Allopurinol is used to treat gout. Taking large doses of niacin might worsen gout and decrease the effects of allopurinol.

Gemfibrozil

• Lopid

Taking niacin along with gemfibrozil might increase the risk for muscle damage in some people. Use with caution.

Medications for diabetes

• Glyburide

• Glipizide

• Insulin

• Sitagliptin

• Empagliflozin

• Semaglutide

• Dapagliflozin

High doses of niacin might increase blood sugar levels. Taking niacin along with diabetes medications might reduce the effects of these medications. Monitor your blood sugar closely.

Medications for high blood pressure

• Amlodipine

• Ramipril

• Perindopril

• Metoprolol

• Losartan

• Hydrochlorothiazide

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

Medications that can harm the liver

• Acetaminophen / Paracetamol

• Methotrexate

• Atorvastatin

• Simvastatin

• Isoniazid

Niacin might harm the liver. Some medications can also harm the liver. Taking niacin along with a medication that can harm the liver might increase the risk of liver damage.

Medications that slow blood clotting

• Heparin

• Rivaroxaban

• Apixaban

• Dabigatran

• Clopidogrel

Niacin might slow blood clotting. Taking niacin along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

Medications used for lowering cholesterol

• Bile acid sequestrants

Some medications called bile acid sequestrants can decrease how much niacin the body absorbs. This might reduce the effects of niacin. Take niacin and these medications at least 4-6 hours apart.

• Atorvastatin

• Rosuvastatin

• Simvastatin

• Pravastatin

• Fluvastatin

Taking niacin along with statins might increase the risk for muscle damage in some people. Use with caution.

Nicotine patch

• Nicoderm

Niacin can sometimes cause flushing and dizziness. Nicotine patches can also cause flushing and dizziness. Taking niacin and using a nicotine patch may increase the risk of flushing and dizziness.

Probenecid

• Benemid

Probenecid is used to treat gout. Taking large doses of niacin might worsen gout and decrease the effects of probenecid.

Sulfinpyrazone

• Anturane

Sulfinpyrazone is used to treat gout. Taking large doses of niacin might worsen gout and decrease the effects of sulfinpyrazone.

Thyroid hormone

The body naturally produces thyroid hormones. Niacin might decrease thyroid hormone levels. Taking niacin with thyroid hormone pills might decrease the effects of thyroid hormone.

• Jantoven

• Used for: blood thinning, clot prevention

Niacin might increase the blood thinning effects of warfarin and potentially increase the chance of bleeding. Your healthcare provider may need to monitor you more often if you take niacin along with warfarin. The dose of your warfarin medication may need to be changed.

Aluminum

Aluminum is found in most antacids. Vitamin C can increase how much aluminum the body absorbs. However, it is not clear if this interaction is a big concern. Take vitamin C two hours before or four hours after antacids.

Estrogens

• Oral contraceptive pill

• Estradiol

• Conjugated estrogens

• HRT combination products

Vitamin C might decrease how quickly the body gets rid of estrogens. Taking vitamin C along with estrogens might increase the effects and side effects of estrogens.

Fluphenazine

• Prolixin

Large amounts of vitamin C might decrease how much fluphenazine is in the body. Taking vitamin C along with fluphenazine might decrease the effectiveness of fluphenazine.

Indinavir

• Crixivan

Taking large amounts of vitamin C along with indinavir might decrease how much indinavir stays in the body. It's not clear if this interaction is a big concern.

Levothyroxine

• Synthroid, others

Taking vitamin C along with levothyroxine might increase how much levothyroxine the body absorbs. This can increase the amount of levothyroxine in the body and increase its effects and side effects.

Medications for cancer

• Cyclophosphamide

• Chlorambucil

• Melphalan

• Busulfan

• Temozolomide

Vitamin C is an antioxidant. There is some concern that antioxidants might decrease the effects of some medications used for cancer. If you are taking medications for cancer, check with your healthcare provider before taking vitamin C.

• Doxorubicin

• Bleomycin

• Daunorubicin

• Mitomycin

• Epirubicin

Vitamin C is an antioxidant. There is some concern that antioxidants might decrease the effects of medications used for cancer. If you are taking medications for cancer, check with your healthcare provider before taking vitamin C.

Niacin

Taking niacin with vitamin C and other antioxidants can decrease the effects of niacin on good cholesterol levels. It is unknown if vitamin C alone decreases the effects of niacin on good cholesterol levels.

Warfarin is used to slow blood clotting. Large amounts of vitamin C might decrease the effects of warfarin. Decreasing the effects of warfarin might increase the risk of clotting. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.

Atorvastatin

Vitamin D might decrease how much atorvastatin the body absorbs. Taking vitamin D with atorvastatin might decrease the effects of atorvastatin.

Calcipotriene

• Dovonex

Taking vitamin D along with calcipotriene might increase the effects and side effects of calcipotriene.

• Used for: heart failure, atrial fibrillation

Taking vitamin D along with digoxin might increase the effects and side effects of digoxin. If you are taking digoxin, talk to your doctor before taking vitamin D supplements.

