A southern Tasmanian teenager has died after drinking a lethal brew made from poppy heads.

The 17-year-old was found dead at his home on Sunday evening.

Inspector John Arnold says the young man died after brewing a batch of stolen poppy heads into a tea.

"If you consume those opioids in that unregulated way, the consequences can be obviously lethal," he said.

Inspector Arnold says poppy-related deaths are unusual.

"A 50-year-old northern Tasmanian man died in similar circumstances in February last year," he said.

"Prior to that, the previous death associated with poppy ingestion was back in 2004."

With the poppy harvest approaching, Inspector Arnold warns it is a serious offence to steal and possess poppy heads.

The coroner will investigate the death.

Tasmania's lucrative poppy crop is worth about $100 million.