Last year, Tim Chevalier received the first of many coverage denials from his insurance company for the hair removal procedure he needed as part of a phalloplasty, the creation of a penis.

Electrolysis is a common procedure among transgender people like Chevalier, a software developer in Oakland, California. In some cases, it’s used to remove unwanted hair from the face or body. But it’s also required for a phalloplasty or a vaginoplasty, the creation of a vagina, because all hair must be removed from the tissue that will be relocated during surgery.

Chevalier’s insurer, Anthem Blue Cross, told him he needed what’s known as a prior authorization for the procedure. Even after Chevalier received the authorization, he said, his reimbursement claims kept getting denied. According to Chevalier, Anthem said the procedure was considered cosmetic.

Many trans patients have trouble getting their insurers to cover gender-affirming care. One reason is transphobia within the U.S. health care system, but another involves how medical diagnoses and procedures are coded for insurance companies. Nationwide, health care providers use a list of diagnostic codes provided by the International Classification of Diseases, Tenth Revision, or ICD-10. And many of those, advocates for transgender people say, haven’t caught up to the needs of patients. Such diagnostic codes provide the basis for determining which procedures, such as electrolysis or surgery, insurance will cover.