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Vitamin D: The Sunshine Hormone and RA

Today is a glorious, sunny day. Sure, it’s still cold. Brrrrrrrr. But more than one living creature in our household is finding treasured sunny spots in which to lie and soak up the rays.

I was standing in the bathroom, letting the sun warm my back, when my thoughts wandered to summertime, sunshine, and eventually vitamin D.

Vitamin D is fat-soluble vitamin found in a small number of foods. It is also a hormone synthesized in the body when sunlight, specifically ultraviolet B (UV-B) light, reaches exposed skin. Many people do not get enough vitamin D through sun exposure and food alone so they take dietary supplements1.

I am one of those persons.

Being diagnosed with multiple autoimmune diseases, some of which have been associated with vitamin D deficiency, makes getting enough vitamin D important. With rheumatoid arthritis, reduced vitamin D intake has been linked to increased risk of developing the disease, and vitamin D deficiency has been found to be associated with disease activity and musculoskeletal pain in patients with RA2.

Although it was my primary care doctor who first checked my vitamin D levels, it is my rheumatologist and neurologist who monitor my D levels and suggest how much I should take daily.

Since I take methotrexate, a drug which contributes to drug-induced photosensitivity reactions, I need to get my vitamin D in other ways besides the sun. Patients who use methotrexate are instructed to protect their skin from direct sun exposure to avoid phototoxic skin reactions. The SPF protection provided by many sunscreens blocks UV-B light, the type which causes a typical sunburn; but drug-induced photosensitivity reactions are more often caused by UV-A light.

Vitamin D circulates in the body in two forms. The liver converts vitamin D to 25-hydroxyvitamin D3 [25(OH)D3], also known as calcidiol. The kidneys convert calcidiol to activated vitamin D, also known as 1,25-dihydroxyvitamin D [1,25(OH)2D] or calcitriol.

The recommended test that measures vitamin D levels in the blood measures the serum concentration of 25(OH)D3 that is reported as nanomoles per liter (nmol/L) or nanograms per milliter (ng/mL). The following cut-off points are based on a review of data conducted by a committee of the Institute of Medicine (IOM), not by a scientific consensus process1.

  • <30 nmol/L or <12 ng/mL is associated with vitamin D deficiency
  • >50 nmol/L or >20 ng/mL is generally considered adequate for bone and overall health in healthy individualsVitamin D Serum TableVitamin D Serum Table
  • Emerging evidence indicates that >125 nmol/L or >50 ng/mL is associated with potential adverse effects, particularly with levels >150 nmol/L or >60 ng/mL

1 nmol/L equals 0.4 ng/mL.

[Adapted from Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.]

Serum levels greater than 20 ng/mL are considered adequate for about 97.5% of the population, according to the IOM report, and levels greater than 50 ng/mL may cause undesirable adverse effects. However, some rheumatologists (including my own) recommend serum concentrations between 50-80 ng/mL in patients diagnosed with autoimmune disease.

My 25(OH)D3 serum level was 70.3 ng/mL the last time it was tested after years of monitored vitamin D supplementation, whereas it was 7.6 ng/mL at the time I was diagnosed with RA and experiencing a great deal of pain.

I am looking forward to being able to enjoy the sunshine a bit more as the weather warms up. However, I will continue to protect my skin from ultraviolet light and take vitamin D3 supplements each day.

To know how much vitamin D3 you may need to take, please talk to your doctor. It is important to have your blood tested to know where you are starting from before starting on a regimen to increase your levels. For those who are interested, I take a daily supplement of 10,000 IU vitamin D3. My body’s need for vitamin D supplementation is increased by being obese.


This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

  1. Vitamin D - Health Professional Fact Sheet (rev. Nov 14, 2014). National Institutes of Health Office of Dietary Supplements. Accessed Mar 6, 2015 at
  2. Kostoglou-Athanassiou I, Athanassiou P, Lyraki A, Raftakis I, Antoniadis C. Vitamin D and rheumatoid arthritis. Ther Adv Endocrinol Metab. 2012 Dec;3(6):181-187. doi:10.1177/2042018812471070
  3. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010


  • Connie Rifenburg
    4 years ago

    I also take a vitamin D3 supplement daily of 5000 IU after being diagnosed with Vit D deficiency. I was prescribed 50K by my Rheum. Dr. 1 pill once a week for 4 weeks. Then retested. D3 was fine. Then I began taking her first recommendation dose of 400 IU of D3 per day for several months and had another test, it showed that I fell below the normal D3 again.

    At that time, she gave me the 50K again, and when I was done with that, she suggested I try 5000 IU per day and see what happened. I have been on that dose for 6 months and my levels are normal – that is – normal when I take the 5000 IU daily.

    I never looked at the Vit D3 loss as a part of my RA pain, so I’m interested to learn that it helps with pain since I am experiencing a “first” period of months without severe pain. I still take two-15mg oxycodone daily, and 5mg prednisone, but I would say that my pain level is well within limits to do normal daily tasks. I wonder if it is the D3 difference?

    I’m not willing to stop it to find out since the last time I did, it significantly dropped within 2 months. So I’ll accept that whatever the D3 is doing must be helping with the reduction in pain levels in the last 6 months.

    I am very light skinned and have always burned badly during my childhood before SPF was invented. I don’t go out in the sun at all to just sit, and when I am outside, I sit in shade whenever possible or go back inside. I get hives from sunburn..even mild sunburn, so I can’t get D3 that way at all.

    It makes me wonder how many years I had the D3 deficiency before they began testing it. Thanks for the information as to the IOM recommended ratio. I will check my older blood work to see where it was before we began to treat it.


  • Kelly Mack moderator
    4 years ago

    Thanks for this Lisa! I take a monthly supplement for vitamin D under a prescription from my doctor and think it helps support my general health. Really good to know more! Best, Kelly

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