It's hard to say for sure. If you are sure the new growth is from the root and not from just above the root, you are probably getting growth from the rootstock. In "citrus country" this would almost always be a citrus variety with limited culinary value. But some Meyer lemons grown for indoor use may be grown on their own roots. Some clues would be leaf shape, branching habit and thorniness of the new growth.

If your Meyer lemon was a dwarf it was grafted onto another, hardier citrus, most likely sour orange. It is unlikely to be a fruit you want.

Rosefolly