From 1928 to 1961, Man worked as a researcher, and technician, and then a professor at Yale. She worked at a lab at Yale with John P. Peters and Herman Yannet where they developed the first test to detect hormone levels in the thyroid gland. The test was called Butanol-Extractable Iodine (BEI) test. In 1961, Man continued her research at Brown University, where she discovered infants with low hormone levels in the thyroid gland later developed a cognitive disability as children. Man advocated for infants to get their thyroid hormone levels tested. Man also studied the effects of nuclear radiation on the thyroid gland in Japanese survivors. 
In 1970, Man retired from Brown University. Throughout her career, Man published 156 scientific papers and published her last paper in 1991. 
For her work, Man was awarded the American Thyroid Association's Distinguished Service Award in 1976 and the United Cerebral Palsy Award for Research.