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The data behind the verdict
Corpus · initializing
93+ interactions across 20 supplements
Cross-reference any supplement against your medications. Severity grades follow Examine’s peer-reviewed framework.
Dangerous (3)
Warfarin (Coumadin)
Omega-3 inhibits platelet aggregation, producing an additive anticoagulant effect on top of warfarin.
What to do: Monitor INR closely. Reduce dose if INR rises.
Source: PMID: 25062404
Clopidogrel (Plavix)
Dual antiplatelet effect.
What to do: Monitor for unusual bruising or bleeding.
Source: FDA label
High-dose Aspirin
Additive antiplatelet effect.
What to do: Use caution at omega-3 doses above 3g per day.
Source: Clinical consensus
Moderate (2)
Blood pressure medications
Omega-3 may lower BP modestly.
What to do: Monitor BP when starting omega-3.
Source: Clinical consensus
Orlistat (Alli)
Reduces fat absorption, including omega-3.
What to do: Separate by 2 or more hours.
Source: FDA label
The most interaction-prone supplement in common use. St. John's Wort induces multiple drug-metabolism enzymes and can cause treatment failure across many drug classes.
Dangerous (10)
SSRIs (Prozac, Zoloft, Lexapro)
Additive serotonergic effect.
What to do: Never combine.
Source: PMID: 27444983
SNRIs (Effexor, Cymbalta)
Additive serotonergic effect.
What to do: Never combine.
Source: FDA warning
Oral contraceptives
Induces CYP3A4, accelerating estrogen metabolism.
What to do: Never combine. Use backup contraception.
Source: PMID: 19719333
Cyclosporine
Induces CYP3A4, dramatically reducing cyclosporine levels.
What to do: Absolutely never combine.
Source: FDA black box warning
HIV protease inhibitors (ritonavir, indinavir)
Induces CYP3A4, reducing drug levels.
What to do: Never combine.
Source: FDA warning
Warfarin
Induces CYP enzymes, reducing warfarin levels.
What to do: Never combine.
Source: PMID: 19719333
Digoxin
Induces P-glycoprotein, reducing digoxin levels.
What to do: Never combine.
Source: Clinical pharmacology
Chemotherapy agents
Induces CYP3A4, reducing drug levels.
What to do: Never combine.
Source: FDA warning
Theophylline
Induces CYP1A2, reducing levels.
What to do: Avoid.
Source: Clinical pharmacology
Triptans (sumatriptan)
Additive serotonergic effect.
What to do: Avoid.
Source: FDA warning
Moderate (6)
Levothyroxine (Synthroid)
Magnesium binds levothyroxine in the gut, reducing absorption.
What to do: Separate by 4 or more hours.
Source: FDA label
Fluoroquinolone antibiotics (Cipro, Levaquin)
Magnesium chelates the antibiotic.
What to do: Take 2+ hours before or 6+ hours after the antibiotic.
Source: FDA label
Tetracycline antibiotics
Magnesium chelates the antibiotic.
What to do: Separate by 2 to 3 hours.
Source: FDA label
Bisphosphonates (Fosamax, Boniva)
Magnesium reduces bisphosphonate absorption.
What to do: Take bisphosphonate first; magnesium 2 or more hours later.
Source: FDA label
Muscle relaxants and sedatives
Additive CNS depression.
What to do: Use caution, especially with magnesium taken at night.
Source: Clinical consensus
Potassium-sparing diuretics
Both raise serum magnesium and potassium.
What to do: Monitor electrolytes.
Source: Clinical pharmacology
Moderate (6)
Levothyroxine (Synthroid)
Calcium binds levothyroxine in the gut.
What to do: Separate by 4 or more hours.
Source: FDA label
Tetracycline and doxycycline
Calcium chelates the antibiotic.
What to do: Separate by 2 to 3 hours.
Source: FDA label
Fluoroquinolones (Cipro)
Calcium chelates the antibiotic.
What to do: Take 2+ hours before or 6+ hours after the antibiotic.
Source: FDA label
Iron supplements
Calcium blocks iron absorption.
