Dear user! There are various side-effects of Lithium like nausea, diarrhea, muscle weakness, fatigue, dizziness, etc. which usually get better with time as one is on the medication. It s not known to have any side effect related to body temperature alteration when in sun or heat exposed areas. Dose adjustment is important while one is on Lithium therapy due to it s narrow therapeutic index (the narrowness in the range of its dose used for treatment and the dose that may cause toxic or harmful side-effects). One should stick to the advised dose and frequency and shouldn t hesistate to see the doctor if there is any obvious side effect. While other factors may also cause symptoms of cold and clammyness and diarrhea and one should make sure that diet and hydration is rightly achieved. Wishing the best! Do feel free to write back!