TUESDAY, Aug. 16, 2016 (HealthDay News) -- Female doctors in the United States make much less than their male colleagues, a new study finds.

Researchers examined more than 3 million Medicare reimbursement claims received by doctors in 13 medical specialties in 2012. Overall, female doctors got $34,126 less than male doctors, the investigators found.

After the researchers adjusted for working hours, productivity and years of experience, they found that female doctors were reimbursed $18,677 less than their male colleagues.

The study found that the largest gender gaps were in nephrology ($16,689) and rheumatology ($15,405). The narrowest gaps were in hematology ($10,115), critical care ($4,360) and medical oncology ($3,971).

The study was published online Aug. 15 in the Postgraduate Medical Journal.

Tejas Desai of the division of nephrology at WG (Bill) Hefner VA Medical Center in Salisbury, N.C., and colleagues said their study does not explain why female doctors get paid less than males. But, they noted in a journal news release, the findings show that "the commonly held theories of why monetary disparities exist need to be revisited."

More information

The Pew Research Center has more on the gender pay gap in the United States.