The motorway was closed in Staffordshire between Junctions 14 and 15 after the collision, in which the lorry jackknifed and blocked the carriageway, shortly after 12pm on Monday.
West Midlands Ambulance Service said two people had been taken to hospital.
A spokesman said: "Crews arrived to find a HGV and two cars that had been in collision.
"There were two occupants in one of the cars, a man and a woman, who both had to be cut free from their vehicle due to damage caused in this incident. They were both treated for injuries not believed to be serious before being taken to Royal Stoke University Hospital.
"The driver of the second car, a man, got himself out of his vehicle and was assessed and discharged at the scene.
"The HGV driver was uninjured in the collision."
The crash has led to traffic being taken off the M6 at Junction 14 and diverted along the A34 northbound to the A500 at Hanford. From there vehicles travelled west until they rejoined the motorway at Junction 15.
A lorry has jackknifed near Stafford services M6 Northbound, we are diverting traffic from the M6 onto the A34, working with our partners @NationalHways to get you moving ASAP, please bear with us as we do this with your safety being our primary concern 4914 pic.twitter.com/zQSFOmDKuQ— CMPG (@CMPG) September 27, 2021
As of 4.15pm queues were stretching back to Junction 12.