Vitamin B-12, a nutrient found in animal products such as meat, seafood, poultry, eggs and dairy, plays a crucial role in metabolism, DNA synthesis and neurological function. Inadequate intake or absorption of vitamin B-12 can cause vitamin B-12 deficiency. If you have signs of this deficiency, you may need a blood test to determine B-12 levels in your blood.
Doctors typically draw blood to test vitamin B-12 levels. Patients should not eat or drink for about six to eight hours before the test, according to Medline Plus, a National Institutes of Health online medical encyclopedia. Certain medications may affect the test results, so discuss all medications you are taking with your doctor.
Normal B-12 Levels
Doctors in the United States measure vitamin B-12 levels in picograms per milliliter, or pg/ml. Normal B-12 levels typically fall between 200 and 900 pg/ml, according to Medline Plus. Normal values may vary depending on the laboratory, however, so discuss your test results with your doctor.
Vitamin B-12 levels below 250 pg/ml may indicate a B-12 deficiency in adults, according to the National Institutes of Health Office of Dietary Supplements. Values below 170 pg/ml indicate a deficiency in most people, and values between 200 and 500 pg/ml may indicate a deficiency in older adults. Because excess vitamin B-12 leaves the body in urine, high levels of B-12 are rare, according to Medline Plus.
B-12 Deficiency Symptoms
Common symptoms of vitamin B-12 deficiency include fatigue, weakness, shortness of breath, dizziness, difficulty concentrating, loss of appetite, weight loss, pale skin and sore or inflamed tongue. Prolonged vitamin B-12 deficiency may cause serious neurological symptoms, such as confusion, memory loss, difficulty maintaining balance, depression and dementia.