Diltiazem

• Cardizem, others

Vitamin D helps your body absorb calcium. Calcium can affect the heart. Diltiazem can also affect the heart. Taking large amounts of vitamin D along with diltiazem might decrease the effects of diltiazem.

Verapamil

• Calan, others

Vitamin D helps the body absorb calcium. Calcium can affect the heart. Verapamil can also affect the heart. Do not take large amounts of vitamin D if you are taking verapamil.

Diuretics

• Thiazide diuretics

Vitamin D helps the body absorb calcium. Some "Diuretics" increase the amount of calcium in the body. Taking large amounts of vitamin D along with some "Diuretics" might cause too much calcium in the body. This could cause serious side effects, including kidney problems.

Cyclosporine

• Restasis

• Used for: organ transplant, autoimmune conditions

Taking large amounts of vitamin E along with cyclosporine might increase how much cyclosporine the body absorbs. This might increase the effects and side effects of cyclosporine.

Medications changed by the liver

• Atorvastatin

• Simvastatin

• Amlodipine

• Diltiazem

• Cyclosporine

• Tacrolimus

• Midazolam

• Alprazolam

• Rivaroxaban

• Some HIV antiretrovirals

Some medications are changed and broken down by the liver. Vitamin E might change how quickly the liver breaks down these medications. If you are taking medications metabolised by the liver, monitor for any changes in how your medication affects you.

Vitamin E is an antioxidant. There is some concern that antioxidants might decrease the effects of some medications used for cancer. If you are taking medications for cancer, check with your healthcare provider before taking vitamin E.

Vitamin E might slow blood clotting. Taking vitamin E along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

Taking niacin along with the drug simvastatin can increase good cholesterol levels. Taking niacin plus simvastatin along with vitamin E and other antioxidants can decrease the effects of niacin and simvastatin on good cholesterol levels. It is unknown if vitamin E alone decreases the effects of niacin plus simvastatin on good cholesterol levels.

Selumetinib

• Koselugo

Selumetinib, a drug used for cancer, contains vitamin E. Taking selumetinib with vitamin E-containing supplements can result in an unsafe dose of vitamin E. This could increase the risk of bleeding.

Warfarin is used to slow blood clotting. Vitamin E can also slow blood clotting. Taking vitamin E along with warfarin can increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.

Choline Magnesium Trisalicylate

• Trilisate

Rosemary contains chemicals that are similar to choline magnesium trisalicylate. Taking rosemary along with choline magnesium trisalicylate might increase the effects and side effects of choline magnesium trisalicylate.

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

Rosemary might slow blood clotting. Taking rosemary along with medications that also slow blood clotting might increase the risk of bruising and bleeding.

Salsalate

• Disalcid

Salsalate is called a salicylate. Rosemary also contains a salicylate. Taking salsalate with rosemary might increase the risk for side effects from salicylates.

Antibiotics

• Doxycycline

• Ciprofloxacin

• Amoxicillin

• Azithromycin

• Norfloxacin

• Trimethoprim

Zinc might decrease how much antibiotic the body absorbs from the gut. Taking zinc along with quinolone antibiotics might decrease the effects of these antibiotics. To avoid this interaction, take antibiotics at least 2 hours before or 4-6 hours after zinc supplements.

Zinc can decrease the amount of tetracyclines the body absorbs. Taking zinc with tetracyclines might decrease the effects of tetracyclines. To avoid this interaction, take tetracyclines 2 hours before or 4-6 hours after taking zinc supplements.

Bictegravir/emtricitabine/tenofovir alafenamide

• Biktarvy

In theory, zinc might decrease how much bictegravir/emtricitabine/tenofovir alafenamide the body absorbs from the stomach. To avoid this interaction, take bictegravir/emtricitabine/tenofovir alafenamide at least 2 hours before or 6 hours after zinc containing products.

Cephalexin

• Keflex

Zinc can reduce how much cephalexin the body absorbs. This might decrease how well cephalexin works for treating infections. To avoid this interaction, take zinc 3 hours after taking cephalexin.

Cisplatin

• Platinol-AQ

Cisplatin is used to treat cancer. Taking zinc along with cisplatin might inactivate cisplatin therapy. But it's not clear if this is a big concern.

Medications for HIV/AIDS

• Integrase inhibitors

Taking zinc along with integrase inhibitors might decrease blood levels of integrase inhibitors. This might decrease the effects of these medications. Talk to your healthcare provider if you are using integrase inhibitors and want to start taking zinc.

Penicillamine

• Cuprimine, Depen

Zinc might decrease how much penicillamine the body absorbs. Taking zinc with penicillamine might decrease the effects of penicillamine. Take zinc and penicillamine at least 2 hours apart.

Ritonavir

• Norvir

Ritonavir is a drug used for HIV infection. Zinc can reduce how much ritonavir the body absorbs. But it isn't clear if this is a big concern.

Aliskiren

• Tekturna, Rasilez

Aliskiren is moved by pumps in cells in the body. Grapefruit might change how these pumps work, making this medication less effective. Separate taking this medication from consuming grapefruit by at least 4 hours.

Budesonide

• Entocort, UCERIS

Grapefruit might decease how quickly the body gets rid of budesonide. Drinking grapefruit while taking budesonide might increase the side effects of budesonide.

