QUERCETIN Overview Information
Quercetin is a plant pigment (flavonoid). It is found in many plants and foods, such as red wine, onions, green tea, apples, berries, Ginkgo biloba, St. John's wort, American elder, and others. Buckwheat tea has a large amount of quercetin. People use quercetin as a medicine.
Quercetin is used for treating conditions of the heart and blood vessels including “hardening of the arteries” (atherosclerosis), high cholesterol, heart disease, and circulation problems. It is also used for diabetes, cataracts, hay fever, peptic ulcer, schizophrenia, inflammation, asthma, gout, viral infections, chronic fatigue syndrome (CFS), preventing cancer, and for treating chronic infections of the prostate. Quercetin is also used to increase endurance and improve athletic performance.
How does it work?
Quercetin has antioxidant and anti-inflammatory effects which might help reduce prostate inflammation.
QUERCETIN Uses & Effectiveness 
Possibly Effective for:
- Prostate pain and swelling (inflammation). Taking quercetin by mouth seems to reduce pain and improve quality of life, but doesn’t seem to help urination problems in men with ongoing prostate problems that aren’t due to infection.
Insufficient Evidence for:
- Heart disease. Limited research suggests that increasing dietary intake of quercetin might help prevent heart disease death in elderly men.
- High cholesterol. Short-term use of quercetin supplements does not seem to lower “bad cholesterol” (low-density lipoprotein (LDL) cholesterol), lower total cholesterol, or raise “good cholesterol” (high-density lipoprotein (HDL) cholesterol).
- High blood pressure. Some research suggest that 365mg of quercetin aglycone twice daily produces a small (5-7 mmHg) decrease in blood pressure in people with untreated, mild high blood pressure. It’s not known yet how important this is.
- Exercise-induced respiratory infections. Developing research shows that taking 500 mg of quercetin twice daily for 3 weeks before, and continuing during 3 days of extended, intense cycling reduces the number of upper respiratory infections in the 14 days following the heavy exercise.
- Kidney transplantation. Some research suggests that a combination of 20 mg of quercetin and 480 mg of curcumin taken once or twice daily, starting within 24 hours of kidney transplantation and continuing for one month, in combination with anti-rejection drugs, improves early function of the transplanted kidney.
- Exercise endurance.
- “Hardening of the arteries” (atherosclerosis).
- Diabetes.
- Cataracts.
- Hay fever (allergic rhinitis).
- Stomach and intestinal ulcers.
- Schizophrenia.
- Pain and swelling (inflammation).
- Asthma.
- Gout.
- Viral infections.
- Chronic fatigue syndrome (CFS).
- Cancer.
- Other conditions.
QUERCETIN Side Effects & Safety
Quercetin is POSSIBLY SAFE for most people when taken by mouth short-term. Quercetin has been safely used in amounts up to 500 mg twice daily for 12 weeks. It is not known if longer-term use or larger amounts are safe.
Quercetin can cause headache and tingling of the arms and legs. Very high doses might cause kidney damage.
When given intravenously (by IV) in appropriate amounts (less than 722 mg), quercetin is POSSIBLY SAFE. But larger amounts given by IV are POSSIBLY UNSAFE. There have been reports of kidney damage at higher doses.
Special Precautions & Warnings:
Pregnancy and breast-feeding: Not enough is known about the use of quercetin during pregnancy and breast-feeding. Stay on the safe side and avoid use.QUERCETIN Interactions
Moderate Interaction Be cautious with this combination
- Antibiotics (Quinolone antibiotics) interacts with QUERCETIN
Taking quercetin along with some antibiotics might decrease the effectiveness of some antibiotics. Some scientists think that quercetin might prevent some antibiotics from killing bacteria. But it's too soon to know if this is a big concern.
Some of these antibiotics that might interact with quercetin include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), trovafloxacin (Trovan), and grepafloxacin (Raxar). - Cyclosporin (Neoral, Sandimmune) interacts with QUERCETIN
Cyclosporin (Neoral, Sandimmune) is changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down cyclosporin (Neoral, Sandimmune). Taking quercetin might increase the effects and side effects of this medication. Before taking quercetin talk to your healthcare provider if you take cyclosporin (Neoral, Sandimmune).
