Background/ Objectives: Vitamin D deficiency has been found to be associated with glycated hemoglobin (HbA1c) levels amongst

patients with diabetes mellitus type 2 (DM2). However, the beneficial effect of vitamin D supplementation on HbA1c levels in DM2

patients has been investigated and its role remains controversial. The purpose of this study was to examine the role of vitamin D

supplementation on HbA1c levels amongst Libyan patients suffering from DM2.

Methods and design: Ninety-seven DM2 patients of both genders (M = 51) (F = 46), with an age range of 26-59 years, were recruited

from the Al-Wafi Medical Laboratory in Tripoli, Libya. All patients were informed about the nature of the study and oral consent was

obtained from all patients. Weight and height were measured, and dietary and lifestyle information was obtained. Blood samples were

collected and HbA1c and vitamin D levels were measured pre-and post-the administration of vitamin D supplementation for three

months. The participants were divided into three groups according to HbA1c level, and then into four groups, based on their vitamin

D serum levels. The relationship between vitamin D and HbA1c was investigated.

Results: Vitamin D levels have increased after the administration of vitamin D supplementation amongst DM2 patients. We noticed

that the level of HbA1c also decreased from 6.97% at the baseline to 5.65% after supplementation of vitamin D. The results showed

that the difference in HbA1c levels was significant after administration of vitamin D as a supplement (P-value = 0.000). The level of

vitamin D increased from 8.34±2.59 to 39.95±2.85 ng/ml after the administration of the supplements. In mixed ANOVA analysis, the

present study confirmed that the relationship between HbA1c and the factors measured appear to be weak and these findings indicate

that HbA1c was not influenced by all these factors studied.

Conclusions: The results of this study have shown that vitamin D supplementation significantly reduced the level of HbA1c amongst

patients suffering from DM2. These results may be beneficial for the overall health and blood glucose control of those patients.