You need to correct any methylation problems you have in order to properly correct your homocysteine (HCY) levels. Without knowing your histamine levels or how your body methylates (over-methylates or under-methylates) you can't know what form of niacin to take.

One simple test you can do yourself is to get some nicotinic acid in a 50 mg. dose. Nicotinic acid is the flush producing niacin. If you have a flush from one dose of 50 mg. of nicotinic acid (taken on any empty stomach) then you have histamine levels. I would be inclined to think you may not have high histamine levels, but that is just a guess.

A low histamine person would probably require a dose of about 250 mg. of nicotinic acid to have that flush. If no flush from 50 mg. of nicotinic acid then you might try 100 mg. dose to double check this. If that doesn't work you might try once more a total of 200 mg. or 250 mg. of nicotinic acid just to make sure that you do in fact have low histamine levels and that supplement is the kind to cause a flush.

Methylation is important and this is how you get your HCY levels back in line. Even if you HCY levels are good you should not ignore nutrition for proper methylation. But if you take vitamin b6 then you should also take some form of niacin too. The only way to know what form of niacin is best for you is to either have your histamine levels checked with a blood test or try the flush and see what dose will cause a flush for you. Niacin is needed along with glutamine to make NAD. This is more of an explanation of NAD.

Niacinamide-adenine dinucleotide (NAD) is an active enzyme that is required for the proper function of vital areas of the brain. In schizophrenia, there appears to be a failure to deliver enough NAD to the brain. Vitamin b3 is required for the transformation of tryptophan, an amino acid, into NAD. If there is a niacin deficiency, this necessary transformation of trypotphan into NAD is inhibited, and there is not only a NAD deficiency established, but there is also an overload of tryptophan in the brain’s chemistry. Tryptophan is considered to be one of the most toxic of amino acids. An overload of it in the brain can be very harmful, especially if it is not properly converted into NAD, because it can cause undesirable perceptual and mood changes. If there is a b3 deficiency, for whatever reason, the consequent NAD deficiency will lead to ever-increasing tryptophan overload uninterruptedly unless and until the proper levels of b3 are given.

Source: Brain Allergies: The Psychonutrient Connection by William H. Philpott, MD and Dwight K. Kalita, Ph.D.

Taking high doses of nutritonal supplements is how you correct any king of nutritional deficiencies you may have. But taking high doses of nutrtional supplements is a lot like taking drugs and should only be done with the proper medical supervision. Sometimes people try some supplements which may not make them feel any better, and that is not because they don't have deficiencies but they are not taking either the proper doses or the proper combo of nutrients. If you miss just one nutrient in this process you can end up causing a whole net set of symptoms. You really need to work with a qualified doctor who has experience with treating nutritional deficiencies. I happen to think that orthomolecular training is great but not many doctors have this kind of background. It is not easy to find someone who knows how to treat nutritional deficiencies.

The internet may have a wealth of information, but sometimes you also have to do research with other sources, like books, articles, forums, etc. But, the right doctor is absolutely critical to this process.