Quercetin

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What is it?

Quercetin is a plant pigment (flavonoid). It’s found in many plants and foods, such as red wine, onions, green tea, apples, and berries.

Quercetin has antioxidant and anti-inflammatory effects that might help reduce swelling, kill cancer cells, control blood sugar, and help prevent heart disease.

Quercetin is most commonly used for conditions of the heart and blood vessels and to prevent cancer. It is also used for arthritis, bladder infections, and diabetes, but there is no strong scientific evidence to support most of these uses. There is also no good evidence to support using quercetin for COVID-19.

It is effective?
Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

Possibly Ineffective for …

  • Athletic performance. Taking quercetin by mouth before exercise doesn’t decrease fatigue or improve exercise ability.

There is interest in using quercetin for a number of other purposes, but there isn’t enough reliable information to say whether it might be helpful.

Is there concern for the safety of its use?
When taken by mouth: Quercetin is possibly safe for most people when used short-term. Quercetin has been safely used in doses up to 1 gram daily for 12 weeks. It’s not known if long-term use or higher doses are safe.

When applied to the skin: There isn’t enough reliable information to know if quercetin is safe or what the side effects might be.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn’t enough reliable information to know if quercetin is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Kidney problems: Quercetin might make kidney problems worse. Don’t use quercetin if you have kidney problems.

Are there any drug interactions?

Antibiotics (Quinolone antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

Some scientists think that taking quercetin along with certain antibiotics, called quinolone antibiotics, might decrease the effects of these antibiotics. But it’s too soon to know if this is a big concern.

Cyclosporine (Neoral, Sandimmune)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might decrease how quickly the body breaks down cyclosporine. Taking quercetin with cyclosporine might increase the effects and side effects of cyclosporine.

Diclofenac (Voltaren, others)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might decrease how quickly the body breaks down diclofenac. Taking quercetin with diclofenac might increase the effects and side effects of diclofenac.

Losartan (Cozaar)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might change how the body absorbs and breaks down losartan. Taking quercetin with losartan might change the effects and side effects of losartan.

Medications changed by the liver (Cytochrome P450 2C8 (CYP2C8) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Quercetin might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Quercetin might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 2D6 (CYP2D6) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Quercetin might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are changed and broken down by the liver. Quercetin might change how quickly the liver breaks down these medications. This could change the effects and side effects of these medications.

Medications for diabetes (Antidiabetes drugs)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might lower blood sugar levels. Taking quercetin along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.

Medications for high blood pressure (Antihypertensive drugs)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might lower blood pressure. Taking quercetin along with medications that lower blood pressure might cause blood pressure to go too low. Monitor your blood pressure closely.

Medications moved by pumps in cells (Organic Anion Transporter 1 (OAT1) Substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are moved in and out of cells by pumps. Quercetin might change how these pumps work and change how much medication stays in the body. In some cases, this might change the effects and side effects of a medication.

Medications moved by pumps in cells (Organic Anion Transporter 3 (OAT3) Substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are moved in and out of cells by pumps. Quercetin might change how these pumps work and change how much medication stays in the body. In some cases, this might change the effects and side effects of a medication.

Medications moved by pumps in cells (Organic anion-transporting polypeptide substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are moved in and out of cells by pumps. Quercetin might change how these pumps work and change how much medication stays in the body. In some cases, this might change the effects and side effects of a medication.

Medications moved by pumps in cells (P-glycoprotein substrates)

Interaction Rating=Moderate Be cautious with this combination.

Some medications are moved in and out of cells by pumps. Quercetin might change how these pumps work and change how much medication stays in the body. In some cases, this might change the effects and side effects of a medication.

Midazolam (Versed)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might increase how quickly the body breaks down midazolam. Taking quercetin with midazolam might reduce the effects of midazolam.

Mitoxantrone

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might increase levels of mitoxantrone. Taking quercetin and mitoxantrone together might increase the effects and side effects of mitoxantrone.

Pravastatin (Pravachol)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might decrease how quickly the body gets rid of pravastatin. Taking quercetin with pravastatin might increase the effects and side effects of pravastatin.

Prazosin (Minipress)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might increase levels of prazosin. Taking quercetin and prazosin together might increase the effects and side effects of prazosin.

Quetiapine (Seroquel)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might increase levels of quetiapine. Taking quercetin and quetiapine together might increase the effects and side effects of quetiapine.

Sulfasalazine (Azulfidine)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might increase levels of sulfasalazine. Taking quercetin and sulfasalazine together might increase the effects and side effects of sulfasalazine.

Warfarin (Coumadin)

Interaction Rating=Moderate Be cautious with this combination.

Quercetin might increase the effects that warfarin has on the body. Taking quercetin and warfarin together might increase the effects and side effects of warfarin, which could increase the risk of bruising and bleeding.

Are there any interactions with herbs and supplements?
Herbs and supplements that might lower blood pressure: Quercetin might lower blood pressure. Taking it with other supplements that have the same effect might cause blood pressure to drop too much. Examples of supplements with this effect include andrographis, casein peptides, L-arginine, niacin, and stinging nettle.
Herbs and supplements that might lower blood sugar: Quercetin might lower blood sugar. Taking it with other supplements with similar effects might lower blood sugar too much. Examples of supplements with this effect include aloe, bitter melon, cassia cinnamon, chromium, and prickly pear cactus.

Are there any interactions with food?
There are no known interactions with foods.

What dose is used?
Quercetin has most often been used by adults in doses of 250-1000 mg by mouth daily for up to 12 weeks. Speak with a healthcare provider to find out what dose might be best for a specific condition.

By what other names is the product known?
3,3′,4’5,7-Pentahydroxyflavone, Bioflavonoid, Bioflavonoid Complex, Bioflavonoid Concentrate, Bioflavonoid Extract, Bioflavonoïde, Bioflavonoïde de Citron, Bioflavonoïdes de Citron, Citrus Bioflavones, Citrus Bioflavonoid, Citrus Bioflavonoids, Citrus Bioflavonoid Extract, Citrus Flavones, Citrus Flavonoids, Complexe de Bioflavonoïde, Concentré de Bioflavonoïde, Extrait de Bioflavonoïde, Extrait de Bioflavonoïdes de Citron, Flavones de Citron, Flavonoid, Flavonoïde, Meletin, Mélétine, Quercetina, Quercétine, Sophretin, Sophrétine.

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