Most experts say up to 500 mg per day for a couple of months is generally well tolerated.
Ansardi DC, Porter DC, Morrow CD (1992) Myristylation of poliovirus capsid precursor P1 is required for assembly of subviral particles
In one 26-month randomized controlled trial, 170 women younger than 35 years took clomiphene citrate ("Clomid") and either 3 g/day supplemental L-carnitine or placebo from day 3 of their menstrual cycle until the day of their first positive pregnancy test result
Five metabolites (betaine, L-acetylcarnitine, L-carnitine, ribonic acid, and glucaric acid) increased and three metabolites (uridine, taurine, and glutathione) significantly decreased in the aqueous humor of glaucoma patients (Fig
Muftuoglu M, Li L, Basyal M, Ayoub E, Lv J, Bedoy A, Patsilevas T, Bidikian A, IssaGC, Andreeff M
"A standardized Withania somnifera extract significantly reduces stress-related parameters in chronically stressed humans: a double-blind, randomized, placebo-controlled study." JANA 11 (2008): 50-56