Screening for elevated homocysteine levels is recommended for individuals who manifest coronary artery disease that is out of proportion to their traditional risk factors or who have a family history of premature atherosclerotic disease. Blood for measuring serum homocysteine levels is drawn after a 12-hour fast. Levels between 5 and 15 micromoles per liter are considered normal. Levels above 10 warrant treatment. The effect of supplementation is usually apparent within a month.
Medical supervision is advisable to be certain that the corrective process is done properly.
Some doctors routinely recommend that patients known to have atherosclerosis take B-vitamin supplements without being tested to determine whether their homocysteine level is elevated. They reason that since supplementation is harmless and since elevated homocystine levels might be a factor, testing is not worth bothering with.