some evidence suggests they boost absorption.

Ratings
4.7 out of 5 - 1,105 global ratings

Reviews

My husband read the Swiss protocal for Covid 19 preventative and this has it all. So far so good no problems. No bad taste easy to swallow, our 12yr old son even has no priblem.

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6. Amazing Formulas - Quercetin 500 Mg



Amazon Best Sellers: #1 Best Seller in Flavonoid Vitamin Supplements. 4.7 out of 5 overall rating with more than 12,000 customer reviews.

- Quercetin is a flavonoid (plant pigment) naturally found in fruits and vegetables. It is found in many foods, such as red wine, onions, green tea, apples, berries etc. It known for its Anti-oxidant and Anti-Inflammatory Properties. Amazing Nutrition Quercetin 500 Mg is offered in Veggie Capsule to suit most diet preferences
- Anti-oxidant properties of Qurecetine Supports Healthy Ageing, Cardiovascular Health, and Immune Health. It helps to reduce the damage and irritation caused by free radicals
- Anti-Inflammatory properties of Quercetin helps to lower the release of histamines, a compound that is released by cells in response to allergic and inflammatory reactions. Subsequently helping to lower pains and discomfort related to Inflammation.
- All Amazing Nutrition products are manufactured in accordance with Good Manufacturing Practices (GMP), among the highest standards in the world.

I've been sick twice in the past two months, one a mild cold, the other quite severe, DID NOT GET TESTED so can not attest to Covid 19. Anyway, once I got sick, I took 1000mg of Quercetin, combined with 200mg of Zinc Picolinate - ANECDOTAL EVIDENCE: I was free and clear of symptoms in the range of 6 to 10 hours, save for a lingering itch in my sinuses, which was gone after a good nights sleep. Symptoms did not return in either case. This was ONE DOSE.

4.7 out of 5 - 15,071 global ratings


7. Whole Food Quercetin Plus



- Quercetin with Bromelain-Zinc-Vitamin C-Ginger-Bioflavonoids
- Organic Whole Foods
- Immune, Cardiovascular & Respiratory System Support
- Natural Antioxidant
- Vegan, Non-GMO
- 180 Caps, 90 servings

-Immunity supporting properties, improves healthy seasonal immune system function, and reduces inflammation.
- May help improve your daily health by aiding exercise performance, improving digestion, helping respiratory health, give your immune system the boost it needs, and enhance cognitive function.
- FREE from GMO, Alcohol, Preservatives, Soy Lecithin, Gelatin, Dairy, Sugar, Gluten, Shellfish, Nuts, Wheat, Stearates, Silicon Dioxide, fillers, Artificial Ingredients.
- Manufactured in the USA. Made in a GMP-certified facility in the USA. Third-party tested.

Nutrients
Quercetin 500 mg + 175 mg of Organic Whole Food Quercetin Blend(4 Organic Whole Food Quercetin source ingredients) + 15 mg of Zinc Picolinate + 200 mg of Bromelain from Pineapple + 100 mg of Organic Ginger Root + 125 mg of Vitamin C from Organic Acerola Cherries + 100 mg of Citrus Bioflavonoids from Organic Orange & Organic Lemon

Review
I am able to do much more before having to take a rest break. Also I have notice a very marked drop in BG an hour after taking. Definitely recommend.

Buy on Amazon


8. Doctor's Best Quercetin Bromelain




- Non-GMO, Vegan, Gluten Free, Soy Free
- 180 Veggie Caps
- Bromelain 3000 GDU per capsule, has 500 Mg of Quercetin with 250 Mg Bromelain for a Serving size of 2 Capsules
- Quercetin and Bromelain enhances each other's antioxidant and anti-inflammatory potential. Quercetin is a bioflavonoid that has potent antioxidants while bromelain works as protein-digesting enzyme. Bromelain helps increase your body’s absorption and use of Quercetin.
- Helps support immune health, heart health, joint comfort, healthy digestions, respiratory health and inflammatory response.
- Quercetin helps ensure appropriate immune response, inhibits formation of free radicals and promotes circulatory health in part by supporting the integrity of small blood vessels.

i have sleep apnea and have TO sit up in a recliner to sleep because i can not use a CPAP. QUERCETIN CLEARS MY SINUS SO BOTH NOSTRILS ARE OPENED WITH OUT ANY NEGATIVE PHARMCEUUTICAL DRUG SIDE EFFECTS . i now sleep lying flat. thank you drs best. you formula.

