ALCAR doesnt sit right with some people, especially those with any form of hypothyroidism, mild or not. I think the Carnitine part of the molecule prevents Thyroid hormones from entering their target cells. Whenever I take ALCAR I experienced puffy, heavy eyelids and an uncomfortable depression with some irritability. I become very introverted as well. My eyes get slightly red and honestly its similar to being mildly stoned but in the worst way possible. Puffy eyelids can be a symptom of a thyroid issue. I use NAC (N-Acetyl-Cysteine) as an Acetyl- donor alternative.
http://www.ncbi.nlm....pubmed/15591013
"In particular, L-carnitine inhibits both triiodothyronine (T3) and thyroxine (T4) entry into the cell nuclei. In the randomized trial, we showed that 2 and 4 grams per day of oral L-carnitine are capable of reversing hyperthyroid symptoms (and biochemical changes in the hyperthyroid direction) as well as preventing (or minimizing) the appearance of hyperthyroid symptoms (or biochemical changes in the hyperthyroid direction)."
Hyperthyroid patients use Carnitine to effectively treat their condition. I think that says a lot. You may not have diagnosed Hashimoto's disease but I think it is important to support general thyroid health. So it might not be so healthy to supplement with high doses of ALCAR everyday like some people do, since it may be suppressing the necessary function of your thyroid. Try NAC!