Yes, HOMEOPATHY is a Scrabble word!

Letter values in Scrabble US: H 4, O 1, M 3, E 1, O 1, P 3, A 1, T 1, H 4, Y 4.

Is it a valid word?

HOMEOPATHY is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a method of treating disease with small amounts of remedies that, in large amounts in healthy people, produce symptoms similar to those being treated

Not playable in Scrabble US: HOMOEOPATHY.