Do Vitamins Interfere With Your Medication? It’s Time to Find Out!

Did you know that more than ONE-THIRD of all Americans take some kind of dietary supplement, including a large majority that uses recreational or medicinal after getting a marijuana card? In addition to marijuana prescriptions, medicines such as supplements for bone health and osteoarthritis are also common reasons for taking supplements.

Taking OTC Medication and Supplements

When you take prescription or over-the-counter (OTC) medications, have you considered whether you also take a vitamin, mineral, or other dietary supplements?

Have you considered the possibility of any danger in combining medications and vitamins?  Perhaps this is something you can bring up with your medical marijuana dispensaries, however, the fact is that certain dietary supplements can change absorption, metabolism, or excretion of a medication and thus affect its action in the body. When this happens, you may be getting either too much or too little of the medication you need. This means that they can weaken your medications and make them less effective, or they might make your prescriptions more powerful.

Vitamins and minerals aren’t the bad guys here – they serve crucial functions in almost all of your body’s processes. They must be obtained from foods or supplements, as our bodies are unable to make them. The results of the National Health and Nutrition Examination Survey show that in America, nearly 52% of adults take dietary supplements.

Common Vitamins and Potential Drug Interactions

Vitamin A

This is a fat-soluble vitamin found in certain foods, like red meat, liver, yellow-orange fruits, and vegetables such as carrots. It’s also found in milk, and dark green, leafy vegetables. Vitamin A is not usually available as a supplement on its own. Instead, it can be found as a component of multivitamins and combination supplements targeted towards improving skin, hair, and nails. This can only become a cause for concern when Vitamin A is combined with the use of products that are considered ‘retinoids’. These are compounds that are chemically similar to vitamin A.

Certain kinds of acne and psoriasis medication contain retinoids like isotretinoin and acitretin. Those taking these medications may accidentally experience a Vitamin A overdose, which is why it’s important to be aware of Vitamin A overdose symptoms. These are: nausea, vomiting, feeling dizzy, blurry vision, and a lack of muscle coordination.

Vitamin B6

Vitamin B6 is a water-soluble vitamin that may be used to treat some types of anemia. Foods such as meats, whole grains, and some fruits and vegetables contain high levels of Vitamin B6. However, this vitamin has been shown to reduce the efficacy of drugs such as phenytoin and levodopa.

It is important to note that this effect is not seen when levodopa is prescribed in combination with carbidopa, which is usually the case. This is why healthcare professionals should advise their patients to avoid any food containing Vitamin B6, because even small doses may be enough to inhibit levodopa.

Vitamin E

Vitamin E is a fat-soluble vitamin that is used to assist in the treatment of many conditions, including atherosclerosis, Alzheimer’s, and various cancers. It is also a standard supplement taken by patients with heart disease. However, there have been reports of a higher risk of bleeding in patients that take Vitamin along with the anticoagulant warfarin. This effect occurs in patients taking larger doses of vitamin E (>800 IU), and not the smaller doses found in multivitamins.

Vitamin K

Vitamin K is usually prescribed to mitigate the supratherapeutic international normalized ratio (INR) that is caused by warfarin. When warfarin and vitamin K–containing products are taken concomitantly, the effect of warfarin is reduced. This leads to a decreased prothrombin time and INR, and can be dangerous as it puts the patient at risk for anticoagulation effects that are insufficient, which can lead to conditions such as deep venous thrombosis, pulmonary embolism, myocardial infarction, or worse, a stroke. Some food sources of Vitamin K are green, leafy vegetables like spinach and broccoli.


Niacin is a B-complex vitamin that treats hyperlipidemia and a disorder known as pellagra. Patients may try to treat high cholesterol with a niacin supplement, however, we have found that the combination of niacin and HMG-CoA reductase inhibitors (statins) has been shown to increase the risk of myopathy or rhabdomyolysis. The use of niacin with statins should be suggested only if the benefits of lipid-lowering are greater than the risks of myopathies and rhabdomyolysis.

Folic Acid

Folic acid is a B-complex vitamin. It is used to treat and prevent folic acid deficiency. Folic acid supplementation is usually prescribed during pharmacological therapy with methotrexate as prophylaxis against drug toxicity in patients with rheumatoid arthritis and psoriasis. It is recommended that folic acid supplementation in patients taking methotrexate for rheumatoid arthritis or psoriasis, particularly if the toxicity such as blood cell counts, mucositis, and diarrhea, are present.

You Can Prevent Adverse Drug Reactions to Vitamins By Following These Steps

  1. Tell your doctor about the medicines and supplements you are taking, bring a list if you have to.
  2. Tell your doctor about any changes in your health, recent illness, pregnancy, or surgery history.
  3. If you are prescribed a new medicine, ask your doctor about the following:
    • Can I take this with the other medicines I am using?
    • Should I avoid certain foods, beverages, or other products?
    • What are possible drug interaction signs I should know about?
  4. Read all labels on any over-the-counter and prescription medicines you take

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