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Vitamin D Supplement Improves Blood Sugar After Surgery in Elderly

Sep 25, 2021
Editor: Steve Freed, R.PH., CDE

Author: Eric Cheung, PharmD Candidate, USF Taneja College of Pharmacy

Knee surgery patients who are at increased risk for high blood sugar due to age and limited mobility post-surgery may benefit from vitamin D. 

Vitamin D has been known to help with bone growth and protection because it helps in bone mineralization. It is an essential vitamin that many providers have found to be low in their patients; thus, they will recommend daily or weekly supplements. Regarding diabetes treatment, vitamin D is thought to aid the pancreas’ beta cells and ultimately improve insulin secretion. Previous studies have shown the benefits of regularly taking vitamin D to support type 1 and type 2 diabetes patients. Those benefits seen were the improvement of A1c, fasting blood glucose, and even insulin sensitivity. This study wanted to observe those effects on elderly type 2 diabetes patients who have received knee surgery, to further understand vitamin D’s impact.


The purpose of this study is to investigate the doses of 800 IU and 2000 IU of vitamin D for 24 months in elderly adults after knee surgery. This specific population is chosen because of several factors that may increase their blood sugars after their surgery: the age, limited mobility post-surgery, and the surgery itself are factors that would risk increasing blood sugar. The study is a randomized, double‐blind trial conducted from 2008 to 2014 in Zurich, Switzerland, to measure the two different doses of vitamin D and fasting blood glucose and insulin resistance. The data were analyzed using linear mixed models adjusted for age, sex, baseline vitamin D deficiency, and body mass index.

Two hundred fifty-one participants were enrolled in this study with varying ages, gender, glucose intolerance, fasting blood glucose, and vitamin D level at baseline. The primary outcome results, comparing a difference between 800 IU and 2000 IU, have been statistically insignificant.  FBG between the group receiving 800 IU after two years was 5.32 (95% CI: [5.19 to 5.44]) and 2000 IU after two years was 5.39 (95% CI: [5.27 to 5.51]) mmol/L (P = .130). In addition, there was no difference in insulin resistance seen between the 800 IU having the result of 0.44 (95% CI: [0.37 to 0.52] vs. the 2000 IU with the outcome of 0.49 (95% CI: [0.41; 0.58]), P = 0.162.

The study showed the statistical significance of lowering fasting blood glucose in the 800 IU and 2000 IU. Groups. The results in the 800 IU group are from 5.54 (95% CI: [5.42 to 5.66]) to 5.32 (95% CI: [5.19 to 5.44]), P < .001. The results in the 2000 IU group are from 5.5 (95% CI: [5.38 to 5.62]) to 5.39 (95% CI: [5.27 to 5.51]), P = 0.019. The results have shown that there are no statistical differences and no clinical differences between the two doses. The results have established an excellent discovery for this specific patient population since they have factors that will increase their blood sugar.

In conclusion, there are no statistical nor clinical differences between the 800 IU and 2000 IU. Vitamin D doses in elderly patients who had knee surgery. The results indicated that the significant benefit of taking vitamin D was the decrease in fasting blood glucose. Interestingly, the more potent dose of vitamin D did not provide a more desirable outcome. The similar effects between the two strengths could be due to age and the body’s ability to absorb the vitamin D to be utilized. Vitamin D’s role in helping lower fasting blood glucose is promising since this patient group has a higher risk of increasing their blood sugar levels due to physical activity limitations. This study’s weaknesses are that it lacks a placebo group, and there was no distinction of sun exposure, which could contribute to those taking the lower dose of 800 IU having high vitamin D levels.

Practice Pearls:

  • Vitamin D 800 IU and 2000 IU have no statistical nor clinical differences when measuring fasting blood glucose and insulin resistance.
  • After knee surgery, taking vitamin D results in lower fasting blood glucose levels, with similar results between 800 IU and 2000 IU.
  • Adding vitamin D supplementation for type 2 diabetes patients with limited mobility due to knee surgery improves fasting blood glucose, insulin concentration, insulin resistance, and insulin sensitivity.


Baranwal M. Vitamin D Supplement Improves Blood Sugar After Knee Surgery In Elderly. Published: Med Dialogues 2021 Jan20.

Grubler MR, Gangler S. Effects of vitamin D3 on glucose metabolism in patients with severe osteoarthritis: A randomized, doubleblind trial comparing daily 2000 with 800 IU vitamin D3. Diabetes Obesity and Metabolism 2020 December 28.


Eric Cheung, PharmD Candidate, University of South Florida Taneja College of Pharmacy