- Medications changed by the liver (Cytochrome P450 2C8 (CYP2C8) substrates) interacts with QUERCETIN
Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with these medications that are changed by the liver might increase the effects and side effects of your medication. Before taking quercetin talk to your healthcare provider if you take any medications that are changed by the liver.
Some medications that are changed by the liver include paclitaxel (Taxol), rosiglitazone (Avandia), amiodarone (Cordarone), docetaxel (Taxotere), repaglinide (Prandin), verapamil (Calan, Isoptin, Verelan), and others. - Medications changed by the liver (Cytochrome P450 2C9 (CYP2C9) substrates) interacts with QUERCETIN
Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with these medications that are changed by the liver might increase the effects and side effects of your medication. Before taking quercetin talk to your healthcare provider if you take any medications that are changed by the liver.
Some medications that are changed by the liver include celecoxib (Celebrex), diclofenac (Voltaren), fluvastatin (Lescol), glipizide (Glucotrol), ibuprofen (Advil, Motrin), irbesartan (Avapro), losartan (Cozaar), phenytoin (Dilantin), piroxicam (Feldene), tamoxifen (Nolvadex), tolbutamide (Tolinase), torsemide (Demadex), warfarin (Coumadin), and others. - Medications changed by the liver (Cytochrome P450 2D6 (CYP2D6) substrates) interacts with QUERCETIN
Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with these medications that are changed by the liver might increase the effects and side effects of your medication. Before taking quercetin talk to your healthcare provider if you take any medications that are changed by the liver.
Some medications that are changed by the liver include amitriptyline (Elavil), codeine, flecainide (Tambocor), haloperidol (Haldol), imipramine (Tofranil), metoprolol (Lopressor, Toprol XL), ondansetron (Zofran), paroxetine (Paxil), risperidone (Risperdal), tramadol (Ultram), venlafaxine (Effexor), and others. - Medications changed by the liver (Cytochrome P450 3A4 (CYP3A4) substrates) interacts with QUERCETIN
Some medications are changed and broken down by the liver. Quercetin might decrease how quickly the liver breaks down some medications. Taking quercetin along with these medications that are changed by the liver might increase the effects and side effects of your medication. Before taking quercetin talk to your healthcare provider if you take any medications that are changed by the liver.
Some medications that are changed by the liver include lovastatin (Mevacor), clarithromycin (Biaxin), cyclosporine (Neoral, Sandimmune), diltiazem (Cardizem), estrogens, indinavir (Crixivan), triazolam (Halcion), verapamil (Calan, Isoptin, Verelan), alfentanil (Alfenta), fentanyl (Sublimaze), losartan (Cozaar), fluoxetine (Prozac), midazolam (Versed), omeprazole (Prilosec), lansoprazole (Prevacid), ondansetron (Zofran), propranolol (Inderal), fexofenadine (Allegra), amitriptyline (Elavil), amiodarone (Cordarone), citalopram (Celexa), sertraline (Zoloft), ketoconazole (Nizoral), itraconazole (Sporanox), and numerous others. - Medications moved by pumps in cells (P-glycoprotein Substrates)) interacts with QUERCETIN
Some medications are moved by pumps in cells. Quercetin might make these pumps less active and increase how much of some medications get absorbed by the body. This might cause more side effects from some medications.
Some medications that are moved by these pumps include diltiazem (Cardizem), verapamil (Calan, Isoptin, Verelan), digoxin (Lanoxin) cyclosporine (Neoral, Sandimmune), saquinavir (Invirase), amprenavir (Agenerase), nelfinavir (Viracept), loperamide (Imodium), quinidine, paclitaxel (Taxol), vincristine, etoposide (VP16, VePesid), cimetidine (Tagamet), ranitidine (Zantac), fexofenadine (Allegra), ketoconazole (Nizoral), itraconazole (Sporanox), and others.
QUERCETIN Dosing
The following dose has been studied in scientific research:
BY MOUTH:
- For prostate pain and swelling (prostatitis): 500 mg twice daily.