4.7 out of 5 - 2,096 global ratings


9. Nature's Life Bromelain Sinus Ease


Nature’s Life Bromelain Sinus Ease is formulated to help soothe sinuses and support optimal function of your nasal passages all year long. An enzyme naturally occurring in pineapples, bromelain may provide seasonal support to help keep you breathing easier and feeling well during the warm season and through the cold winter months. This groundbreaking complex works synergistically with quercetin (a bioflavonoid) and vitamin C, powerful antioxidants for healthy immune system support.

Perfect for seasonal support and great during the cold months, our vegetarian formula is designed to help maintain sinus and respiratory health.

- 1200mg with Vitamin C & Quercetin
- Sinus Health, Immune Function & Seasonal Support
- 100 Vegetarian Capsules
- Each serving contains 1200mg Bromelain Enzyme, 300mg Quercetin and 490mg Vitamin C
- Breathe Easy: May help support healthy respiratory function with bromelain
- Immune Function: Antioxidants in quercetin & vitamin C may provide powerful immune system support
- Gluten Free, Vegetarian
 
I have been suffering with sinus problems for years accompanied by constant facial pain and headaches. I have been using this product for about 10 days and it has now been 1 week since I have taken any medication for sinus problems. I am so grateful and amazed by this product.

4.5 out of 5 - 145 global ratings


10. Solaray QBC Plex



Intended to help support year round immune and respiratory health, Solaray QBC Plex is an effective blend of quercetin, bromelain, and Vitamin C. Quercetin may help support normal healthy sinus, respiratory and immune function. Bromelain is a plant enzyme known to help break down protein. Vitamin C provides antioxidant activity and is intended to help support normal, healthy collagen synthesis, capillary and blood vessel integrity, cartilage and bone development, immune function, and nerve impulse transmission.

Our QBC Plex brings together all three ingredients in a synergistic blend that will keep you feeling bright, healthy and vibrant all year long.

- Quercetin & Bromelain Plus Vitamin C
- Year Round Immune Function & Respiratory Health Support
- Non-GMO & Vegan
- 150 Count
- Trusted Brand: Manufactured in our own facility; Lab Verified for potency & purity

This is an amazing product, has helped me control my allergies (contact allergies to toiletries plus typical seasonal allergies) for decades now.

4.7 out of 5 - 335 global ratings


Benefits of Quercetin Supplements

Quercetin is a bioflavonoid found in certain fruits, vegetables, and grains. Bioflavonoids like quercetin provide benefits by working as antioxidants. 

You may already get a small amount of quercetin in your normal diet: quercetin is found in onions, kale, tomatoes, broccoli, asparagus, berries, red wine, citrus fruits, cherries, and tea. Many people also take quercetin in supplement form.

In fact, it’s estimated that the average person consumes about 10 to 100 mg of quercetin per day through a normal diet. Quercetin is one of the most abundant flavonoids in the human diet.

Quercetin is a pigment that belongs to a group of plant compounds called flavonoids (also known as bioflavonoids). Flavonoids are naturally present in fruits, grains, teas, and wine. Researchers have linked flavonoids to a variety of benefits, including a reduced risk of heart disease, cancer, and degenerative brain disorders.

What does science have to say about quercetin? Can quercetin really fight inflammation and reduce the risk of disease? Let’s dive into the science behind quercetin.

Quercetin has been shown to reduce inflammation in multiple studies. In this 8 week study involving 50 women with rheumatoid arthritis, participants took 500mg of quercetin per day or a placebo. The quercetin group reported less early morning stiffness, morning pain, and after-activity pain. 

