Vitamin D for Diabetes?

Vitamin D — often called the “sunshine vitamin” because it develops from the skin’s exposure to sunlight — has long been recognized as crucial to bone health; it helps the body absorb calcium and thus maintain a healthy bone mineral density. Many of its other roles in the body, however, are not as well understood. Some evidence, though, points to a role in aiding insulin secretion in the pancreas — which means that it could potentially be important for people with Type 2 diabetes.


Many studies of vitamin D have been observational, meaning that researchers simply recorded data without measuring the effects of an intervention. This usually entails measuring the blood level of vitamin D in participants (or, in the case of supplements, recording who already takes them) and then seeing if this level corresponds to certain outcomes. For studies related to diabetes, this often means seeing who develops diabetes or, if the study involves people with diabetes, who has a higher or lower HbA1c level after a period of time. With all observational studies, however, it is possible that factors other than the one being tested — in this case, vitamin D blood level (or intake) — are responsible for the outcome being measured. For example, getting more exercise could result in being outdoors more often and thereby getting more sunlight and vitamin D — and if someone has a lower diabetes risk as a result, it could be because of the exercise and not the vitamin D.

Two recent studies attempted to get around this problem, but in different ways and measuring different outcomes. One study, published in the March issue of the journal Diabetes Care, explored the connection between blood levels of vitamin D and the incidence of Type 2 diabetes in older women. This was an observational study, following 5,140 women with an average age of 66 — who started out without diabetes — for an average of 7.3 years, after measuring their vitamin D level. According to a Reuters article on the study, it initially appeared that vitamin D had some preventive effect against developing diabetes; however, when the researchers adjusted for differences among the participants in body weight, exercise level, and dietary habits, vitamin D was no longer found to make a difference.

The other study was a randomized clinical trial, thus eliminating the uncertainty about causation inherent in observational studies. Published in the February issue of the American Journal of Clinical Nutrition, this study explored the effect of a vitamin-D-fortified yogurt drink on 90 people with Type 2 diabetes. Participants were assigned to drink either plain yogurt, yogurt with added vitamin D, or yogurt with added vitamin D plus calcium, twice a day for 12 weeks. Both of the groups that received vitamin D had a lower HbA1c level (0.4% lower), a smaller waist circumference (3.6 cm less for vitamin D; 2.9 cm less for vitamin D plus calcium), and a lower body-mass index than the group that received the plain yogurt drink. As a different Reuters article on this study notes, however, the results are complicated by the fact that HbA1c in the plain-yogurt group actually rose unexpectedly, as well as by the small size of the study.

Do you take a vitamin D supplement — or do you make an effort to get enough vitamin D from the sun, or from your diet? Do you believe vitamin D has an effect on your diabetes control? Given the conflicting evidence on optimal vitamin D levels — both in the blood, and how much to consume — whom do you trust for guidance concerning how much vitamin D to get? Leave a comment below!

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  • Cathy

    I was advised by my gynecologist at my last visit to incorporate 1200 units of calcium and 1000 of vitamin d into my regimen. So I did. Thankfully they make one pill with both those amounts so it is not so cumbersome. She wanted me to do it for the benefit to my bones. I live in Georgia so I get a LOT of sun but she still wanted me to do the vitamins too as a precaution. I have been taking them since August 2010 – haven’t seen that much change in my diabetes, though.

  • Tom

    I was advised by my cardiologist to take high dose of vitaminD as my level was way low and I was complaining of achy muscles and constant soreness. After the initial dosage It was reduced to 1000 mg two times daily. No significant changes in glucose readings. It has now been 18 months and was normal all this time. Also still feeling achy and sore most of the time especially in damp rainy weather.

  • Jane

    Recently I had a bone density test which showed my bones as strong as a 20-year-old per my MD and I am 76! Years ago I was diagnosed with osteopenia and began taking supplemental calcium and Vit. D and have never stopped. Recently I researched whether one can have too much calcium and found there is no top limit.
    I get about 2000 units a day of calcium + above the minimum required levels of D. In spite of chronic conditions like diabetes and hypertension, I feel very healthy.

  • Lydia

    I am one of nine children. My Mother and her Mother both had diabetes. Out of my siblings; a younger brother and myself are the only ones who have not been diagnosed as being Diabetic.
    I am 63 and have been very religiosly taken vitamins since age 30. I take at least 1500mg of Calcium daily and about 1 year ago started taking 2000mg a day of Vitamin D. Talking with my siblings; only one other has been on a vitamin regiment. I firmly believe Calcium and Vitamin D play an important role in Diabetic prevention.

  • Sandy

    When I was diagnosed with type II, the endocrinologist also noted that my D level was very low and recommended 2,000 per day. It may have been a contributing factor in the rapid decrease of my blood glucose level. I read an article from the Life Extension Foundation which states that the old maximum of 2,000 mg daily was too low, according to their lab results and recommended up to 5,000mg per day. I increased my intake to 4,000 mg per day and saw my glucose level drop by 40. I also take 500 mg of calcium daily.

  • Henry Lahore

    Overview of Diabetes and Vitamin D
    In a nutshell:
    * Appears that >2,000 IU will PREVENT
    * Appears that >4,000 IU will TREAT, but not cure
    * Appears that Calcium and Magnesium are needed for both PREVENTION and TREATMENT
    o which are just some of the vitamin D co-factors

    Includes scores of hyperlinks and many graphs.

  • Mike

    I have type 2 Diabetes and have had it for about 10 years now, just recently told to take 1,000 IU per day as my “D” level was slightly low after the 3rd day found my sugar levels were lower and per my meter the 30 day average was about 20 points lower than before. “I am sold” now don’t get me wrong I do get some higher numbers but that’s from eating too much of what I should not have, all in all I’m happy

  • Shane

    Hey all
    I have had uncontrolled diabetes since 2008. Blood sugar levels ranged from 240 to 400 with insulin and meds. Feb 2010 had a visit to docs office , blood test revealed very low vitamin D.
    Doctor started me in D2 50,000 units twice a week (50,000 is correct). Took about a week to see any results but the results were huge. Started to have blood sugar levels crash down to 40 & 50 range – never had that to happen before (scary) . Cut my insulin injections down to 10 units twice a day , before D2, I was injecting 60 units twice a day and also 15 units of fast acting insulin after meals. Cut the fast acting insulin out altogether.
    I know everyone’s body chemistry is different, but for me D2 was heaven sent. Kind of has me wondering why the doctors hasn’t test my D levels in the past 2 years . I myself would have never thought I was vitamin D deficient as I spend a lot of time outside and in the sun.
    I hope this info serves to help others.
    My blood sugar levels have remained constant 70 to 90 after reducing my insulin inject and remaining on D2.

    PS – Prescription reads = VIT D2 1.25mg (50,000 unit) .

  • Debbie

    My mom, 73, has battled diabetes for many years and within the last couple added medication to help. When the levels were still running higher than desired, her doctor prescribed 50,000 IU of Vitamin D once a week. Her blood sugar levels have dramatically improved! She is now being reduced on the Vitamin D intake to twice a month, but both the Vitamin D & blood sugar levels will be monitored.