Serum 25(OH) D in Diabetes Mellitus Type 2: Relation to Glycaemic Control

There is increasing evidence on association between vitamin D insufficiency and diabetes, but the impact of vitamin D status on glycaemic status and vice versa, has not been well reported. Our aim was to investigate the level of 25-hydroxyvitamin D(25(OH)D) and the prevalence of vitamin D abnormalities in patients with diabetes mellitus (DM) type2 and in those without diabetes; and to ascertain the impact of 25(OH)D levels on glycaemic control and vice versa.

Serum 25(OH) D was determined in 337 Kurd patients with DM type2 and in 146 patients without DM type2. Its correlation with the marker of glycaemic control (HbA1c) as well as with anthropometric parameters (age, gender, and body mass index), diabetes duration, and serum blood glucose was examined.

The mean ± SD values for serum 25hydroxy (OH) D levels of diabetic patients was 25.6± 12.6 ng/ml and those for the controls was 34.1±14.7 ng/ml (p<0.01). The prevalence of vitamin D insufficiency was significantly higher among diabetic patients than among the controls (53.7% vs. 29.4%, p<0.001). This finding was still true even after the means of serum 25 (OH) D levels were adjusted to those of severe vitamin D deficiency (4.4% vs. 0.68%).Patients with poor glycaemic control had a higher prevalence of low vitamin D status (90%) than those with sufficient vitamin D levels (76%). As compared to diabetics with a good and fair glycaemic control, diabetics with a poor glycaemic control exhibited lower 25(OH)D levels (p<0.01) and a higher prevalence of low vitamin D status (89% vs. 4% and 7%) respectively. Patients with a diabetes duration of more than 5 years also had a higher prevalence of low vitamin D status as compared to vitamin D sufficient group (51% vs. 40%). A statistically negative significant correlation between serum 25 (OH) D levels and HbA1c % was found in diabetic patients (r=0.238, p<0.01).

A low vitamin D status is present in two thirds of patients with DM type 2, particularly among diabetics with poor glycaemic control and among those with longer diabetes durations. This may reflect the additive effect of glycaemic control on vitamin D status.