Caffeine

Grapefruit might decease how quickly the body gets rid of caffeine. Drinking grapefruit juice while taking caffeine might increase the side effects of caffeine including jitteriness, headache, and a fast heartbeat.

Grapefruit might decrease how quickly the body gets rid of colchicine. Taking grapefruit juice along with colchicine might increase the effects and side effects of colchicine.

Empagliflozin

Grapefruit might decrease how quickly the body breaks down empagliflozin. Drinking grapefruit juice while taking empagliflozin might increase the effects and side effects of empagliflozin.

Erythromycin

Grapefruit can decrease how quickly the body gets rid of erythromycin. Taking grapefruit juice along with erythromycin might increase the effects and side effects of erythromycin.

Fexofenadine

• Allegra

Grapefruit might decrease how much fexofenadine the body absorbs. Drinking grapefruit juice while taking fexofenadine might decrease the effects of fexofenadine. Separate taking this medication from consuming grapefruit by at least 4 hours.

Fluvoxamine

• Luvox

Grapefruit juice can increase how much fluvoxamine the body absorbs. Drinking grapefruit juice while taking fluvoxamine might increase the effects and side effects of fluvoxamine.

Itraconazole

• Sporanox

Grapefruit juice might change how much itraconazole the body absorbs. But there isn't enough information to know if this interaction is a major concern.

Levothyroxine

• Synthroid, others

Levothyroxine is moved by pumps in cells in the body. Grapefruit might change how these pumps work, making this medication less effective. Separate taking this medication from consuming grapefruit by at least 4 hours.

Losartan

• Cozaar

• Hyzaar

• Used for: high blood pressure, heart failure

The liver activates losartan to make it work. Grapefruit juice might decrease how quickly the body activates losartan. Drinking grapefruit juice while taking losartan might decrease the effects of losartan.

• Caffeine

• Clozapine

• Olanzapine

• Theophylline

• Tizanidine

• Duloxetine

• Ramelteon

Some medications are changed and broken down by the liver. Grapefruit might change how quickly the liver breaks down these medications. If you are taking medications metabolised by the liver, monitor for any changes in how your medication affects you.

• Omeprazole

• Esomeprazole

• Clopidogrel

• Diazepam

• Escitalopram

• Sertraline

• Glipizide

• Phenytoin

• Losartan

Nadolol

• Corgard

Nadolol is moved by pumps in cells in the body. Grapefruit might change how these pumps work. But it's not clear if this is a big concern. Until more is known, follow any instructions on the nadolol label related to intake of grapefruit.

Nilotinib

• Tasigna

Grapefruit juice can increase how much nilotinib the body absorbs. Drinking grapefruit juice while taking nilotinib might increase the effects and side effects of nilotinib.

Grapefruit juice can decrease how quickly the body breaks down oxycodone. Drinking grapefruit juice while taking oxycodone might increase the side effects of oxycodone.

Pitavastatin

Grapefruit juice might decrease how quickly the body breaks down pitavastatin. Drinking grapefruit juice while taking pitavastatin might increase the effects and side effects of pitavastatin.

Prasugrel

Prasugrel needs to be activated by the body to work. Grapefruit appears to decrease how much prasugrel is activated by the body. This might reduce the effects of prasugrel.

Primaquine

Grapefruit juice can increase how much primaquine is available in the body. But it's not clear if this is a big concern or what effects it might have.

Rivaroxaban

Grapefruit juice might decrease how quickly the body breaks down rivaroxaban. Drinking grapefruit juice while taking rivaroxaban might increase the effects and side effects of rivaroxaban.

Saquinavir

• Fortovase, Invirase

Drinking grapefruit juice can increase how much saquinavir the body absorbs. Drinking grapefruit juice while taking saquinavir might increase the effects and side effects of saquinavir.

Sertraline

Grapefruit can decrease how quickly the body breaks down sertraline. Drinking grapefruit juice while taking sertraline can increase the effects and side effects of sertraline.

Sunitinib

• Sutent

Grapefruit might decrease how quickly the body breaks down sunitinib. Drinking grapefruit juice while taking sunitinib might increase the effects and side effects of sunitinib. Until more is known, follow any instructions on the sunitinib label related to intake of grapefruit.

Tadalafil

Grapefruit juice might decrease how quickly the body breaks down tadalafil. Drinking grapefruit juice while taking tadalafil might increase the effects and side effects of tadalafil.

Talinolol

• Cordanum

• Used for: angina, heart conditions

Grapefruit juice can reduce how much talinolol is available in the body. Drinking grapefruit juice with talinolol might reduce the effects of talinolol.

Theophylline

Drinking grapefruit juice might decrease the effects of theophylline. There's not enough information to know if this is a big concern.

Tolvaptan

• Samsca

Grapefruit can decrease how quickly the body breaks down tolvaptan. Drinking grapefruit juice while taking tolvaptan can increase the effects and side effects of tolvaptan.

Warfarin is used to slow blood clotting. Drinking grapefruit juice might increase the effects of warfarin and increase the chances of bruising and bleeding. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.