Supplement Interactions Database 2026
82 verified interactions between supplements and between supplements and prescription drugs. Every entry cites a primary source. No AI-generated warnings, no marketing claims.
82Interactions
3Severe cautions
20Drug interactions
10Documented synergies
Not medical advice. This database is a starting point for discussions with a physician or pharmacist. Individual response varies. Blood-thinning, immunosuppressive, and CYP-metabolized drugs need clinical oversight. When in doubt, stop the supplement and consult a professional.
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Severe caution
Drug interaction
Moderate caution
Synergy
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82 of 82 interactions shown
Mechanism. Cyclosporine raises sirolimus exposure through CYP3A4 and P-glycoprotein. The label directs sirolimus to be given 4 hours after cyclosporine.
Consequence. Excess immunosuppression and toxicity if timing or blood levels are not controlled. Therapeutic drug monitoring is required.
Recommendation. Ask a physician before combining [1]
Mechanism. Sirolimus is a CYP3A4 and P-glycoprotein substrate. Strong inhibitors such as ketoconazole, itraconazole, clarithromycin and erythromycin raise its blood levels, and grapefruit juice is contraindicated.
Consequence. Sirolimus concentrations climb and toxicity risk rises. The label says to avoid strong inhibitors and inducers.
Recommendation. Avoid this combination [1]
Mechanism. Curcumin has antiplatelet and NSAID-like activity that adds to warfarin. Medsafe reported a patient with stable INR whose INR rose above 10 within weeks of starting a turmeric product.
Consequence. Serious bleeding risk. The warning covers concentrated supplements, not turmeric used as a spice.
Recommendation. Avoid this combination [1]
Mechanism. Ashwagandha lowers TSH and raises T3 and T4. A 73-year-old woman on ashwagandha developed thyrotoxicosis with a heart rate of 173 bpm and TSH below 0.01 mcIU/mL, which resolved after stopping.
Consequence. Over-replacement with palpitations, tremor and heat intolerance. Thyroid labs need checking if ashwagandha is used.
Mechanism. Rhodiola has monoamine oxidase inhibiting activity and raises serotonin and dopamine turnover. A 68-year-old woman on paroxetine developed restlessness and tremor after adding rhodiola.
Consequence. Serotonergic symptoms and, in one MSK-reported case, tachyarrhythmia after 3 days of use.
Mechanism. Garlic induces P-glycoprotein and alters CYP activity, lowering exposure to immunosuppressants and protease inhibitors. In volunteers, garlic cut protease inhibitor peak levels by 54%.
Consequence. Loss of drug effect, with reported transplant rejection risk and HIV viral rebound.
Recommendation. Avoid this combination [1]
Mechanism. Ginkgo reduces platelet aggregation and adds to warfarin's effect. In 807,399 warfarin patients in the VA system, bleeding occurred in 22.6% of ginkgo users versus 18.0% of non-users, adjusted hazard ratio 1.38 to 2.08.
Consequence. Higher risk of bruising, nosebleeds and serious bleeds. Case reports include intracerebral hemorrhage.
Mechanism. High-dose vitamin E antagonizes vitamin K. In healthy adults, 1,000 IU per day for 12 weeks reduced gamma-carboxylation of prothrombin.
Consequence. Bleeding risk rises with anticoagulants, clopidogrel, aspirin and NSAIDs. A case report describes coagulopathy after 400 mg twice daily for 2 months.
Mechanism. Iron salts form insoluble complexes with levothyroxine in the gut. Ferrous sulfate raised mean TSH from 1.6 to 5.4 mU/L in 11 of 14 treated patients.
Consequence. Thyroid dose stops working and TSH climbs. Separating the doses restores absorption.
Mechanism. Coffee taken with levothyroxine tablets cut the incremental serum T4 rise by 29% to 36% and delayed peak by 38 to 43 minutes.
Consequence. Under-replacement and rising TSH if the tablet is always taken with coffee. Water first, coffee an hour later, keeps absorption intact.