Early studies on quercetin and inflammation are promising, although more large scale human studies need to be performed to verify these benefits.

There’s evidence that quercetin reduces allergy symptoms. Researchers believe quercetin’s anti-inflammatory effects may relieve allergy symptoms.

This study published in Molecules in 2016, for example, found that quercetin could be effective for treating the anaphylactic (allergic) reaction in someone with peanut allergies. A similar study from 2006 concluded that quercetin was a “safe, natural therapy that may be used as primary therapy or in conjunction with conventional methods” for blocking allergies. 

It’s possible that quercetin has the same anti-allergy effect in humans, although more research needs to be done.

There’s also some evidence that quercetin has cancer-fighting properties. Researchers believe quercetin can fight cancer cells with its powerful antioxidant properties.

In 2015, researchers reviewed available test tube and animal studies on quercetin and prostate cancer. After reviewing available evidence, researchers found that quercetin suppressed cell growth and induced cell death in prostate cancer cells.

This study published in 2017 in Oncology Reports took things a step further, finding that quercetin induced cancer cell death in nine types of cancer, including prostate cancer, colon cancer, and breast caner.

In another 2017 study, researchers gave quercetin to mice with tumors. Researchers found that mice in the quercetin-treated group showed delayed tumor growth, no significant changes in daily behavior, significantly better survival ratings, and increased rates of cell death.

Quercetin may also target bladder cancer. In 2016, researchers published a landmark study in the American Journal of Cancer Research. Researchers analyzed quercetin’s effect on cancer cells in a test tube. They concluded, “We are the first to show that quercetin displays potent inhibition on bladder cancer cells via activation of AMPK pathway.”

Early research on the cancer-fighting benefits of quercetin is promising, although more research needs to be performed to verify these effects in humans.

Other evidence suggests quercetin lowers your risk of chronic brain disorders, including Alzheimer’s and dementia.

In this study published in Neuropharmacology in 2015, researchers gave quercetin to mice with Alzheimer’s, injecting them with quercetin every two days for three months. By the end of the study, the injections had reversed several markers of Alzheimer’s, and the mice performed much better on learning tests.

In a separate study published in 2018, researchers gave mice with Alzheimer’s a quercetin-rich diet. Researchers found the diet improved brain function in mice with early-middle stage Alzheimer’s, although it had no significant effect on middle-late stage Alzheimer’s.

You may have heard that coffee is linked to a reduced risk of Alzheimer’s. There’s certainly some research to back that claim up. However, recent research has suggested that quercetin (not caffeine) is the primary compound in coffee responsible for protective effects against Alzheimer’s.

Some people use quercetin to reduce blood pressure and improve other measurements of cardiovascular health. High blood pressure raises your risk of heart disease, which is the leading cause of death in the United States. Approximately 1 in 3 American adults have high blood pressure.

Research suggests that quercetin reduces blood pressure levels. In this study published in 2002, researchers found that quercetin exhibited vasodilator effects, widening blood vessels and reducing blood pressure. 

Multiple studies on humans have suggested similar benefits. Researchers reviewed nine human studies involving 580 people. After reviewing available evidence, researchers found that taking more than 500 mg of quercetin supplement per day reduced systolic and diastolic blood pressure by 5.8mm Hg and 2.6 mm Hg, respectively. In other words, quercetin was shown to significantly improve blood pressure readings.

Some people take quercetin for its anti-aging effects. Antioxidants and anti-inflammatories – including quercetin – seem to have powerful anti-aging benefits. One study on young mice found that quercetin reduced mortality and extended lifespan. Another study from 2017 on human cells in test tubes found that quercetin reduced aging markers, with researchers concluding there was “anti-aging potential” for quercetin.

Others take quercetin supplements to improve endurance and exercise performance. This 2011 study reviewed 11 quercetin studies involving 254 human subjects and found that quercetin provided a statistically significant benefit in human endurance exercise capacity (VO2 max) and endurance exercise performance, although the effect “is between trivial and small”.