What to do: Take at different meals.
Source: Clinical consensus
Bisphosphonates (Fosamax)
Calcium blocks bisphosphonate absorption.
What to do: Take bisphosphonate on an empty stomach; calcium later.
Source: FDA label
Thiazide diuretics (HCTZ)
Both increase serum calcium.
What to do: Monitor calcium levels.
Source: Clinical pharmacology
Vitamin K is the direct pharmacological antagonist of warfarin. Supplementing without cardiology supervision can cause dangerous clots.
Dangerous (1)
Warfarin (Coumadin)
Vitamin K reactivates clotting factors II, VII, IX, and X, directly opposing warfarin.
What to do: Keep vitamin K intake consistent (do not suddenly increase or decrease). Do not supplement vitamin K without cardiologist approval.
Source: FDA label, clinical standard
Moderate (4)
Warfarin and other anticoagulants
High-dose vitamin E (over 400 IU) inhibits platelet aggregation.
What to do: Limit to under 400 IU per day if on anticoagulants. Monitor INR.
Source: Clinical pharmacology
Aspirin and NSAIDs
Additive antiplatelet effect.
What to do: Use caution at high doses.
Source: Clinical consensus
Chemotherapy (alkylating agents)
Vitamin E is an antioxidant that may protect cancer cells from oxidative damage.
What to do: Avoid during active chemo. Discuss with your oncologist.
Source: Theoretical, debated
Statins combined with niacin
High-dose vitamin E may blunt the HDL-raising effect of the statin-niacin combo.
What to do: Clinical significance unclear.
Source: Limited evidence
Moderate (6)
Levothyroxine
Iron binds levothyroxine in the gut.
What to do: Separate by 4 or more hours.
Source: FDA label
Antacids, PPIs, H2 blockers
Reduced stomach acid impairs iron absorption.
What to do: Take iron on an empty stomach or with vitamin C. Separate from antacids by 2 or more hours.
Source: Clinical standard
Tetracycline and doxycycline
Iron chelates the antibiotic.
What to do: Separate by 2 to 3 hours.
Source: FDA label
Fluoroquinolones
Iron chelates the antibiotic.
What to do: Take 2+ hours before or 6+ hours after the antibiotic.
Source: FDA label
Levodopa (Parkinson's)
Iron reduces levodopa absorption.
What to do: Separate by 2 or more hours.
Source: Clinical pharmacology
Methyldopa
Iron reduces absorption.
What to do: Separate by 2 or more hours.
Source: FDA label
Moderate (4)
Fluoroquinolone antibiotics
Zinc chelates the antibiotic.
What to do: Take 2+ hours before or 6+ hours after the antibiotic.
Source: FDA label
Tetracycline antibiotics
Zinc chelates the antibiotic.
What to do: Separate by 2 to 3 hours.
Source: FDA label
Penicillamine (Wilson's disease)
Zinc reduces absorption.
What to do: Separate by 2 or more hours.
Source: FDA label
Copper (chronic high-dose zinc)
Zinc over 40mg/day induces metallothionein, which sequesters copper.
What to do: If taking zinc over 40mg/day for more than 8 weeks, supplement with 2mg copper.
Source: Clinical standard
Moderate (5)
Warfarin and other anticoagulants
Curcumin has antiplatelet properties.
What to do: Monitor INR. Avoid high-dose curcumin (over 500mg) on warfarin.
Source: Clinical pharmacology
Aspirin and NSAIDs
Additive antiplatelet and GI effects.
What to do: Use caution.
Source: Clinical consensus
Diabetes medications (metformin, sulfonylureas)
Curcumin lowers blood glucose.
What to do: Monitor blood sugar when adding curcumin.
Source: PMID: 34956436
CYP3A4 substrates
Curcumin inhibits CYP3A4 in vitro.
What to do: Use caution with narrow-therapeutic-index drugs; clinical significance uncertain.
Source: In vitro data
Tacrolimus or cyclosporine
CYP3A4 inhibition may raise levels.
What to do: Avoid or monitor drug levels.