Mechanism. Glucosamine, alone or with chondroitin, potentiates warfarin by an unclear pharmacodynamic route. Animal work shows inhibited platelet aggregation and thromboxane A2 production.
Consequence. INR rises, sometimes sharply. In one case INR went from 2.3 to 4.7; 21 of 22 WHO reports showed increased warfarin effect and 4 needed vitamin K.
Mechanism. In a randomized controlled trial in 20 healthy adults, 2 weeks of American ginseng lowered peak INR by 0.19 and reduced peak plasma warfarin and warfarin AUC.
Consequence. Warfarin becomes less effective, so clot risk rises. MSK also notes mixed reports of increased bleeding risk.
Mechanism. Methylene blue is a potent reversible MAO-A inhibitor, inhibition constant 27 nM. Combined with an SSRI it can trigger serotonin syndrome.
Consequence. Agitation, tremor, hyperthermia and rigidity. The FDA label says to avoid concomitant serotonergic drugs and to allow 72 hours after the last dose.
Mechanism. Green tea catechins inhibit the OATP1A2 uptake transporter. In 10 healthy volunteers, green tea cut nadolol peak concentration by 85.3% and exposure by 85.0%.
Consequence. The beta blocker stops lowering blood pressure properly. Effect was seen with 700 mL green tea daily for 14 days.
Mechanism. ACE inhibitors reduce aldosterone and cut renal potassium excretion. Added potassium pushes serum potassium higher.
Consequence. Hyperkalemia, worse with chronic kidney disease, heart failure, NSAIDs or potassium-sparing diuretics. Potassium and creatinine need checking 7 to 14 days after any change.
Recommendation. Ask a physician before combining [1]
Mechanism. ARBs block the AT1 receptor and raise serum potassium the same way ACE inhibitors do.
Consequence. Hyperkalemia risk. Risk is highest with combined renin-angiotensin blockade, mineralocorticoid antagonists or reduced kidney function.
Recommendation. Ask a physician before combining [1]
Mechanism. Resveratrol inhibits CYP3A4 by direct and mechanism-based inactivation. In humans, 500 mg/day for 10 days raised carbamazepine AUC 1.5-fold.
Consequence. Higher anticonvulsant levels with sedation, ataxia or nausea. Dose adjustment needs medical input.
Mechanism. In healthy volunteers, 1 g/day resveratrol for 4 weeks inhibited CYP3A4, CYP2D6 and CYP2C9 and changed buspirone AUC by 33%.
Consequence. Clearance of many prescription drugs falls, so their levels and side effects rise. The review advises against supplementation in people taking CYP3A4 substrates.
Mechanism. Warfarin works by blocking vitamin K recycling. Supplemental vitamin K2 restores clotting factor carboxylation and pushes INR down.
Consequence. INR falls and clot risk rises. Stopping the supplement later swings INR the other way.
Recommendation. Ask a physician before combining [1]
Mechanism. Metformin reduces intestinal vitamin B12 absorption. A meta-analysis of 29 studies with 8,089 patients found odds of B12 deficiency of 2.45 and mean serum B12 lower by 65.8 pmol/L.
Consequence. Long-term metformin users can develop low B12 with fatigue, numbness or anemia. B12 supplementation corrects the gap.
Mechanism. Berberine lowers fasting and postprandial glucose on its own, with 500 mg three times daily cutting HbA1c from 9.47% to 7.48% in newly diagnosed type 2 diabetes.
Consequence. Hypoglycemia risk when stacked on insulin or sulfonylureas. Glucose starts dropping in the first week.
Mechanism. Rhodiola shows monoamine oxidase inhibiting activity, which overlaps with MAO inhibitor drugs.
Consequence. Hypertensive or serotonergic reactions are plausible. MSK also flags hypertension when rhodiola is combined with CNS stimulants.
Recommendation. Avoid this combination [1]
Mechanism. Rhodiola causes modest CYP2C9 inhibition, the enzyme that clears phenytoin and warfarin. Preclinical work also suggests CYP3A4 and P-glycoprotein inhibition.