Finally, some diabetics take quercetin to help manage blood sugar. This study from 2019 found that taking 500mg of quercetin per day significantly reduced fasting plasma glucose (FPG) levels, suggesting that quercetin helped control fasting blood sugar. This study in 2019 found similar results, finding that quercetin lowered serum glucose levels at doses of 10, 25, and 50mg per kg.

Some suggest that quercetin could treat the COVID-19 coronavirus. Quercetin was shown to be effective against SARS, the Ebola virus, and the Zika virus. This 2019 study by researchers in Korea found that quercetin and other flavonoids may inhibit the proteolytic activity of SARS-CoV 3C-like protease, creating an antiviral effect. 

Read More: Quercetin and COVID-19

Dosage

Most quercetin studies use a dosage of around 500mg per day, although some studies use a dosage of 500mg taken twice per day.

Most supplements have a similar dosage, offering 500mg to 1,200mg of quercetin per serving.

In some studies, researchers have given participants up to 5,000mg of quercetin per day with no reported side effects.

Quercetin has poor bioavailability. You might take a 1,200mg quercetin supplement, but your body only absorbs a small percentage of it. That’s why many quercetin supplements contain vitamin C or bromelain, as some evidence suggests they boost absorption.

There’s also some evidence that quercetin has a synergistic effect when combined with other flavonoid supplements. That’s why some quercetin supplements contain resveratrol, catechins, genistein, and other flavonoids.

Quercetin Side Effects

Quercetin is generally recognized as safe. It’s found in many fruits and vegetables, and most people will experience no side effects when taking normal dosages of quercetin.

There have been few reported side effects for quercetin supplements.

In some studies, large doses of quercetin (over 1,000mg) were linked with headaches, digestive issues, and tingling sensations. However, these symptoms were mild and uncommon.

Quercetin from food sources is safe for pregnant and breastfeeding women to take. However, there’s limited research on quercetin supplements in pregnant or breastfeeding women.

There’s no evidence that quercetin interacts with any drugs in a significant way. However, you should talk to your doctor before taking quercetin, especially if you are taking antibiotics or blood pressure medication.

Frequently Asked Questions About Quercetin

This section will help to answer some of the most commonly asked questions about Quercetin.

What are the best foods for quercetin?

A: Capers, peppers (yellow and green), onions (red and white), shallots, asparagus, cherries, tomatoes, red apples, red grapes, broccoli, kale, red leaf lettuce, cranberries, blueberries, raspberries, green tea, black tea, and coffee are all excellent foods for quercetin.

Quercetin Dihydrate vs Quercetin

The key difference between quercetin and quercetin dihydrate is that quercetin is a plant flavonoid, whereas quercetin dihydrate is a synthetic chemical compound. Moreover, quercetin is a yellow crystalline powder, whereas quercetin dihydrate is a bright yellow colour powder.

Quercetin Dihydrate has the highest bioavailability when it comes to quercetin supplements.

According to Examine.com, this form is preferable to glycosides, aglycone and rutinoside versions.


On its own, quercetin has a low bioavailability, which means your body absorbs it poorly.

That’s why the supplements may include other compounds, such as vitamin C or digestive enzymes like bromelain, as they may increase absorption.

Additionally, some research indicates that quercetin has a synergistic effect when combined with other flavonoid supplements, such as resveratrol, genistein, and catechins.

A new food-grade lecithin-based form of quercetin, Quercetin Phytosome, was developed and validated in healthy volunteers. Quercetin Phytosome overcomes the low bioavailability hurdle of quercetin and should help to fulfill the great health benefit potential of this flavonoid in the diet and as food supplements.

Most in vitro studies used a form of quercetin called 'quercetin aglycone'. However, this particular form of quercetin is never found in the blood, even after ingested, as it it gets changed in the liver.

According to Examine, the quercetin dihydrate form has the apparent best bioavailability followed by glycosides, aglycone, and finally rutinoside.