Source: Theoretical
Moderate (5)
Levothyroxine and thyroid medications
Ashwagandha increases thyroid hormone production (TSH, T3, T4).
What to do: Monitor thyroid function. Dose adjustment may be needed.
Source: PMID: 28829155
Immunosuppressants (cyclosporine, tacrolimus, prednisone)
Ashwagandha stimulates immune function.
What to do: Avoid in transplant patients and autoimmune patients.
Source: Clinical pharmacology
Sedatives and benzodiazepines (Xanax, Valium)
Additive CNS depression.
What to do: Use caution. Reduce ashwagandha dose if you feel drowsy.
Source: Clinical consensus
Diabetes medications
Ashwagandha may lower blood glucose.
What to do: Monitor blood sugar.
Source: Clinical consensus
Blood pressure medications
Ashwagandha may lower BP.
What to do: Monitor BP.
Source: Clinical consensus
Dangerous (2)
Metformin
Berberine and metformin lower blood glucose via similar pathways.
What to do: Start at 500mg berberine. Monitor glucose closely. Metformin dose may need to be reduced.
Source: PMID: 37439907
Cyclosporine
Berberine inhibits CYP3A4 and P-glycoprotein, dramatically increasing cyclosporine levels.
What to do: Never combine without transplant team supervision.
Source: Clinical pharmacology
Moderate (5)
CYP2D6 substrates (codeine, tramadol, many antidepressants)
Berberine inhibits CYP2D6.
What to do: Monitor for side effects.
Source: PMID: 38928095
CYP3A4 substrates (statins, calcium channel blockers)
Berberine inhibits CYP3A4.
What to do: Use caution with narrow-therapeutic-index drugs.
Source: PMID: 37439907
Sulfonylureas (glipizide, glyburide)
Additive glucose lowering.
What to do: Monitor blood sugar closely.
Source: Clinical consensus
Blood pressure medications
Berberine may lower BP.
What to do: Monitor BP.
Source: Clinical consensus
Anticoagulants
Berberine may have antiplatelet effects.
What to do: Monitor if combining.
Source: Limited evidence
Moderate (4)
Warfarin
CoQ10 is structurally similar to vitamin K and may reduce warfarin efficacy.
What to do: Monitor INR when starting or stopping CoQ10.
Source: Clinical pharmacology
Blood pressure medications
CoQ10 may lower BP modestly.
What to do: Monitor BP. May allow dose reduction of BP meds under doctor supervision.
Source: Clinical consensus
Chemotherapy
CoQ10 is an antioxidant. Theoretical concern about protecting cancer cells.
What to do: Discuss with your oncologist before using during active treatment.
Source: Theoretical
Insulin and diabetes medications
CoQ10 may improve insulin sensitivity.
What to do: Monitor blood sugar.
Source: Clinical consensus
Dangerous (2)
Warfarin and other anticoagulants
Ginkgo inhibits platelet-activating factor (PAF).
What to do: Avoid combination. Stop ginkgo 2 weeks before surgery.
Source: FDA MedWatch reports
Aspirin and NSAIDs
Additive antiplatelet effect.
What to do: Avoid combination.
Source: Clinical pharmacology
Moderate (2)
Seizure medications (valproate, phenytoin)
Ginkgo may lower seizure threshold.
What to do: Avoid in epilepsy patients.
Source: Case reports
CYP2C9 substrates
Ginkgo may induce CYP2C9.
What to do: Monitor.
Source: In vitro data
Moderate (5)
Warfarin and other anticoagulants
Melatonin may enhance anticoagulant effect.
What to do: Monitor INR.
Source: Case reports
Immunosuppressants
Melatonin stimulates immune function.
What to do: Avoid in transplant patients.
Source: Clinical pharmacology
Diabetes medications
Melatonin may affect glucose metabolism.
What to do: Monitor glucose.
Source: Clinical consensus
Sedatives and benzodiazepines
Additive CNS depression.
What to do: Use lower doses of both.