Consequence. Anticonvulsant or anticoagulant levels can drift upward. Clinical relevance is undetermined.
Recommendation. Ask a physician before combining [1]
Mechanism. Resveratrol inhibits platelet aggregation in vitro and reduced CYP2C9 activity 2.71-fold at 1 g/day for 4 weeks. CYP2C9 clears the active warfarin enantiomer.
Consequence. Higher bleeding risk and unstable INR. MSK advises discussing use with the treating physician.
Mechanism. Curcuminoids inhibit CYP3A, and sirolimus is a CYP3A4 and P-glycoprotein substrate whose label warns against CYP3A4 inhibitors and grapefruit juice.
Consequence. Sirolimus blood levels can rise. Anyone on sirolimus needs level monitoring before adding curcumin.
Mechanism. Fisetin and its methylated metabolite geraldol selectively inhibit CYP2C8 in human liver microsomes.
Consequence. Possible higher levels of CYP2C8 substrate drugs. No human pharmacokinetic data exist.
Recommendation. Ask a physician before combining [1]
Mechanism. Vitamin D and some statins compete for the same metabolizing enzyme, and statins may reduce endogenous vitamin D synthesis.
Consequence. High vitamin D intake might reduce the potency of atorvastatin, lovastatin and simvastatin.
Recommendation. OK to combine [1]
Mechanism. Ginkgo may affect insulin secretion and blood glucose.
Consequence. Unpredictable glucose readings in people on insulin or other glucose-lowering drugs. MSK advises consulting a healthcare provider.
Recommendation. Ask a physician before combining [1]
Mechanism. Ginsenosides have stimulatory central nervous system effects that can compound MAO inhibition.
Consequence. Manic-like symptoms have been reported with MAO inhibitors, and one case linked 250 mg three times daily to mania.
Recommendation. Avoid this combination [1]
Mechanism. Asian ginseng may induce CYP3A4 and increase clearance of CYP3A4 substrate drugs, although human effects may not be clinically significant.
Consequence. Substrate drug levels can fall. MSK also advises stopping ginseng at least 1 week before surgery.
Recommendation. Ask a physician before combining [1]
Mechanism. Garlic increases fibrinolytic activity and reduces platelet aggregation, which can enhance warfarin. Garlic is also linked to surgical bleeding independent of anticoagulants.
Consequence. Elevated INR and bleeding reports. MSK advises stopping garlic supplements at least 7 days before surgery.
Mechanism. CoQ10 is structurally similar to vitamin K and may antagonize warfarin. A 72-year-old woman became less warfarin-responsive on CoQ10 and returned to baseline after stopping.
Consequence. INR can drift down, raising clot risk. Some reports describe the opposite, increased bleeding risk.
Mechanism. Quercetin inhibits CYP3A4 and CYP2C19 in vitro, pathways relevant to warfarin metabolism.
Consequence. A 79-year-old man on stable warfarin had an elevated INR on quercetin that normalized after stopping.
Recommendation. Ask a physician before combining [1]
Mechanism. Quercetin inhibits CYP3A4 with an IC50 of 1.97 micromolar and blocks P-glycoprotein efflux. In rats it raised oral doxorubicin AUC by 31% to 136%.
Consequence. Higher plasma levels of CYP3A4 or P-glycoprotein substrate drugs. Human relevance is not established.
Mechanism. Curcuminoids inhibit CYP3A with a Ki of 11.0 micromolar and also inhibit CYP2C9, CYP2C19, UGT and SULT enzymes.
Consequence. Drug clearance can fall, especially with piperine-enhanced products. Watch for stronger drug effects.
Recommendation. Ask a physician before combining [1]
Mechanism. Berberine plus a statin inhibits CYP3A4 more than berberine alone and further reduces hERG potassium channel current in laboratory models.
Consequence. Theoretical QT prolongation and higher statin levels with muscle symptoms. Data are preclinical.
