Drug testing organisations are warning about unusually high doses of MDMA

The Drug Foundation's Sarah Helm says the stimulant's normally at the lower end of harm, but it's unlawful and unregulated - so the exact contents can be a concern.

She says about half of pills being tested are more than twice the normal strength.

Helm says users need to be wary.

She says there's a risk of over-amping -- a type of overdose -- and people should ask for help at that point.