Effect of vitamin D supplementation on HbA1c level in a cohort of type 1 diabetic patients

  • Mohammed Yaseen Ahmed Rapareen Pediatric Hospital, Erbil, Iraq.
  • Dlair A.K. Chalabi Department of Pediatrics, College of Medicine, Hawler Medical University, Erbil, Iraq.
Keywords: Diabetes, Deficiency, Vitamin D


Background and objective: Glycemic control is essential to halt the progression of diabetic complications. Some studies previously showed the effect of vitamin D on pancreatic β-cell function and insulin secretion. This study aimed to assess the effect of vitamin D supplementation on HbA1c in patients with type 1 diabetes and vitamin D deficiency.

Methods: This prospective quasi-experimental study was conducted in Erbil city from 1st September to 1st December 2019. In this study, 76 patients attending Layla Qasim diabetic center were tested. Only 50 patients were recruited that had vitamin D deficiency (25OHD: <20) and were aged less than 18 years. They received vitamin D supplementation for 12 weeks. HbA1c and vitamin D level was measured before and after supplementation.

Results: Before vitamin D supplementation, the mean level of serum 25(OH)D among females (8.67 ± 2.56) was lower than males (14.31 ± 3.19). However, no association was found between the initial HbA1c level and gender. HbA1c level (mean = 8.24 ± 0.49) improved significantly after vitamin D supplementation to the level of 7.93 ± 0.67 (P = 0.032). There was a significant difference between groups of glycosylated hemoglobin levels of (first tertile<7.5%, second tertile 7.6%-9.9%, third tertile ≥10%) after 12 weeks of supplementation with vitamin D (P <0.001).

Conclusion: Vitamin D supplementation in type 1 diabetic patients with vitamin D deficiency lead to significant improvement in HbA1c level.


Kahanovitz L, Sluss PM, Russell SJ. Type 1 Diabetes - A Clinical Perspective. Point Care. 2017; 16(1):37–40. https://doi.org/10.1097/POC.0000000000000125.

Katsarou A, Gudbjörnsdottir S, Rawshani A, Dabelea D, Bonifacio E, Anderson BJ, et al. Type 1 diabetes mellitus. Nat Rev Dis Primers. 2017; 3(1):1–7. https://doi.org/10.1038/nrdp.2017.16.

Rewers M, Ludvigsson J. Environmental risk factors for type 1 diabetes. Lancet. 2016; 387(10035):2340–8. https://doi.org/10.1016/S0140-6736(16)30507-4.

Patterson CC, Gyürüs E, Rosenbauer J, Cinek O, Neu A, Schober E, et al. Trends in childhood type 1 diabetes incidence in Europe during 1989-2008: evidence of non-uniformity over time in rates of increase. Diabetologia. 2012; 55(8):2142–7. https://doi.org/10.1007/s00125-012-2571-8.

Harvard Medical School. Type 1 Diabetes Mellitus: What is it, Boston, USA: Harvard Medical School; 2018. https://www.health.harvard.edu/a_to_z/type-1-diabetes-mellitus-a-to-z. Accessed 2 Apr 2020.

Florkowski C. HbA1c as a Diagnostic Test for Diabetes Mellitus - Reviewing the Evidence. Clin Biochem Rev. 2013; 34(2):75–83.

National Institutes of Health. Vitamin D: Fact Sheet for Health Professionals USA: NIH. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional. Accessed 8 Apr 2020.

Christakos S, Hewison M, Gardner DG, Wagner CL, Sergeev IN, Rutten E, et al. Vitamin D: beyond bone. Ann N Y Acad Sci. 2013; 1287(1):45–58. https://doi.org/10.1111/nyas.12129.

Hummel D, Aggarwal A, Borka K, Bajna E, Kállay E, Horváth HC. The vitamin D system is deregulated in pancreatic diseases. J Steroid Biochem Mol Biol. 2014; 144(Pt B):402–9. https://doi.org/10.1016/j.jsbmb.2014.07.011.

Sung CC, Liao MT, Lu KC, Wu CC. Role of vitamin D in insulin resistance. J Biomed Biotechnol. 2012; 2012:634195. https://doi.org/10.1155/2012/634195.

Benetti E, Mastrocola R, Chiazza F, Nigro D, D'Antona G, Bordano V, et al. Effects of vitamin D on insulin resistance and myosteatosis in diet-induced obese mice. PLoS One. 2018; 13(1):e0189707. https://doi.org/10.1371/journal.pone.0189707.

Ali R, Fawzy I, Mohsen I, Settin A. Evaluation of vitamin D receptor gene polymorphisms (Fok-I and Bsm-I) in T1DM Saudi children. J Clin Lab Anal. 2018; 32(5):e22397. https://doi.org/10.1002/jcla.22397.

Yang CY, Leung PS, Adamopoulos IE, Gershwin ME. The implication of vitamin D and autoimmunity: a comprehensive review. Clin Rev Allergy Immunol. 2013; 45(2):217–26. https://doi.org/10.1007/s12016-013-8361-3.