Most of the quercetin ingredients on the market are in the quercetin dihydrate form. Quercetin anhydrous and dihydrate differ in the amount of water they contain. Quercetin anhydrous contains only 1% to 4% moisture and the sugar molecules that are attached to quercetin in its natural form have been extracted. This translates into 13% more quercetin per gram for quercetin anhydrous vs quercetin dihydrate. For formula manufacturers, this means there is substantially less bulk per capsule or tablet.

Rutin vs Quercetin

Often referred to as “Vitamin P”, Rutin is comprised of a quercetin molecule bound to a sugar molecule called rutinose. It is chemically very similar to Quercetin and the two compounds are invariably found together in fruits and vegetables.

An animal study published in the Nature (Aug 2012), concluded that rutin exerts stronger protection against liver damage but has weaker antioxidant and anti-inflammatory activities and antifibrotic (anti-scarring) potential than quercetin

Another study (JCI May 2012) on rutin, commonly found in fruits and vegetables and sold over the counter as a dietary supplement, has been shown to inhibit the formation of blood clots in an animal model of thrombosis.

Do you get enough quercetin in your daily diet?

A: The average person gets 10 to 100 mg of quercetin per day through normal dietary sources. This can vary greatly. Carefully track your diet over an extended period to figure out if you have a dietary deficiency of quercetin.

How much quercetin should you take per day?

A: Researchers typically use a dose of 500 mg of quercetin per day in supplement form. Most quercetin supplements contain between 500 and 1200 mg of quercetin, although this can vary. Check out the nutritional label for your quercetin supplement to be sure.

Does quercetin help allergies?

A: Many people take quercetin supplements to avoid allergy symptoms. There’s evidence that quercetin has powerful anti-allergy benefits, although more research needs to be done.

Q: Does quercetin fight cancer?

A: Early research in test tube and animal models shows that quercetin may have cancer-fighting properties. While these findings are promising, more large scale human studies need to be performed. Research is not definitive. Consult your physician before using any supplement to improve your cancer.

Q: Does quercetin reduce the risk of Alzheimer’s?

A: Studies show that quercetin may reduce the onset of Alzheimer’s, particularly in the early and middle stages of the condition. However, studies have mostly been performed on mice and test tubes – not in humans.

Q: What are other names for quercetin?

A: Quercetin goes by a number of different names. You might see quercetin supplements labeled as bioflavonoid concentrate, bioflavonoid extract, or citrus bioflavonoid, for example.

Q: Can quercetin help you recover after exercise?

A: Some studies show that quercetin boosts recovery after exercise. In some small studies, athletes taking quercetin after exercise had faster recovery than a control group. Researchers believe quercetin reduces oxidative stress and post-exercise inflammation, helping your body recover.

Q: What are the side effects of quercetin?

A: Most people experience no side effects from quercetin, and any side effects tend to be mild. Quercetin side effects include tingling and numbness, headache, and nausea. Your chance of experiencing side effects increases at higher dosages (over 1,000mg).

Q: Why do so many quercetin supplements contain bromelain?

A: Bromelain is a naturally occurring, protein-digesting enzyme found in the stem of the pineapple. Bromelain seems to boost the absorption of quercetin by inhibiting inflammatory chemicals called prostaglandins. Bromelain may also decrease inflammation on its own.

Your body doesn’t absorb quercetin very effectively on its own. Some studies have shown that bromelain boosts the absorption of quercetin, which is why you find bromelain (or vitamin C) in many quercetin supplements.

Q: What’s the difference between rutin or glycosidic quercetin?

A: Quercetin is found in two forms, including in rutin or glycosidic form. Quercetin glucosides, such as isoquercitrin and isoquercetin, seem to be much more bioavailable and more quickly absorbed than quercetin aglycone or quercetin glycosides, such as rutin (quercetin rutinoside).

Q: Can you overdose on quercetin?

A: In one study, researchers gave participants 2,000mg to 5,000mg of quercetin per day with no adverse effects or signs of toxicity reported. Generally, quercetin is safe to take even in high doses, although you may experience mild side effects like nausea, digestive issues, and headaches at high doses. Excessively high doses of quercetin could lead to kidney problems.

