The race day medication rules have been expanded to include blood tests and vitamins.

It means horses cannot be injected within one clear day of racing.

The rule makes it an offence for any trainer, anyone in charge of a horse, or vet, to insert a needle into a horse later than midnight on Thursday if the horse is racing on Saturday.

Racing Australia says there is no scientific evidence to support a health and welfare imperative to treat horses by hypodermic injection within one clear day of racing.

RA said blood tests taken late on the Thursday before racing on the Saturday should give the same, or close to the same, result.

Trainers can ask stewards for an exception to the ban if there are clinical issues.

The rule comes into effect on October 1.