Vitamin D is composed of a group of fat-soluble secosteroids. Two of the important forms are D2 and D3. Vitamin D3 is formed in your skin after you are exposed to UV rays from the sun or from artificial sources. It can also be found in many types of food. Vitamin D in general can be found in mushrooms, eggs, and fatty fish such as sardines, tuna, mackerel, and salmon.

There are many Vitamin D deficiency symptoms. A lack of Vitamin D will lead to several dangerous symptoms, particularly those which are related to the bones.

Avoiding the sun would lead to a low blood calcidiol which impairs bone mineralization. This in turn softens the bone and would lead to Rickets. This is a childhood disease wherein the bones will not form properly and become fragile. There would be impeded growth along with deformity. Another disease would be Osteomalacia, which thins the bones and affects adults. The bones will be fragile and there is proximal muscle weakness. You would feel chronic musculoskeletal pain.

There are vitamin D deficiency symptoms that are said to occur in women, particularly, such as depressive behavior, being moody especially during the premenstrual stage, and seasonal affective disorders. Menopausal women who do not have adequate vitamin D intake would have osteoporosis.

For children, the symptoms would be low calcium levels in the blood, fragile bones and skull, breathing difficulties and muscle cramps. Breast milk does not have adequate Vitamin D and one way to prevent abnormality is to expose the infant to delicate sunlight, ideally around 6 to 6:15 in the early morning.

Being overweight makes it difficult for one to absorb Vitamin D. Those who have dark skin might be at risk as well, because melanin inhibits the skin from getting enough sunlight that promotes vitamin D absorption. This may lead to various vitamin D deficiency symptoms.

An overdose of Vitamin D such as taking in 1250 mg a day or 50,000 IU for healthy adults will lead to toxicity in a matter of months. It is very important for pregnant and breastfeeding women to consult a doctor before taking in any supplements that contain vitamin D because these may lead to fetal sensitivity and maternal hypercalcaemia. These will in turn lead to mental retardation together with facial deformities.