So far I haven’t had much success with vitamins or other supplements.
I did a test for vitamin B12 deficiency when I was thinking of trying supplements, but my levels were well within the normal range and I was told that supplementing vitamins doesn’t help unless one is in fact deficient. Having too much vitamin B can actually be a problem, so having one’s level checked and only supplementing if needed, might be a good idea.
I was rather severely deficient on vitamin D, so I am supplementing that and it has affected my mood positively but I don’t think it made any other differences. Vitamin D deficiency is pretty unhealthy, so I am sticking to the supplementation.
I am taking fish oil, specifically EPA, and have been for more than a year, but didn’t see much of an effect. (It is generally seen as harmless, might be good for the heart, etc. so I am sticking to it anyway. ) Some research says that the dose needs to be above 1000 mg per day to be effective (which is about three times as high as the recommendation on the package). Might try that, but not sure, yet.
Another supplement that I have tried was SAMe. In terms of mood, this worked almost as well as the antidepressant that I took a couple of years ago and it started working much faster, but I think the benefits for improving focus are somewhat limited and science is still on the fence about whether SAMe has positive effects for ADHD or not. There have been a few positive and a few inconclusive studies, so probably there isn’t much of an effect. I’ve stopped taking it, because the recommendation was to only take it for a couple of months after feeling better.
I recently read (… well, started reading… ^^ ) a book “Getting Ahead of ADHD: What Next-Generation Science Says about Treatments That Work”. It might be worth looking at, if you are interested in supplements and alternative treatments.