Vitamin B6 is a water-soluble vitamin in the B complex group. It is an important component of enzymatic reactions throughout the body, including the use of amino acids, glucose production and metabolism of fats. This vitamin can be found in meats, fish, green vegetables, nuts, beans and whole grains. Some people don't get enough vitamin B6, either through a poor diet or because of medical conditions that make it harder for the body to absorb this nutrient. Heavy food processing can destroy the vitamin B6 naturally present in many foods, making people who eat a lot of processed food susceptible to deficiencies.

Doctors usually recommend a vitamin B6 blood test for people who suffer from skin inflammation or a scaly rash accompanied by prickling or numbness in the hands and feet. In some people, the tongue becomes red and sore and the corners of the mouth crack. Depression and irritability are common in people who don't have enough vitamin B6. This vitamin is also needed for the formation of blood cells and low levels may cause anemia or weakness.

Like other blood tests for B vitamin levels, a vitamin B6 test is most accurate if it is performed after 10 hours of FASTING. Patients should avoid all food and beverages other than water. If the test shows low levels of vitamin B, patients can improve their nutrition by consuming more whole grains and unprocessed foods or by using supplements.