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The short answer

Some common, long-term medications quietly lower a vitamin or mineral, by reducing absorption, increasing urinary loss, or blocking the pathway your body uses to make or use the nutrient. The best-documented examples are metformin and vitamin B12, long-term proton pump inhibitors and magnesium, diuretics and potassium or magnesium, and methotrexate and folate. Most depletions build slowly over months to years, are easy to monitor with a blood test, and are managed by your prescriber rather than by stopping the drug. This page lists the well-established ones with the mechanism, what to watch for, and the source, so you can have a more informed conversation with your pharmacist.

The most common drug-nutrient depletions

The table below covers depletions that are well documented in drug labeling and clinical guidelines. It is a reference for discussion with your clinician, not a prompt to self-treat. The right response to most of these is a blood test and a conversation, not an automatic supplement.

Medication (class / example) Nutrient affected What happens What to watch for / do Source
Metformin (biguanide) Vitamin B12 Reduces B12 absorption in the lower small intestine; risk rises with higher dose and more years of use. Periodic B12 testing for long-term users; report numbness, tingling, or fatigue. Do not stop metformin on your own. ADA Standards of Care in Diabetes 2026; metformin label
Proton pump inhibitors (omeprazole, esomeprazole, pantoprazole) Magnesium; vitamin B12 Long-term acid suppression can lower magnesium and, over years, reduce B12 absorption. FDA advises baseline and periodic magnesium for long-term users, especially with diuretics; watch for muscle cramps or palpitations. FDA Drug Safety Communication, March 2011
Loop diuretics (furosemide, bumetanide) Potassium, magnesium, thiamine Increase urinary loss of potassium, magnesium, and thiamine (vitamin B1). Electrolytes are commonly monitored; report weakness, cramps, or palpitations. NIH ODS fact sheets; FDA labeling
Thiazide diuretics (hydrochlorothiazide) Potassium, magnesium Increase urinary potassium and magnesium loss. Note: thiazides tend to retain calcium rather than deplete it. Electrolyte monitoring; potassium intake adjusted by your clinician. NIH ODS; FDA labeling
Methotrexate (low-dose, for RA or psoriasis) Folate Acts as a folate antagonist, which is the basis for routine folic acid co-prescription. Folic acid is standard alongside low-dose methotrexate to reduce side effects; follow your rheumatologist's plan. American College of Rheumatology guidance; methotrexate label
Isoniazid; hydralazine Vitamin B6 (pyridoxine) Interfere with vitamin B6 metabolism, which can contribute to peripheral neuropathy. Vitamin B6 is commonly co-prescribed with isoniazid to prevent neuropathy. CDC and ATS tuberculosis guidance; isoniazid label
Long-term corticosteroids (prednisone) Calcium, vitamin D Reduce calcium absorption and bone density with prolonged use. Calcium plus vitamin D and bone-density monitoring are standard for long-term steroid use. ACR glucocorticoid-induced osteoporosis guidance
Statins (atorvastatin, simvastatin) Coenzyme Q10 (CoQ10) Block the same pathway the body uses to make CoQ10, which lowers blood CoQ10 levels. Honest note: lower CoQ10 levels are real, but clinical trials have not shown that CoQ10 supplements reliably relieve statin muscle symptoms. Discuss before supplementing. NIH ODS; randomized trials (mixed results)
Levothyroxine (absorption, not depletion) Calcium, iron (timing) Calcium or iron taken at the same time reduces levothyroxine absorption. Separate levothyroxine from calcium or iron supplements by about 4 hours. FDA levothyroxine prescribing information

Sources: FDA drug labeling and the March 2011 Drug Safety Communication on PPIs and magnesium; American Diabetes Association Standards of Care in Diabetes 2026; American College of Rheumatology guidance; NIH Office of Dietary Supplements fact sheets.

How a medication can lower a nutrient (the three mechanisms)

1. Reduced absorption. The drug changes the gut environment so less nutrient is taken in. Metformin reduces B12 uptake in the ileum, and long-term acid suppression from proton pump inhibitors reduces the stomach acid needed to release B12 and absorb some minerals.

2. Increased loss. The drug increases how much nutrient leaves the body in urine. Loop and thiazide diuretics increase urinary potassium and magnesium loss, which is why electrolytes are often checked on these medicines.

3. Blocked production or use. The drug interferes with a pathway that makes or activates the nutrient. Statins lower the body's own production of CoQ10, and methotrexate antagonizes folate, which is why folic acid is co-prescribed.

The honest part: not every depletion needs a supplement

A lower blood level of a nutrient is not the same as a deficiency that causes harm, and replacing it is not always proven to help. The clearest example is CoQ10 and statins. Statins genuinely lower CoQ10 levels, and CoQ10 supplements are heavily marketed for statin-related muscle aches, but randomized trials have not shown a reliable benefit. We say that plainly because the goal here is an accurate picture, not selling a supplement. Some depletions are routinely supplemented under medical guidance (folic acid with methotrexate, vitamin B6 with isoniazid); others are best handled by testing the blood level and supplementing only if it is actually low. Your pharmacist can tell you which bucket yours is in.

What to do with this information

Bring your full list of prescriptions and supplements to your next pharmacy or doctor visit and ask two questions: "Does anything I take regularly lower a vitamin or mineral?" and "Should I have a blood level checked?" If you take metformin, ask about vitamin B12. If you take a proton pump inhibitor long term, ask about magnesium, especially if you are also on a diuretic. Do not stop a prescribed medication to avoid a depletion; the condition the drug treats is almost always the bigger risk, and depletions are manageable with monitoring. Also remember that some supplements interact with medications on their own, so confirm any new supplement before you start it.

Check a Drug and Supplement Combination

Use our free interaction checker to search drug, supplement, and food combinations, including nutrient interactions.

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Frequently Asked Questions

What is drug-induced nutrient depletion?

It is when a medication lowers the body's level of a vitamin or mineral, by reducing how much is absorbed, increasing how much is lost in urine, or blocking the pathway the body uses to make or use the nutrient. Well-documented examples include metformin lowering vitamin B12, long-term proton pump inhibitors lowering magnesium, and loop diuretics increasing loss of potassium and magnesium. Depletion usually develops slowly over months to years of regular use.

Does metformin deplete vitamin B12?

Yes. Long-term metformin use can reduce vitamin B12 absorption, and the risk increases with higher doses and more years of use. The American Diabetes Association suggests periodic vitamin B12 testing for people on chronic metformin, especially at doses of 1,500 mg per day or more, after about 4 to 5 years, or if symptoms like numbness, tingling, or anemia appear. Talk to your prescriber about testing and, if needed, B12 supplementation. Do not stop metformin on your own.

Should I take a supplement to replace what my medication depletes?

Not automatically. Some depletions are routinely managed with supplements under medical guidance (folic acid with low-dose methotrexate, vitamin B6 with isoniazid), while others are managed by monitoring blood levels and supplementing only if they fall low. A few popular pairings, such as CoQ10 for statin muscle symptoms, are mechanistically plausible but not proven to help in clinical trials. Because some supplements can themselves interact with your medication, confirm any supplement with your pharmacist or doctor first.

How do I check whether my medication interacts with a supplement?

Use a drug interaction checker that includes supplements, and bring your full medication and supplement list to your pharmacist. Timing also matters: some supplements, such as calcium and iron, reduce absorption of medications like levothyroxine when taken at the same time, so they are separated by several hours rather than avoided entirely.

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