Source: Clinical consensus
Fluvoxamine (Luvox)
Fluvoxamine inhibits CYP1A2, dramatically increasing melatonin levels.
What to do: Reduce melatonin dose to 0.5mg or avoid.
Source: Clinical pharmacology
Moderate (3)
Nitroglycerin
NAC potentiates nitric oxide vasodilation.
What to do: Avoid combination or use with extreme caution.
Source: Clinical pharmacology
Activated charcoal
Charcoal adsorbs NAC, reducing efficacy.
What to do: Separate by 1 to 2 hours.
Source: Emergency medicine standard
Anticoagulants
NAC has mild antiplatelet properties.
What to do: Low clinical significance. Monitor.
Source: Clinical consensus
Moderate (5)
Nadolol (beta-blocker)
Green tea catechins reduce nadolol absorption via OATP inhibition.
What to do: Separate by 4 or more hours, or avoid.
Source: Clinical study
Warfarin
Small vitamin K content plus catechin antiplatelet effect.
What to do: Keep intake consistent. Monitor INR.
Source: Clinical consensus
Iron supplements
Tannins in green tea chelate iron.
What to do: Separate by 2 or more hours.
Source: Clinical standard
Stimulant medications (Adderall, Ritalin)
Caffeine in green tea is additive.
What to do: Limit green tea on stimulant days.
Source: Clinical consensus
MAOIs
Caffeine plus tyramine interaction possible.
What to do: Avoid high-caffeine green tea extracts on MAOIs.
Source: Clinical pharmacology
Moderate (4)
Thiazide diuretics (HCTZ)
Thiazides reduce calcium excretion while vitamin D increases calcium absorption.
What to do: Monitor serum calcium.
Source: Clinical standard
Steroids (prednisone)
Corticosteroids reduce vitamin D metabolism and calcium absorption.
What to do: Higher vitamin D doses may be needed on long-term steroids.
Source: Clinical standard
Orlistat (Alli)
Reduces fat absorption, including fat-soluble vitamin D.
What to do: Separate by 2 or more hours. Monitor 25-OH vitamin D.
Source: FDA label
Cholestyramine (bile acid sequestrant)
Reduces vitamin D absorption.
What to do: Separate by 4 or more hours.
Source: FDA label
Moderate (2)
Levodopa (without carbidopa)
B6 increases peripheral conversion of levodopa to dopamine.
What to do: Avoid B6 over 10mg/day with levodopa alone. Safe with levodopa/carbidopa combinations (Sinemet).
Source: FDA label
Phenytoin (Dilantin)
High-dose B6 may increase phenytoin metabolism.
What to do: Avoid B6 over 200mg/day with phenytoin.
Source: Clinical pharmacology
Moderate (3)
Methotrexate
Folic acid competes with methotrexate for folate receptors.
What to do: In cancer, avoid folic acid. In rheumatoid arthritis, use leucovorin or folinic acid prescribed by your rheumatologist.
Source: FDA label
Phenytoin (Dilantin)
Folic acid may reduce phenytoin levels.
What to do: Monitor phenytoin levels when starting folic acid.
Source: Clinical pharmacology
5-Fluorouracil (5-FU)
Folic acid (as leucovorin) is sometimes given with 5-FU to enhance its effect.
What to do: Only under oncologist supervision.
Source: Oncology standard
Moderate (4)
Warfarin and other anticoagulants
Garlic has antiplatelet properties (ajoene inhibits platelet aggregation).
What to do: Monitor INR. Avoid high-dose garlic supplements on warfarin.
Source: Clinical pharmacology
HIV protease inhibitors (saquinavir)
Garlic may induce CYP3A4, reducing drug levels.
What to do: Avoid combination.
Source: Clinical study (saquinavir levels reduced 51%)
Isoniazid (TB treatment)
Garlic may reduce isoniazid absorption.
What to do: Separate dosing.
Source: Limited evidence
Blood pressure medications
Additive BP-lowering effect.
What to do: Monitor BP. Usually beneficial.
Source: Clinical consensus
Informational only. Always consult your pharmacist or physician before combining supplements with medications.