There are no specific laboratory tests or reference values for vitamin B6 used to identify a deficiency, reports the Merck Manual for medical professionals. However, serum levels of pyridoxal phosphate can be used to diagnose a suspected deficiency of vitamin B6.
Because a deficiency of vitamin B6 is difficult to identify through a laboratory test, most diagnoses are clinically based, reports the Merck Manual. Infants who exhibit seizures are commonly identified as having a vitamin B6 deficiency, especially those who seizure after administration of anticonvulsants. Adults with a vitamin B6 deficiency may also experience seizures after anticonvulsant medication. Individuals with a deficiency in any of the B vitamins are likely to be deficient in B6 as well. Alcoholism and issues with protein-energy nutrition are additional signs that physicians look for to identify a deficiency.
Individuals who suffer from a vitamin B6 deficiency often experience pellagra-like symptoms, according to the Merck Manual. Weakness or numbness in the hands and feet are common symptoms, as are swelling of the tongue and cracking of the lips. Scaly, yellowed skin without inflammation is characteristic of a deficiency in B6. Abnormal brain activities are recorded in some adults with a B6 deficiency, and they may also suffer from depression or confusion because of the deficiency. This deficiency in adults is commonly treated with 50 to 100 mg of pyridoxine.