Recommendation. Ask a physician before combining [1]
Mechanism. Berberine alters sirolimus pharmacokinetics through CYP3A4. Repeated berberine dosing in rats raised sirolimus Cmax from 5.55 to 7.86 ng/mL and AUC by 38%.
Consequence. Sirolimus levels can shift in either direction depending on dosing pattern. Blood level monitoring is needed.
Mechanism. Chromium supplements reduce levothyroxine absorption in the gut, in the same way as calcium and iron.
Consequence. Lower thyroid hormone exposure. The systematic review recommends separating chromium from levothyroxine by 3 to 4 hours.
Recommendation. Space by 2 hours [1]
Mechanism. Calcium adsorbs levothyroxine at acidic pH. Calcium carbonate 1,200 mg/day cut levothyroxine absorption from 83.7% to 53.7% and raised mean TSH from 1.6 to 2.7 mIU/L, with 20% of patients above the normal TSH range.
Consequence. Any calcium-containing supplement, including calcium alpha-ketoglutarate, can blunt the thyroid dose if taken at the same time.
Mechanism. Calcium inhibits both heme and nonheme iron absorption when both are in the upper small intestine at the same time. The effect is dose-dependent.
Consequence. Lower iron uptake from a single dose. Long-term iron status is usually unaffected, but separating the doses is simple insurance.
Mechanism. Tea catechols bind iron in the gut and inhibit heme and nonheme iron absorption in a dose-dependent way.
Consequence. A man drinking over 1,500 mL green tea daily for 20 years developed iron deficiency anemia with hemoglobin 6.2 g/dL and ferritin 1.6 ng/mL.
Recommendation. Space by 2 hours [1]
Mechanism. Green tea extract inhibits uptake transporters and reduced exposure to rosuvastatin, raloxifene and nintedanib, the last by 21%.
Consequence. The statin may work less well. Separating doses limits transporter competition.
Recommendation. Space by 2 hours [1]
Mechanism. Chondroitin is usually taken with glucosamine, and the combination is linked to increased INR. Reviews group chondroitin-glucosamine with supplements associated with anticoagulant-related bleeding.
Consequence. INR can rise weeks after starting or increasing the dose.
Mechanism. High folic acid intake can correct the anemia of B12 deficiency while nerve damage continues, and is linked to lower holotranscobalamin.
Consequence. Low B12 goes undetected. People with low B12 and high folate show worse cognitive scores and higher homocysteine and methylmalonic acid.
Mechanism. Thiazide diuretics cut urinary calcium excretion while vitamin D increases intestinal calcium absorption.
Consequence. Hypercalcemia, mainly in older adults or people with reduced kidney function or hyperparathyroidism.
Recommendation. Ask a physician before combining [1]
Mechanism. Gut bacteria convert both L-carnitine and free choline to trimethylamine, which the liver oxidizes to TMAO. Choline bitartrate 1,000 mg/day raised fasting TMAO from 1.9 to 11.1 micromolar in 4 weeks and increased platelet responsiveness.
Consequence. Stacking both pushes TMAO higher than either alone. Eggs and phosphatidylcholine capsules did not raise TMAO in the same trial.
Mechanism. EPA and DHA displace arachidonic acid in platelet membranes and reduce thromboxane A2. In 573 warfarin patients, fish or krill oil users had the same time in therapeutic range as controls, 86.7% versus 86.9%.
Consequence. No measurable INR shift at common doses. Bleeding risk concerns apply mainly above 3 g EPA plus DHA daily.
Mechanism. Omega-3 has mild antiplatelet activity that overlaps with aspirin and clopidogrel. A review including a fish oil RCT with 25,871 participants found no association with increased bleeding.
Consequence. Minor bruising or nosebleeds are possible. Report any unusual bleeding before surgery or procedures.
Recommendation. OK to combine [1]
Mechanism. Korean red ginseng at 6 g/day for 12 weeks lowered 75 g OGTT glucose indices by 8% to 11% and raised insulin sensitivity indices by 33% in well-controlled type 2 diabetes.
Consequence. Added glucose lowering on top of insulin or sulfonylureas can cause hypoglycemia.
