A homocysteine test is ordered to determine if a person has vitamin B12 or folic acid deficiency. The test is also prescribed for individuals with malnourished individuals or the elderly whose body absorb less vitamin B12 from their diet. This test also helps identify for a rare inherited disease (hypocynthuria) which causes a deficiency of one of the several enzymes required to convert food into energy. It also helps identify several unexplainable blood clots leading to cardiovascular diseases. The symptoms related to this deficiency are very subtle initially like diarrhea, fatigue, weakness, loss of appetite, tingling, numbness and/or burning of feet, arms, and legs.