If the medical examiner’s certificate has expired, you must obtain a new one and provide it to your State Driver Licensing Agency (SDLA). If you require a variance and it has expired, you must renew it with FMCSA. Your State may require retesting and additional fees to get back your CDL privileges. If allowed by your SDLA, you may also change your self-certification to an operating category that does not require a medical certificate.
More information can be found on the FMCSA medical program web site.