The short answer to the question “Are occasional drivers required to drug test?” is yes.

Any driver who operates a commercial motor vehicle, as defined in 49 CFR §382.107, must hold a commercial driver’s license (CDL). These drivers must comply with the drug and alcohol testing requirements under 49 CFR Parts 40 and 382. (See 49 CFR §383.3 for reference.)

This rule applies to all types of drivers. It includes full-time drivers, regularly-employed drivers, casual drivers, intermittent or occasional drivers, leased drivers, and independent owner-operator contractors.

See federal register notice for more on leased drivers.

https://www.fmcsa.dot.gov/regulations/drug-alcohol-testing/occasional-drivers-my-company-purchased-large-truck-over-26001-lbs

See this:

Occasional Drivers: Suppose your company bought a large truck with a gross vehicle weight rating (GVWR) over 26,001 lbs. You do not currently employ any CDL drivers. A family friend, who is not an employee, drives the truck occasionally as a favor without receiving any compensation.

Do you still need a DOT drug and alcohol testing program?

Yes.

According to §382.103, your company must implement a DOT drug and alcohol program for all drivers who operate a commercial motor vehicle (CMV) that requires a CDL.

Section §382.107 defines a “Driver” as any person who operates a commercial motor vehicle. This includes full-time, regularly-employed, casual, intermittent, or occasional drivers. It also includes leased drivers and independent owner-operator contractors.