Hello thanks for asking from HCM for your health related queries I can understand your concern. There are no clearcut guidelines for use of Creatine supplements while on Lithium Carbonate therapy. Creatine metabolism requires renal clearance and Lithium is also excreted from kidneys. Taking both these together can result in pressure on kidneys and this may result in impaired metabolism and some times Lithium toxicity gets precipitated so in my opinion use of any protein supplement should be avoided while on Lithium therapy. Lithium also reduces the metabolism of Creatine and this also cause improper metabolism of creatine this would reduce the efficacy of supplements. So if the supplements are not very necessary I would advise you to stop using both these together. Consult your doctor for detailed advise. Thanks, Hope this helps you. Take care.