Can Vitamin D Supplements Help Your Psoriatic Arthritis?

Note: The U.S. Food and Drug Administration (FDA) does not approve supplements for safety or effectiveness. Talk to a healthcare professional about whether a supplement is the right fit for your individual health, and about any potential drug interactions or safety concerns.

If you’re living with psoriatic arthritis (PsA), you know it’s more than just joint pain. This chronic disorder causes the immune system to attack healthy cells, triggering joint inflammation, swollen fingers and toes, and itchy, scaly psoriasis skin patches.

“Vitamin D is strongly linked with skin immunity because of its ability to suppress the immune response in skin inflammation, making it a viable treatment for psoriasis,” says Erin Hammett, DO, a rheumatologist at Sansum Clinic in Santa Barbara, California. Simply put, vitamin D may help calm immune system overactivity.

But “modern humans are usually indoors and don’t live with adequate exposure to sunlight,” says Aly Cohen, MD, a Princeton, New Jersey–based rheumatologist and author of the book Detoxify.

• Fatty fish like salmon and mackerel
• Beef liver
• Fortified dairy products
• Egg yolks
• Fish liver oil

“These are good studies that both support the large body of evidence that patients with psoriasis and psoriatic arthritis have lower levels of vitamin D, and that disease activity is higher in patients with low serum levels of vitamin D,” says Dr. Hammett, adding that she sees similar results in her clinical practice.

“Individuals with psoriasis and psoriatic arthritis must have vitamin D levels checked,” Hammett says. “If deficient, they should start supplementation, as it could improve their disease.”

The takeaway? There’s enough evidence to support using vitamin D as a supportive therapy, but not as a standalone treatment for psoriatic arthritis.

“Vitamin D supplements won’t make everything better,” says Dr. Cohen. “But generally, it’s far more appropriate to give patients vitamin D in reasonable amounts than it is not to.”

So, should you consider adding a vitamin D supplement to your psoriatic arthritis treatment regimen?

“Typically, yes,” says Hammett. “Individuals with skin psoriasis tend to have lower vitamin D levels, which can make psoriasis harder to control and flare psoriatic arthritis as well.”

Cohen agrees: “As an immune disease specialist, I tell patients they need to get their vitamin D levels into the high-normal range — that’s when the immune system uses it most effectively and where we see the strongest health outcomes.”

It’s also important to remember that vitamin D supplements are most helpful when used alongside standard medical treatments, not in place of them, she adds.

For people with psoriatic arthritis and healthy individuals alike,15 mcg is often insufficient, says Cohen. There’s no one-size-fits-all vitamin D daily dosage when you have psoriatic arthritis, explains Cohen — it ultimately depends on your baseline vitamin D status and overall health.

Hammett generally recommends daily doses of 2,000 IUs for those with adequate vitamin D levels. Ultimately, though, she says it’s best to start with a simple blood test to check your current vitamin D levels. If your results come back low, your doctor may suggest a different supplement dose to help bring levels up and possibly reduce disease activity.

Here’s Hammett’s general dosing guide for vitamin D3 (the type of vitamin D most often used in supplements) based on blood test results:

• Vitamin D levels of less than 15 nanograms per milliliter (ng/mL): 50,000 IUs per week for six to eight weeks, then 5,000 IUs per day

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• Vitamin D levels of 15 to 20 ng/mL: 5,000 IUs per day

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• Vitamin D levels of 20 to 25 ng/mL: 4,000 IUs per day

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• Vitamin D levels of 25 to 30 ng/mL: 2,000 IUs per day

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Because an excess of vitamin D is risky, regular monitoring is also vital. Cohen recommends getting a follow-up blood test three to four months after starting supplementation to check your vitamin D levels and adjusting your supplement dose if necessary.

• Vitamin D plays a meaningful role in immune regulation and inflammation, making it a promising supportive therapy for people with psoriatic arthritis (especially those who are deficient).
• Research shows a strong link between low vitamin D levels and more severe psoriasis and psoriatic arthritis, though more high-quality studies are needed to confirm how much supplementation can reduce symptoms.
• Before starting supplements, talk to your doctor about getting your vitamin D levels tested, since the right dose depends on your current levels. Supplementing without knowing your levels may lead to ineffective dosing or potential toxicity.
• Vitamin D should be used as a complement to — not a replacement for — standard psoriatic arthritis treatments. If you’re deficient, correcting that can be a step toward more effective psoriatic arthritis management.