My Husband Is 88 Is On Keppra 750mg Bid And

My husband is 88 is on Keppra 750mg bid and has been for the last two years. He also has late stages of Alzheimer's . His Keppra level is 23.0, we cannot get a proper range measurement from the lab. Is this level within the proper range or should it be modified. Lately we have observed what we think are breakthroughs.