There are 19 13-letter words that start with 'bio'.
Note: These 19 13-letter words that start with 'bio' are found from the USA & Canada version of the tournament Scrabble word list.
Also see words start with biom, bios, biog, biot, bioc, biop, biol, bioe, bior, biof, bion, bioa, biod, bioh, biow, biov.
4-letter words start with 'bio' (2)