Hyperglycemia Say: hi-per-gly-see-me-uh Glucose (a type of sugar) is the body's main energy source. Hormones, such as insulin, control the level of glucose in the blood. It's unhealthy if a person's glucose levels get too high or too low. Hyperglycemia occurs when the levels get too high. This can happen to someone who has diabetes but doesn't know it yet. It also can happen to someone whose diabetes is not under control. Signs of hyperglycemia include increased urination (peeing), extreme thirst, and unexplained weight loss. Back to Articles Related Articles Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.