Many families first notice permanent neonatal diabetes mellitus in the first weeks of life when a newborn has trouble gaining weight, seems unusually thirsty, pees often, or shows signs of dehydration like dry mouth and fewer wet diapers. Doctors are often alerted by very high blood sugar on a heel-prick test or blood draw, sometimes after the baby develops vomiting, fast breathing, or sleepiness that can signal diabetic ketoacidosis. In some cases, clues appear even earlier on prenatal ultrasound, such as poor growth in the womb, leading clinicians and parents to consider the first signs of permanent neonatal diabetes mellitus soon after birth.