Abd-Allah SH, Pasha HF, Hagrass HA, Alghobashy AA. Vitamin D status and vitamin D receptor gene polymorphisms and susceptibility to type 1 diabetes in Egyptian children. Gene 2014; 536(2):430–4. https://doi.org/10.1016/j.gene.2013.12.032.

Sahin OA, Goksen D, Ozpinar A, Serdar M, Onay H. Association of vitamin D receptor polymorphisms and type 1 diabetes susceptibility in children: a meta-analysis. Endocr Connect. 2017; 6(3):159–71. https://doi.org/10.1530/EC-16-0110.

Al-Agha AE, Ahmad IA. Association among vitamin D deficiency, type 1 diabetes mellitus and glycemic control. J Diabetes Metab. 2015; 6(594). https://doi.org/10.4172/2155-6156.1000594.

Savastio S, Cadario F, Genoni G, Bellomo G, Bagnati M, Secco G, et al. Vitamin D deficiency and glycemic status in children and adolescents with type 1 diabetes mellitus. PloS One. 2016; 11(9):e0162554. https://doi.org/10.1371/journal.pone.0162554.

Elsayed AM, Mohamed GA. Vitamin D deficiency and its correlation to hemoglobin A1C in adolescent and young adult type 1 diabetes mellitus patients. AAMJ. 2016; 14(2):76–80. https://doi.org/10.4103/1687-1693.192643.

Shin YH, Shin HJ, Lee YJ. Vitamin D status and childhood health. Korean J Pediatr. 2013;56(10):417–23. https://doi.org/10.3345/kjp.2013.56.10.417.

Martin T, Campbell RK. Vitamin D and diabetes. Diabetes Spectr. 2011; 24(2):113–8.

Kliegman RM. Nelson Textbook of Pediatrics. 20thed. Philadelphia: Elsevier; 2016. P. 2777.

American Diabetes A. 2. Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes-2018. Diabetes Care 2018; 41(Suppl 1):S13–27. https://doi.org/10.2337/dc16-er09.

Centers for Disease Control and Prevention, National Center for Health Statistics. CDC growth charts: United States. http://www.cdc.gov/growthcharts/. Accessed 30 May 2020.

Bergenstal RM. Glycemic variability and diabetes complications: does it matter? Simply put, there are better glycemic markers! Diabetes Care. 2015; 38:1615–21. https://doi.org/10.2337/dc15-0099.

Aljabri KS, Bokhari SA, Khan MJ. Glycemic changes after vitamin D supplementation in patients with type 1 diabetes mellitus and vitamin D deficiency. Ann Saudi Med. 2010; 30(6):454–8. https://doi.org/10.4103/0256-4947.72265.

Mutlu A, Mutlu GY, Özsu E, Çizmecioğlu FM, Hatun Ş. Vitamin D deficiency in children and adolescents with type 1 diabetes. J Clin Res Pediatr Endocrinol. 2011; 3(4):179–83. https://doi.org/10.4274/jcrpe.430.

Omar M, Nouh F, Younis M, Younis M, Nabil N, Saad M, et al. Culture, Sun Exposure and Vitamin D Deficiency in Benghazi Libya. J Adv Med Med Res. 2018; 25(5):1–13. https://doi.org/10.9734/JAMMR/2018/39562.

Nansel TR, Lipsky LM, Iannotti RJ. Cross-sectional and longitudinal relationships of body mass index with glycemic control in children and adolescents with type 1 diabetes mellitus. Diabetes Res Clin. 2013; 100(1):126–32. https://doi.org/10.1016/j.diabres.2012.12.025.

Mohammadian S, Fatahi N, Zaeri H, Vakili MA. Effect of vitamin D3 supplement in glycemic control of pediatrics with type 1 diabetes mellitus and vitamin d deficiency. JCDR. 2015; 9(3):SC05. https://doi.org/10.7860/JCDR/2015/10053.5683.

El Baba K, Zantout MS, Akel R, Azar ST. Seasonal variation of vitamin D and HbA(1c) levels in patients with type 1 diabetes mellitus in the Middle East. Int J Gen Med. 2011; 4:635–8. https://doi.org/10.2147/IJGM.S23548.

Kavadar G, Demircioğlu DT, Özgönenel L, Emre TY. The relationship between vitamin D status, physical activity and insulin resistance in overweight and obese subjects. Bosn J Basic Med Sci. 2015; 15(2):62–6. https://doi.org/10.17305/bjbms.2015.399.

Karnchanasorn R, Ou HY, Chiu KC. Plasma 25-hydroxyvitamin D levels are favorably associated with β-cell function. Pancreas. 2012; 41(6):863–8. https://doi.org/10.1097/MPA.0b013e31823c947c.

How to Cite
Ahmed, M., & Chalabi, D. (2021). Effect of vitamin D supplementation on HbA1c level in a cohort of type 1 diabetic patients. Zanco Journal of Medical Sciences (Zanco J Med Sci), 25(3), 649-656. https://doi.org/10.15218/zjms.2021.031
Original Articles