The vitamin D deficiency (25OHD) is very common and affects about 80% of the population of French osteoporotic women over 50 years [5]. It contributes significantly to bone fragility and consequently the risk of fracture. To remedy this deficit, it is necessary to provide a suitable and sustainable supplementation. Changes in vitamin D deficiency ranging from undetectable to a 25OHD value very close to 30ng / ml lead to differences in therapeutic regimens, specific to each clinician in the absence of precise data in the literature. No consensus on supplementation dosages and methods have been proposed so far. Also, given the frequency of vitamin D deficiency including osteoporosis observed in the population, it became necessary to establish a single, uniform regimen for all patients with osteoporosis

Inclusion Criteria:

• Postmenopausal women ≥ 50 years
• Osteoporosis with BMD T-score ≤ -2.7DS -2.5DS to at least one of the two main sites analyzed, with or without fracture
• having signed an informed consent

Exclusion Criteria:

• Taking a "loading dose" of vitamin D in the last six months (a daily intake in combination with calcium will not be a cause of exclusion but should be discontinued during the study).
• Taking an osteoporosis treatment combined with vitamin D in the same tablet (or Adrovance Fosavance * *)
• Treatment with thiazide diuretic
• Known malabsorption (celiac disease)
• Scalable Endocrine disorders: hyperthyroidism, hyperparathyroidism, hypoparathyroidism.
• Persistent or nephrolithiasis occurred in the previous 5 years
• known sarcoidosis
• Persons under guardianship or trusteeship
• Hypercalcemia and hypercalciuria
• 25OH vitamin D levels> 50ng / ml