Interactions
Before the remedy: check your medicines
Food can change how a medicine works. These 20 interactions are drawn from NIH Office of Dietary Supplements and NCCIH fact sheets, FDA guidance and published studies, each graded by how well it is documented in people. This list is not complete: your pharmacist can check everything you take.
- Established in drug labeling or controlled human studies
- Probable case reports plus a known mechanism
- Theoretical mechanism or lab data only
Showing 20 of 20 interactions.
- Aged, fermented and cured foods high in tyramine and MAO inhibitor antidepressants, such as phenelzine (Nardil)EstablishedEating high-tyramine foods while taking an MAO inhibitor can cause a sudden, dangerous rise in blood pressure, sometimes called the cheese reaction.What to do
- Black licorice and licorice root (glycyrrhizin) and blood pressure medicines and diuretics (water pills)EstablishedRegular licorice raises blood pressure and lowers potassium, working against blood pressure treatment. Reviews of interaction reports include low potassium after licorice combined with antihypertensives.What to do
- Black licorice and licorice root (glycyrrhizin) and digoxin (Lanoxin)TheoreticalLicorice can lower blood potassium, and low potassium makes digoxin toxicity more likely. The combination could raise the risk of dangerous heart rhythm problems.What to do
- Chamomile tea and chamomile products and warfarinProbableA published case described a 70-year-old woman on warfarin admitted with multiple internal bleeds after using chamomile tea and lotion. NCCIH notes reported interactions between chamomile and warfarin and some drugs metabolized by the liver.What to do
- Coffee, soy, walnuts and high-fiber foods and levothyroxine (Synthroid, Levoxyl, others)EstablishedTaking levothyroxine with coffee lowered its absorption in a small controlled study (absorption measures fell by roughly 20 to 36 percent), and bran fiber interfered even more. MedlinePlus warns that soybeans, walnuts and dietary fiber may affect how levothyroxine works.What to do
- Cranberry juice and cranberry supplements and warfarinProbableCase reports linked cranberry with raised INR and bleeding, but a randomized double-blind trial of 240 mL of cranberry juice a day for two weeks found no change in warfarin levels and no clinically important change in INR. NCCIH calls the evidence conflicting.What to do
- Echinacea and immunosuppressants, such as cyclosporine after a transplantTheoreticalEchinacea is thought to stimulate parts of the immune system, which could work against drugs meant to suppress it. Its effects on cyclosporine levels have not been shown consistently.What to do
- Enteric-coated peppermint oil capsules and antacids and acid reducers (H2 blockers, proton pump inhibitors)TheoreticalAcid reducers may cause enteric-coated peppermint oil capsules to open in the stomach instead of the intestine, raising the chance of heartburn.What to do
- Fish oil and omega-3 supplements and warfarin and other anticoagulantsProbableHigh doses of omega-3s may add to bleeding tendency with anticoagulants, though a small randomized trial of 3 to 6 g of fish oil a day found no significant change in INR in people on stable warfarin.What to do
- Garlic supplements and saquinavir, an HIV protease inhibitorEstablishedIn a controlled NIH study in 10 healthy volunteers, three weeks of garlic caplets cut saquinavir blood levels by about half, and levels had not fully recovered 10 days after stopping garlic.What to do
- Garlic supplements and warfarin and other anticoagulants, aspirin and antiplatelet drugsProbableGarlic supplements may increase the risk of bleeding, which matters when combined with drugs that also affect bleeding or before surgery. In a small trial, aged garlic extract did not increase bleeding in closely monitored warfarin patients.What to do
- Ginger supplements and warfarin and other blood thinnersProbableThe evidence is mixed. A controlled study in healthy volunteers found ginger at recommended doses did not change warfarin levels or clotting, but a 2021 systematic review listed ginger among foods and herbs linked with bleeding risk on warfarin, based mostly on case reports.What to do
- Grapefruit and grapefruit juice and some statins, such as simvastatin (Zocor) and atorvastatin (Lipitor)EstablishedGrapefruit can let more of the statin into the bloodstream. FDA warns that with a lot of grapefruit juice, too much of some statins may stay in the body, raising the risk of muscle and liver damage.What to do
- Grapefruit and grapefruit juice and some calcium channel blockers for blood pressure, such as felodipine and nifedipineEstablishedIn the 1991 study that first described the interaction, felodipine taken with grapefruit juice reached on average 284% of the blood level reached with water, with lower blood pressure, a faster heart rate and more side effects. Orange juice had no such effect.What to do
- Green tea and nadolol (Corgard), a beta-blockerEstablishedIn healthy volunteers who drank green tea daily for two weeks, nadolol blood levels fell by about 85% and its effect on systolic blood pressure was significantly reduced.What to do
- Leafy greens and other vitamin K-rich foods and warfarin (Coumadin, Jantoven)EstablishedVitamin K works against warfarin. A sudden rise in vitamin K intake can make warfarin less effective, and a sudden drop can push the INR up.What to do
- Milk, yogurt, cheese and calcium-fortified juice and tetracycline antibiotics and fluoroquinolones such as ciprofloxacinEstablishedCalcium binds these antibiotics in the gut, so less of the drug is absorbed and the infection may be treated less well.What to do
- Potassium-rich foods and potassium salt substitutes and ACE inhibitors (such as lisinopril), ARBs and potassium-sparing diureticsEstablishedThese medicines reduce how much potassium the kidneys get rid of. Adding potassium supplements or potassium-based salt substitutes can push blood potassium too high, especially with kidney disease.What to do
- Psyllium husk and other oral medicines, especially digoxin, aspirin and nitrofurantoinEstablishedPsyllium can bind or slow the absorption of other medicines taken at the same time.What to do
- Turmeric and curcumin supplements and warfarin, clopidogrel and other blood thinnersTheoreticalTurmeric supplements are often said to add to bleeding risk with blood thinners. The evidence is thin: in a rat study curcumin changed warfarin and clopidogrel levels without changing clotting, and good human data are lacking.What to do