Lithium, widely used for the treatment of mania, has adverse side effects on circadian rhythms of pineal and testicular hormones. Objective was to examine the role of lithium on circadian rhythms of other hormones and glucose profiles in light-dark (12L:12D), constant light (12L:12L) and constant dark (12D:12D) regimens in rats. Intraperitoneal injection of lithium (2 mEq/kg body wt daily for 15 days) sustained circadian rhythms of T3, T4, thyroid-stimulating hormone (TSH), corticosterone, norepinephrine and epinephrine in light-dark and constant dark but not in constant light. But it abolished circadian rhythms of insulin and blood glucose in all the photoperiodic regimens, except insulin, without changing their pattern in constant dark. Patterns of circadian rhythms of thyroid and TSH, and adrenal hormones remained unchanged after lithium treatment in L-D or D-D, except TSH in L-D. The probable role of photoperiodic cue and lithium on circadian and/or nycthemeral (daily) rhythms of hormones and blood glucose profiles is discussed. © 2012 Taylor & Francis.