Objective: There is evidence that measuring levels of endocrine hormones, lactate and Simplified Acute Physiology Score II (SAPSII), can predict the prognosis and length of hospitalization of a poisoned patient. This study was conducted to evaluated levels of TSH hormone and serum lactate among poisoned patients admitted to the ICU during one year. Methods: In this cross-sectional study, patients who were admitted to the Toxicology ICU were non-randomly enrolled in the study after consent forms were obtained from the closest relatives. After sampling, serum levels of TSH and lactate was measured using similar kits. Data were analyzed by SPSS software (version 21). Results in this descriptive cross-sectional study, total of 150 patients with an average age of 39 years were examined, and 26 patients died. Simplified Acute Physiology Score II (SAPSII) and lactate were identified as prognostic factors for disease outcome. Moreover, after adjusting age and gender using Logistic Regression analysis, chance of death among patients was increased by 10% with the addition of each one score to Simplified Acute Physiology Score II (SAPSII) (P value <0.01). Conclusion: Upon admission, serum lactate and Simplified Acute Physiology Score II (SAPSII) scoring system can help predict the outcome of poisoning in poisoned patients and play an important role in treatment and isolation of high risk patients. However, TSH cannot be considered as a prognostic factor. Further studies are recommended to certainly approve this conclusion Serum Lactate, TSH, Poisoning, ICU, prognosis.