The Federal Motor Carrier Safety Administration's (FMCSA) requires commercial drivers who fall under the following categories to obtain medical cards for CDL:
When your vehicle has a gross weight of 10,001 or over.
The vehicle which you are driving can seat over 15 passengers.
When receiving immediate payment for transporting over 8 passengers.
If your vehicle has been placarded due to the hauling of hazardous materials.
The FMCSA has given those with diabetes, vision impairment, hearing disabilities or seizures an opportunity to apply for a CDL medical card exemption. You can find more information about exemptions here.
The CDL or DOT medical card is valid for two years. If the medical card expires, you will no longer be an eligible commercial truck driver until you get it renewed. So make sure to mark your calendar to remember to renew the DOT medical card.