Mechanism. A meta-analysis of 41 studies found alpha-lipoic acid reduced fasting blood glucose by 6.57 mg/dL and HbA1c by 0.35%.
Consequence. Glucose can run lower than expected with insulin or sulfonylureas. Monitor readings when starting.
Recommendation. Ask a physician before combining [1]
Mechanism. Taurine 1.6 g/day for 12 weeks lowered clinic blood pressure by 7.2/2.6 mmHg versus placebo in 120 prehypertensive adults, partly through increased hydrogen sulfide.
Consequence. Additive blood pressure reduction with antihypertensive drugs. Watch for lightheadedness.
Recommendation. OK to combine [1]
Mechanism. NAC donates sulfhydryl groups that potentiate nitrate-induced vasodilation. In 11 volunteers, NAC raised median nitroglycerin headache score from 1 to 3 and temporal artery dilation from 127% to 139% of baseline.
Consequence. Severe headache and more pronounced hypotension after nitrate dosing.
Recommendation. Ask a physician before combining [1]
Mechanism. Zinc and iron compete for the same intestinal uptake route. At zinc to iron molar ratios of 5:1 and above, iron absorption fell 28% to 40% in 22 women. Iron doses of 25 mg or more also cut zinc absorption.
Consequence. Taking both together in one dose blunts absorption of each. Splitting the doses avoids the problem.
Mechanism. A systematic review of 10 studies found creatine loading does not blunt an acute caffeine dose, but chronic caffeine during creatine loading interfered with creatine's benefit in 2 studies.
Consequence. Possible loss of creatine loading benefit and more gastrointestinal upset. Results across studies are mixed.
Recommendation. OK to combine [1]
Mechanism. Both activate AMPK and lower glucose. In a meta-analysis of 50 RCTs with 4,150 participants, berberine added to glucose-lowering drugs reduced fasting glucose by 0.99 mmol/L and HbA1c by 0.69%.
Consequence. Additive glucose lowering plus more gastrointestinal upset. Gastrointestinal side effects hit 34.5% of patients in one combination trial.
Mechanism. Magnesium lowers blood pressure by roughly 2.0 mmHg systolic and 1.8 mmHg diastolic across 34 double-blind trials with 2,028 adults, median 368 mg/day.
Consequence. Small additive drop in blood pressure on top of antihypertensive drugs. Watch for dizziness on standing.
Mechanism. Both are NAD+ precursors feeding the same salvage pathway. NMN is dephosphorylated extracellularly to NR before cellular uptake, and both can be degraded to nicotinamide by the liver or gut microbiome.
Consequence. Running both raises cost without a demonstrated extra rise in NAD+. Pick one and dose it properly.
Recommendation. OK to combine [1]
Mechanism. Both products deliver elemental magnesium through the same absorption route. Only the counter-ion and the laxative effect differ.
Consequence. Combined elemental magnesium can pass the 350 mg/day supplemental upper level and cause diarrhea and cramping.
Recommendation. Reduce dose [1]
Mechanism. Magnesium L-threonate is one more elemental magnesium source. Total elemental magnesium is what counts against the tolerable upper intake level.
Consequence. Stacking forms adds up quickly. Loose stools are the first sign of too much.
Recommendation. Reduce dose [1]
Mechanism. Two organic magnesium salts with the same elemental payload and the same dose-limiting gastrointestinal effect.
Consequence. No added benefit from running both. Count total elemental magnesium instead.
Recommendation. Reduce dose [1]
Mechanism. Both are marketed for stress and both act on stress-response signaling, ashwagandha through the HPA axis and GABAergic pathways, rhodiola through monoamine turnover and MAO inhibition.
Consequence. Overlapping effects with additive sedation from ashwagandha or overstimulation from rhodiola. No trial shows benefit from combining them.
Mechanism. The senolytic protocol already delivers quercetin 1,000 mg daily for 3 days alongside dasatinib.
Consequence. Extra standalone quercetin on protocol days adds dose without a defined target. Keep to the studied amount.
