The UFC middleweight contender was handed a six-month suspension by USADA on Monday, the UFC's anti-doping partner announced on its website.
The news of a shorter suspension than otherwise thought was first reported by MMA Fighting's Ariel Helwani on Monday morning.
In December, Romero tested positive for a substance called Ibutamoren, a growth hormone secretagogue. The National Center for Biotechnology Information describes the substance, which is prohibited under the UFC's anti-doping policy, as stimulating growth hormone release "through a pituitary and hypothalamic receptor."
Romero, 38, denied knowingly taking the substance and has claimed all along that it came from a contaminated substance.