BACKGROUND: Hyperprolactinemia is an endocrine disorder characterized by abnormally elevated levels of prolactin (PRL) in the serum. Macroprolactinemia refers to the condition where more than 60% of the prolactin circulating in the peripheral blood is composed of high molecular weight macroprolactins. These macroprolactins typically have low biological activity but can lead to a false increase in serum prolactin levels. METHODS: We report a case of pseudoelevation of prolactin caused by macroprolactin. We used pituitary MRI and other examinations to identify the cause of elevated serum prolactin levels and different detection platforms and polyethylene glycol (PEG) precipitation method to screen for the possibility of pseudo elevation of prolactin caused by macroprolactin. RESULTS: Whether measured using two different testing platforms or using our own testing platform after sample pretreatment with PEG, serum prolactin levels were within the normal range. Therefore, based on the negative results of pituitary MRI, we believe that the patient's pseudo elevation of serum prolactin is caused by interference from macroprolactin. CONCLUSIONS: When there is an abnormal increase in serum prolactin but no evidence of related clinical symptoms, staff should consider the possibility of macroprolactin interfering with prolactin testing, take corresponding corrective measures, and avoid unnecessary examinations and treatments for patients.