Low on Vitamin D? Your Medications Could Be to Blame

It’s no secret that vitamin D is very important for healthy bones. But vitamin D is responsible for much more than bones. Recent research shows low vitamin D levels are associated with diseases like rheumatoid arthritis, lupus, multiple sclerosis, and diabetes.

The most well-known causes of vitamin D deficiency are lack of sun exposure, diet, or digestive problems. But medications can also cause low vitamin D — even when someone gets enough from the sun or their diet.  

Why do low vitamin D levels matter?

Vitamin D affects several key body systems. Many people know that vitamin D is essential for strong bones. But muscle function also depends on normal levels of vitamin D because of its balancing effect with the body’s calcium level. It also affects immune function and inflammation in the body.  

Research has linked low vitamin D to everything from diabetes to autoimmune disease and cancer. Even mental health seems to depend on vitamin D: Anxiety and depression are more likely with low vitamin D levels.

Symptoms of low vitamin D

Most of the time, people don’t know they have low vitamin D until they get a blood test. That’s because not everyone feels the effects of low vitamin D. Or if they do, it's easy to assume those symptoms are due to something else. 

Classic symptoms of vitamin D deficiency can include: 

• Bone pain

• Muscle pain

• Weakness

• Trouble walking

 Some people also feel tired or depressed with low vitamin D levels.

Which medications can cause low vitamin D levels?

Most people don’t know it, but certain medications can cause vitamin D deficiency. Medications can do this in two main ways. Some medications speed up the body’s natural process of breaking down vitamin D into its inactive parts. Others reduce the absorption of vitamin D from food and supplements.

The following medications cause the liver to break down vitamin D too quickly:

• Seizure medications: phenobarbital, carbamazepine, oxcarbazepine, phenytoin, primidone, and valproic acid 

• Blood pressure medications: spironolactone and nifedipine

• Steroids: dexamethasone (these medications can significantly affect bone strength because they lower vitamin D levels and reduce calcium absorption)

• Medication for infections: antibiotics (isoniazid and rifampin for tuberculosis), antiretrovirals (ritonavir and saquinavir for HIV), and antifungals (clotrimazole)

• Cancer treatment: taxol and cyclophosphamide

• Estrogen blockers for breast cancer treatment: tamoxifen, anastrozole, and fulvestrant 

• Natural supplements: St. John’s wort and kava kava 

Medications that reduce absorption of vitamin D through the digestive tract are:

• Laxatives 

• Orlistat (used for weight loss)

• Cholestyramine (used for conditions like high cholesterol or chronic diarrhea)

What else can cause vitamin D deficiency?

Besides medications, other common causes of low vitamin D levels are:

• Lack of sun exposure: The skin uses sunlight to make vitamin D. So people can become deficient if they spend most of their time indoors or live in places with little sun. Darker skin, sunscreen, and older age can also reduce sunlight absorption.

• Deficient dietary intake: Foods high in vitamin D include salmon, trout, cod liver oil, and some mushrooms. But many people do not eat these foods frequently. Some foods are fortified with vitamin D, like milk and cereal. And other common foods have smaller amounts of vitamin D, like eggs and cheese.

• Digestive system problems: Even if you get plenty of vitamin D in your diet, your gut still has to be able to absorb it. Celiac disease or gastric bypass surgery can affect vitamin D absorption in the digestive tract.

• Liver or kidney problems: Vitamin D is processed into its active forms through the liver and kidneys. So liver failure (cirrhosis) and kidney failure both cause low vitamin D levels.

Is vitamin D deficiency serious?

Yes. Vitamin D deficiency is serious because it can cause health problems over time if it’s left untreated. It can cause:

• Rickets: When children have vitamin D deficiency, they develop bones that are weak and deformed. That’s because they need vitamin D for their bones to grow normally. 

• Osteomalacia: Vitamin D deficiency can also cause weak and deformed bones later in development — in both teens and adults. 

• Osteoporosis: This is defined by brittle, easily broken bones in older age. Bone density goes down over time from a lack of calcium, vitamin D, or weight-bearing exercise.

Beyond the bones, vitamin D also plays a role in regulating blood pressure and cholesterol, glucose (sugar) levels, brain function, and the immune system. Studies are ongoing to understand all of the effects of low vitamin D in the body. 

Can you get too much vitamin D?

Yes. Since there’s limited vitamin D available in foods, dietary excess is unlikely. Sun exposure does not lead to vitamin D toxicity. But you can get too much vitamin D if you take supplements. High-dose supplements are available over the counter. But, to avoid vitamin D toxicity, you should only take them under medical supervision. 

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Written by:

Shane McCarthy, DO

Shane McCarthy, DO, practices full-spectrum family medicine and is board certified through the American Board of Family Medicine. She has over 20 years of experience.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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