Abstract: Objective: To observe the influence of lithium carbonate on thyroid radioactive iodine uptake(RAIU) and to investigate the effects of the therapy of lithium carbonate plus radioiodine on low thyroid iodine uptake in Graves's patients.Methods: Thirty-six hyperthyroidism patients with RAIU<50% were orally administered lithium carbonate 0.25 g,3 times per day for 7 days.The thyroid RAIU rate was detected before and after treatment,and the dosages of ¹³¹I needed by the patients were varied in accordance with the RAIU rate.Results: After lithium carbonate therapy,the thyroid RAIU in 36 cases increased from(45.58±4.01)% to(64.36±4.66)% and the dosage of ¹³¹I needed by patients decreased from(991.6±577.2) MBq to(503.2±288.6) MBq.The difference was significant(P<0.001).Conclusions: Lithium carbonate can increase the thyroid RAIU in Graves'patients,which enables the patients with low thyroid RAIU to receive ¹³¹I therapy;and the dosage of ¹³¹I is also decreased to some degree.