What are the risks of low vitamin D levels in the blood?

Vitamin D deficiency, or low levels of vitamin D in the blood, can cause bone pain and muscle weakness, states WebMD. Vitamin D is essential for strong bones.

Low levels of vitamin D in the blood have been associated with increased risk of death from cardiovascular disease, cognitive impairment in older adults, severe asthma in children and cancer, according to WebMD. Research suggests that vitamin D may play a role in the prevention of diabetes mellitus, hypertension and multiple sclerosis. A level of 20 to 50 nanograms per milliliter of vitamin D in the blood is considered adequate, and less than 12 nanograms per milliliter indicates vitamin D deficiency.