I left my milk kefir grains in the refrigerator for a few months. Are they still good?

Probably not. Kefir grains eat the milk sugars (lactose) out of the milk to live and to make their bacteria. This is why the milk gets more sour. When the grains run out of food, they begin to die. They’re living organisms and need food. Treat them like a pet and make sure you feed them. The only way to tell is to try and make a jar of kefir. If the milk turns sour and tart tasting then the good bacteria is working and your grains should be fine.