New prescription? Here is what you need to know about interactions and depletions.

April 2021

If you are taking any prescription medications, you may wonder if it is safe to also take over-the-counter supplements: that is a reasonable concern. Many common supplements are known to interact with prescription drugs. But that does not necessarily mean you should not take any supplements. Depending on what supplements — and drugs — you take, there may be no problem at all. In fact, some medications can cause deficiencies or side effects that may be minimized by adding a supplement to your daily routine.

Here are some common examples of supplements you may need to avoid if you are taking certain prescription medications — and of other supplements you will want to take.

Supplements that interact with medications

Supplements can interfere with how your body processes prescription drugs. Supplements can cause the level of medication in your body to increase or decrease and can cause other unintended consequences. These consequences can have a negative impact on your health and on the disease the medication was prescribed to treat.

If you are taking any supplements, be sure to talk to your pharmacist about whether they may interact with any drugs your doctor prescribes. Below are just a few of the many common supplements known to interact with prescriptions medications.

Vitamin K
Vitamin K is an essential vitamin that is important for helping the blood to clot and therefore for preventing excessive bruising and bleeding.

Vitamin K is naturally occurring in many foods and is included in most multivitamins. Problematic drug interactions can occur between vitamin K and several drugs, most notably these two medications that directly impact the blood:

  • Warfarin (brand name: Coumadin), a blood thinner used to prevent blood clots.
  • Anisindione (brand name: Miradon), an anticoagulant.

If you are taking either of these medications, you should avoid taking vitamin K as a separate supplement, as these typically contain large doses of vitamin K. If you wish to take a multivitamin that contains vitamin K, be sure to talk to your doctor first.

Milk thistle
Milk thistle is a supplement that some people take for liver disorders. Common possible drug interactions include the following:

  • Deferiprone — a medication that treats iron overload.
  • Raloxifene — a medication that treats osteoporosis in women.
  • Simeprevir — a medication used to treat hepatitis C.

Licorice root
Licorice root is a supplement that some people take for digestive disorders.

There are 138 moderate and 4 minor interactions known to occur between licorice root and various medications. The most commonly checked of the moderate interactions is that with digoxin, a medication used to treat heart failure.

Medications that deplete certain vitamins

Whereas it is important to take all medications as prescribed, it is also important to note that some medications taken over the long term can deplete certain vitamins. Here are some common medications that can potentially cause certain depletions.

Metformin (used for diabetes and prediabetes)
Metformin is a common medication prescribed to treat diabetes and prediabetes. Long-term use of metformin may lead to B-12 deficiency, which in turn can lead to anemia and other symptoms, such as depression, confusion and dementia. The recommended daily dose of B-12 is 2.4 mcg, although you should ask your doctor if you need a stronger dose if you have B-12 deficiency.

Methotrexate (uses include psoriasis, rheumatoid arthritis and leukemia)
Methotrexate is a medication used to treat severe psoriasis and rheumatoid arthritis. It is also used to treat leukemia and certain kinds of cancer. Methotrexate reduces the amount of folic acid in the body, which can lead to folic acid deficiency. This can lead to anemia and birth defects. If you are taking methotrexate, talk to your doctor about whether folic acid supplements are right for you — and what dose you should be taking.

Corticosteroids (uses include COPD, arthritis and transplanted organs)
Some people may take anti-inflammatory corticosteroids (such as prednisone) for a couple of weeks. However, other people — such as those with COPD (Chronic obstructive pulmonary disease), bad arthritis or transplanted organs — may be on them for the long term. When used for more than a short duration, corticosteroids can lead to osteoporosis. Although these drugs do not directly decrease calcium and vitamin D (two key components of building and maintaining strong bones), making sure you have a sufficient daily intake of calcium and vitamin D is important.

Experts recommend 1000 mg/day of calcium and 400–800 IUs (10 –20 mcg) per day of vitamin D.

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