Recommendation. Reduce dose [1]
Mechanism. Both products deliver choline. Six 420 mg phosphatidylcholine capsules supply about 410 mg choline, close to two 500 mg choline bitartrate tablets.
Consequence. Doubling up adds intake without new function. Free choline raised TMAO in trial participants while phosphatidylcholine did not.
Recommendation. OK to combine [1]
Mechanism. Oral glutathione is largely broken down by intestinal gamma-glutamyl transpeptidase. NAC instead supplies cysteine for glutathione synthesis inside cells.
Consequence. Stacking oral glutathione on NAC adds cost without a clear extra benefit. In a crossover study only sublingual glutathione raised plasma glutathione.
Recommendation. OK to combine [1]
Mechanism. Every enzyme that metabolizes vitamin D appears to need magnesium as a cofactor in the liver and kidney.
Consequence. Low magnesium status limits the benefit of vitamin D dosing.
Recommendation. OK to combine [1]
Mechanism. Iodine needs peroxidase enzymes and hydrogen peroxide for thyroid hormone synthesis, while selenoproteins detoxify that peroxide and run the deiodinases that make T3.
Consequence. High iodine appears better tolerated when selenium status is adequate. Iodate above 50 mg/day for 8 weeks raised TSH in 10 of 43 older adults.
Mechanism. Glycine and cysteine are the rate-limiting substrates for glutathione synthesis. In a randomized trial, 16 weeks of combined glycine plus NAC corrected glutathione deficiency, oxidative stress and mitochondrial dysfunction in older adults.
Consequence. Higher glutathione and better physical function markers than either compound alone.
Recommendation. OK to combine [1]
Mechanism. Piperine inhibits intestinal and hepatic glucuronidation of curcumin. In human volunteers, 20 mg piperine with 2 g curcumin raised curcumin bioavailability by 2000%.
Consequence. Much higher blood curcumin from the same dose. The same enzyme inhibition also raises drug interaction risk.
Mechanism. Insulin drives creatine into muscle. Taking 93 g simple carbohydrate 30 minutes after each 5 g creatine dose raised muscle total creatine 60% more than creatine alone over 5 days.
Consequence. Faster muscle saturation during loading. A later trial found no extra performance gain from the added carbohydrate.
Mechanism. Dasatinib and quercetin disable complementary senescent cell anti-apoptotic pathways. Dasatinib hits senescent adipocyte progenitors, quercetin hits senescent endothelial cells.
Consequence. In 9 adults, 3 days of dasatinib 100 mg plus quercetin 1,000 mg daily reduced adipose senescent cell markers by 17% to 62%. Dasatinib is a prescription cancer drug and needs medical supervision.
Recommendation. Ask a physician before combining [1]
Mechanism. Vitamin D raises production of osteocalcin and matrix Gla protein, which only work after vitamin K-dependent carboxylation.
Consequence. Without enough vitamin K these proteins stay uncarboxylated. Combined low vitamin K and low 25(OH)D carried hip fracture odds of 7.6 in one cohort.
Recommendation. OK to combine [1]
Mechanism. Statins lower circulating CoQ10 by 16% to 54%. A meta-analysis of 12 RCTs with 575 patients found CoQ10 reduced statin-linked muscle pain, weakness, cramps and fatigue.
Consequence. Muscle symptoms often improve. Creatine kinase does not change, so CoQ10 does not treat true statin myopathy.
Mechanism. In two randomized crossover trials, 40-50 mg caffeine with 97-100 mg L-theanine improved attention-switching speed and accuracy and cut susceptibility to distraction.
Consequence. Better focus at 60-90 minutes with less of the jittery feeling from caffeine alone.
Mechanism. Ascorbic acid reduces ferric to ferrous iron and keeps it soluble. A systematic review and meta-analysis found nonheme iron absorption rose by 5.87 percentage points and hemoglobin by 8.26 g/L with longer supplementation.
Consequence. More iron absorbed per dose. People with hemochromatosis or other iron overload should not use high-dose vitamin C with iron.