If you take methadone will you be able to get high on herion?

Yes, methadone is an opiate blocker and will block the effects of heroine.

----------------------------------

Improvement

Methadone does not contain an opiate blocker at all. It has a cross-tolerance with opioids, and higher doses of methadone can reduce the high: but from first hand experience I can tell you categorically that methadone does not totally block the high you get from taking heroin.