Scottish Trace Element and Micronutrient Reference Laboratory

Scotland's specialised laboratory for trace elements and vitamins in health and disease

Vitamin B6

Trace Elements

Vitamins

Specialised services

The main circulating forms of vitamin B6 are pyridoxal phosphate (PLP), pyridoxal (PL), and pyridoxic acid (PA). The active form in the body is PLP. It acts as a coenzyme for many enzymes in the body and is involved in metabolism of proteins, carbohydrates, and fats, production of serotonin and haem, and binding of steroid hormones to their receptors.

Deficiency is associated with various symptoms: irritability, depression, and confusion, inflammation of the tongue and sores or ulcers of the mouth.

PLP is a cofactor in homocysteine metabolism and aids in the metabolism of homocysteine to cysteine so lowering its impact on cardiovascular disease. Vitamin B6 has been widely used as a treatment of premenstrual tension although the evidence supporting its use is weak. Chronically high concentrations of vitamin B6 can be toxic resulting in peripheral neuropathy.

Vitamin B6 is measured in red blood cells as pyridoxyl phosphate. Vitamin B6 is almost entirely bound to albumin and so plasma levels fall during the acute phase response; this is not the case when vitamin B6 is measured in red blood cells. (Analysis of vitamin B6 in plasma is available in exceptional circumstances.)

Sample Requirements and Reference Values