When taking care of patients, it is not usual to request blood levels of vitamins in the body with the exception of Vitamin B12, vitamin D and folic acid. Testing for the levels of vitamins in the body is time consuming and expensive (with the exception of those mentioned) and not standardised i.e. it is unclear what correlates best with the deficiency state - blood levels, serum levels, levels in various cells or in tissues. Vitamin deficiency syndromes are quite distinctive and allow the physician to determine which vitamin is deficient. Giving the vitamin supplementation rapidly reverses the symptoms and the findings the patient may have and this provides indirect evidence of vitamin deficiency.