Yes, FIBRIN is a Scrabble word!

Letter values in Scrabble US: F 4, I 1, B 3, R 1, I 1, N 1.

Is it a valid word?

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

a white insoluble fibrous protein formed by the action of thrombin on fibrinogen when blood clots; it forms a network that traps red cells and platelets