How to tell freeradius of the encryption used in DB

Hi, I am testing freeradius. I use dialup admin and mysql to add users, which is configured to store passwords in md5. The attribute is User-Password. Used radtest for testing, but seems radtest is only able to recognize cleartext password. How to tell freeradius that passwords are in md5? Should i need to use other client aside from radtest? Thanks so much, Det