Yes, LIPID is a Scrabble word!

Letter values in Scrabble US: L 1, I 1, P 3, I 1, D 2.

Is it a valid word?

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

an oily organic compound insoluble in water but soluble in organic solvents; essential structural component of living cells (along with proteins and carbohydrates)