Q: How much quercetin should you take for hay fever?

A: Experts recommend taking 400mg of quercetin twice a day between meals for hay fever. Also consult your doctor to help provide a more comprehensive and effective treatment for hay fever.

Q: Can children take quercetin?

A: Most studies suggest that it’s safe to give quercetin to your child, although you should use only half the dose you'd use on an adult. Talk to your pediatrician before giving any quercetin to your child.

Q: How does quercetin manage allergy symptoms?

A: Studies have shown that quercetin stabilizes mast cells that release histamine. Histamine is the principal mediator of reactions to pollen and other allergies. This makes quercetin a natural antihistamine. Many people use quercetin to treat symptoms of hay fever, including runny nose, watering eyes, and itching.

Q: Can you take too much quercetin?

A: You should start with a quercetin dosage of around 500mg per day to assess your tolerance. However, researchers have given participants up to 5,000mg of quercetin per day with few reported side effects. Look for symptoms like upset stomach and diarrhea. Excessively high doses of quercetin could lead to kidney problems.

Q: Who should not take a quercetin supplement?


A: Quercetin appears safe for anyone to take when used in normal dosages. However, there’s limited research on how quercetin supplements affect women who are pregnant or breastfeeding. People with high blood pressure, or anyone taking blood pressure medication, may also want to take to their doctor before taking a quercetin supplement.

Q: Can you take a quercetin supplement with a pineapple allergy?

A: If you’re allergic to pineapples, you should avoid quercetin supplements with bromelain. Bromelain, an enzyme in pineapples, is added to quercetin supplements to boost bioavailability. Overuse of bromelain can create problems for consumers.

Q: Does quercetin work for anti-aging?

A: Several studies have examined the effect of quercetin on aging. Quercetin is rich with anti-inflammatories and antioxidants, which could make it a powerful anti-aging compound. 

Q: Does quercetin help asthma?

A: Quercetin may help asthma by relaxing smooth muscles lining the airway, improving airway flow.

Q: What’s better – quercetin tablets, capsules, powders, or liquid?

A: Quercetin liquid claims to be more bioavailable than other sources of quercetin. You take the liquid sublingually (underneath your tongue). However, limited research shows quercetin capsules or powders are more effective, and all forms of quercetin are absorbed poorly by the body.

Q: Where does quercetin come from?

A: Most supplement companies use various plant or vegetable-based sources of quercetin. Check the label.

Q: Can you get citrus-free quercetin?

A: Some quercetin supplements are specifically marketed as citrus-free, making them ideal for those with citrus sensitivities. Read the label or official product website for your supplement to be sure that it is actually citrus-free.

Q: Does quercetin help with diabetes?

A: There’s some evidence that quercetin helps with diabetes, helping your body manage blood sugar levels during fasting. However, more research needs to be done to verify these benefits.

Q: Is quercetin non-GMO?

A: Quercetin supplements are generally labeled non-GMO. Check the label to verify your quercetin supplement is not made from genetically modified ingredients.

Wrapping It Up

Quercetin is a bioflavonoid with potent antioxidant and anti-inflammatory effects. Many take quercetin supplements daily to support various body systems.

Some people take quercetin supplements for allergies. Others take it to boost the immune system. Others take quercetin for general anti-aging or health and wellness.

Early research on quercetin is promising, and new human studies are released every year validating certain quercetin benefits. 

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Here is the list of nutrients and their respective directions based on the FLCCC and Dr Zelenko's prevention protocol.
  • Nature's Bounty Vitamin D3 - 2,000 IU > One dose daily (Amazon)
  • Nature's Bounty Vitamin C - 1,000 mg > One caplet twice daily (Amazon)
  • Now Foods Quercetin - 400 mg > One capsule daily (Amazon)
  • Nature's Bounty Melatonin 5 mg > One tablet before bedtime (Amazon)
  • Nature's Bounty Zinc 50 mg/day > One caplet daily (Amazon)
Be aware that most of the dosages are above the recommended daily value and therefore should not be taken on a long term basis. 

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