Randomized double-blind placebo-controlled clinical trial. Consists of the administration of 5,000 IU of vitamin D3 vs Placebo in patients with gestational diabetes mellitus during eight weeks. The objective is to analyze the effects of the intervention on the biochemical parameters that are part of the glycemic profile (insuline, HBA1c, glucose)

Two groups of patients diagnosed with gestational diabetes mellitus. Once the selection criteria are verified, they will be assigned randomly in one of the two arms,one of them will recive 5,000 IU of vitamin D and the other one placebo (talcum food grade). Baseline measurements of vitamin D, glucose,insulin, HBA1c, calcium, phosphorus. At the end of the eight weeks will be determined again the aforementioned biochemical parameters.

Inclusion Criteria: Patients with a single pregnancy.

• Patients diagnosed with GDM, which were diagnosed by a glucose tolerance curve 100 grams of glucose, with two altered results from the following: fasting> 95 miligrams / deciliter, 1 hour> 180miligrams / deciliter, 2 hour> 155miligrams / deciliter, 3hous> 140 miligrams / deciliter.
• Gestational age between 24 -30 weeks confirmed with ultrasound of the 1st or 2nd trimester
• Age between 18 and 40 years.

Exclusion Criteria: Patients with pre-existing diabetes mellitus

• Patients with predictive factors for vitamin D hypovitaminosis such as: use of anticonvulsants, renal disease, glomerular filtration rate <60milliliters / minute, thyroid disease or any other pre-existing endocrinological disorders.
• Hypercalciuria> 300 miligrams / day
• Patients taking vitamin D supplementation during the 6 months prior to the study (does not include polyvitamins with lower vitamin D concentrations <500 IU)
• Active and passive smoking patients.

The capsules with vitamin D or placebo have the same organoleptic characteristics. The jars and envelopes that contain them are identical. The envelopes are identified by a code that only knows who will analyze the data