New Zealand cricketer Jesse Ryder has tested positive for a performance-enhancing supplement and expects to be banned for about six months, according to a report.

The former international was only told he had tested positive after he was released from hospital following an assault in Christchurch earlier this year, RadioLive reports.

His lawyers say it was a poorly labelled weight-loss supplement and he didn't know he was taking a banned substance.

A Drug Free Sport NZ hearing was held earlier this month and a decision on a ban period - expected to be about six months - is expected to be announced this week.

Ryder has recently chosen to leave Wellington and play his cricket in Otago.