Background: Recent studies suggest that glycemic variability could influence the
risk of complications in type 1 diabetes mellitus (T1DM). There are no data about the action
of vitamin D (VD) on glycemic variability. Our pilot study aims to evaluate glycemic variability
and insulin needs in patients with T1DM supplemented with VD.
Methods: 22 patients received doses of 4000 and 10000 IU/day of cholecalciferol for 12
weeks, according to the patient’s baseline VD levels and underwent continuous glucose
Results: Correlations were found between percentage variation (Δ) of glycemia standard deviation
(ΔSDG), calculated using continuous glucose monitoring, with Δ of basal (r= 0.6; p
<0.01) and total insulin dose (r= 0.6; p <0.01). Correlations between VD status after supplementation
and Δ of prandial (r = 0.5; p <0.05) and total insulin dose (r = 0.4; p <0.05) were
found, suggesting that the dose of insulin needed by patients is lower when VD status is better.
We divided patients in two subgroups: SDG improved (subgroup 1; n =12 (55%)) and
SDG worsened (subgroup 2; n =10 (45%)). Group 1, compared to subgroup 2, required a
lower insulin dose (Δbasal insulin dose = -8.0 vs. 6.3%; p <0.05) and had a lower frequency
of hypoglycemia (27% vs. 64%, hypoglycemias/days evaluated; p <0.01).
Conclusions: Our study suggests a relation between VD supplementation, improved glycemic
variability, lower insulin needs and lower frequency of hypoglycemia in patients with