Background Plasma concentrations of human chorionic gonadotropin (hCG) have been shown to increase with age due to pituitary secretion. We previously recommended that an hCG cutoff of 14.0 IU/L be used for women ≥ 55 years of age. However, it remains unknown whether concentrations > 14.0 IU/L can be expected in women with advanced age. Our objectives were to establish plasma hCG reference intervals and correlate follicle stimulating hormone (FSH) and hCG concentrations in postmenopausal females ≥ 55 years. Methods Residual plasma samples from 798 women ≥ 55 years were utilized with 303, 269, and 226 samples belonging to the age groups 55–69, 70–84, and ≥ 85 years, respectively. FSH and hCG were measured using the Abbott ARCHITECT. All positive hCG samples (hCG ≥ 5 IU/L) were analyzed for potential heterophile antibody interference and 3 were excluded. Electronic medical records were reviewed and patients with malignancy were excluded. Results 8% (56/666) of women age ≥ 55 years had plasma hCG ≥ 5 IU/L. There were 19, 16, and 21 patients with hCG ≥ 5 IU/L in the age groups 55–69, 70–84, and ≥ 85 years, respectively. The highest hCG concentrations observed in each age group were: 55–69 years maximum = 11.7 IU/L and 97.5th percentile = 9.6 IU/L; 70–84 years maximum = 18.09 IU/L, 97.5th percentile = 6.2 IU/L; ≥ 85 years maximum = 11.1 IU/L and 97.5th percentile = 10.0 IU/L, and the overall 97.5th percentile = 8.5 IU/L for all women ≥ 55 years of age. Neither hCG nor FSH concentrations continued to increase with age in women ≥ 55 years. Conclusions The prevalence of positive hCG in women ≥ 55 years is 8%. This study confirms our previously recommended cutoff of 14 IU/L for women ≥ 55 years of age. In women ≥ 55 years of age, FSH concentrations do not predict hCG concentrations.