Quick answer

Ask your pharmacist or doctor before combining. NIH says corticosteroids such as prednisone can reduce calcium absorption and impair vitamin D metabolism. In a US survey, very low vitamin D levels were more than twice as common among oral steroid users (11%) as among nonusers (5%).^1,2

Key facts

NIH's consumer sheet says steroids such as prednisone can lower your blood levels of vitamin D.²
The prednisone label says corticosteroids decrease bone formation and increase bone resorption through their effect on calcium regulation, meaning less absorption and more excretion.³
The same label lists calcium and vitamin D supplementation among the first-line measures to consider when long steroid treatment is expected, alongside exercise and bone medicines.³
MedlinePlus says your doctor may prescribe or recommend a calcium or potassium supplement with prednisone and tells people to follow those directions carefully.⁴

Your doctor may want to check on you

Corticosteroid tablets such as prednisone can reduce calcium absorption and interfere with how the body uses vitamin D. In a US survey, very low vitamin D levels were twice as common among people taking oral steroids (11%) as among those who were not (5%).^1,2

Reported in studies

Do corticosteroids lower vitamin D?

NIH says they can. Its health professional sheet says corticosteroid medications such as prednisone can reduce calcium absorption and impair vitamin D metabolism, and its consumer sheet puts it plainly: steroids can lower your blood levels of vitamin D.^1,2

The numbers come from a US survey covering 2001 to 2006. A blood level below 10 ng/mL (25 nmol/L) was more than twice as common among children and adults who reported oral steroid use (11%) as among nonusers (5%). A survey comparison shows how common low levels were in each group. It does not prove the medicine caused them, and it does not say how long anyone took the steroid.¹

What do the prednisone label and MedlinePlus say about calcium and vitamin D?

The prednisone label spends more time on bone than on vitamin D. It says corticosteroids decrease bone formation and increase bone resorption through their effect on calcium regulation, meaning less absorption and more excretion, and that osteoporosis can develop at any age. It then lists calcium and vitamin D supplementation, a class of bone medicines called bisphosphonates and weight-bearing exercise among the first-line measures to consider when long treatment is expected.³

MedlinePlus says that, with prednisone, your doctor may instruct a low-salt, high-potassium or high-calcium diet and may prescribe or recommend a calcium or potassium supplement. It tells people to follow those directions carefully. It does not name vitamin D.⁴

That is why this page asks who decides, not whether to avoid the combination. Your prescriber weighs how long you will take the steroid, your bone health and your blood tests, and this page gives no amount.

Does this cover steroid creams, inhalers and injections?

NIH's example is prednisone, and its survey counted people who reported oral steroid use. The sources checked do not address steroid creams, inhalers or injections for vitamin D. That gap is not a finding either way, and your pharmacist can advise on the form you use.¹

Where else does vitamin D turn up?

NIH says vitamin D is found in multivitamin and mineral supplements and in products that combine it with a few other nutrients, and that its upper limit for adults is 100 mcg (4,000 IU) a day from all sources. NIH adds that a provider might recommend more than the upper limit for a period of time to treat a deficiency. That is a clinical decision made with blood results, not something to start alone.²

Questions to put to your prescriber

How long will I take the steroid, and does that change whether I need vitamin D or calcium?
Has my vitamin D level been measured, and should it be checked again?
Do my multivitamin or calcium product already contain vitamin D?
Should I ask about the other measures the label lists, such as exercise and bone medicines?

Questions people ask

Do steroids lower vitamin D?

NIH says corticosteroids such as prednisone can reduce calcium absorption and impair vitamin D metabolism, and its consumer sheet says they can lower blood levels of vitamin D.^1,2

Can you take vitamin D with prednisone?

Ask your prescriber. NIH says prednisone can lower vitamin D levels, and the prednisone label lists calcium and vitamin D supplementation among measures to consider for long treatment, as a decision for the prescriber.^2,3

Which steroids does this cover?

NIH's example is prednisone, and its survey counted oral steroid use. The sources checked do not address creams, inhalers or injections, so ask your pharmacist.¹

Who decides whether to add vitamin D during steroid treatment?

Your prescriber, who knows how long you will take the steroid and what your blood tests show. NIH and the label describe the concern but give no advice for an individual.^1,3

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.