[ A brief thought of 'ew, weres' flicks across Strange's mind before he realizes stop that, you didn't even know any werebeasts before Portland, don't be species-racist ]

I suggest trying eat or drink as a bat before trying to tweak the spell itself. I don't know which would be worse, eating as a bat or not eating as a gem, but not eating as a bat would undoubtedly be the worst choice of the three.