Vitamin D and B12 Combo Test

The major form of vitamin D found and measured in your blood is 25-hydroxyvitamin D. It is relatively inactive but is the precursor to the active hormone. Vitamin D is also known as the ‘sunshine vitamin’ as most of the vitamin that the body requires is produced through the skin’s exposure to the sun. Vitamin D also comes from the food however it can be difficult to get all that the body requires from just the diet.

Vitamin B12, also known as cobalamin, is an essential vitamin and must therefore be taken in through the diet. It is found predominantly in meat, fish, eggs and dairy products; therefore vegetarians and vegans are at greater risk of low B12 levels, though it can be found in very small quantity in certain algae.

Vitamin B12 is bound to the protein in food and is released during digestion by the stomach acid. When released from the protein a substance called intrinsic factor combines with it to enable absorption into the bloodstream. An autoimmune condition called pernicious anaemia prevents absorption by preventing the production of intrinsic factor; this is a leading cause of vitamin B12 deficiency. Other conditions affecting the stomach or small intestine such as coeliac disease, Crohn’s disease and ulcerative colitis can also lead to inadequate B12 absorption.