Dangerous blood sugar levels depend on whether the level is too high (hyperglycemia) or too low (hypoglycemia):
- Low blood sugar (hypoglycemia) is considered dangerous when it falls below 70 mg/dL. Levels below 54 mg/dL call for immediate action, and levels under 40 mg/dL can be life-threatening. Symptoms may include weakness, shaking, sweating, headache, hunger, blurry vision, and in severe cases, loss of consciousness or seizures.
- High blood sugar (hyperglycemia) is considered dangerous when levels rise above 180 mg/dL within two hours of eating. A blood sugar reading of 300 mg/dL or higher is particularly concerning and warrants contacting a doctor, especially if there are two consecutive readings that high. Extremely high levels (600 mg/dL or higher) can cause life-threatening conditions such as hyperosmolar hyperglycemic syndrome (HHS) or diabetic ketoacidosis (DKA), which require immediate emergency treatment. Symptoms of dangerously high blood sugar include extreme thirst, frequent urination, dry skin, confusion, hallucinations, nausea, vomiting, and fruity-smelling breath.
If blood sugar is too high or too low, immediate medical attention may be necessary to prevent serious complications such as diabetic coma or permanent damage to organs and nerves. It is important that individuals with diabetes monitor their blood sugar regularly and consult with their doctor to understand their own target ranges and when to seek help based on their symptoms and readings. In summary:
- Dangerous low blood sugar: below 70 mg/dL, emergency below 54 mg/dL, life-threatening below 40 mg/dL
- Dangerous high blood sugar: above 180 mg/dL (post-meal), very dangerous at 300 mg/dL or higher, critical at 600 mg/dL or higher requiring emergency care
This guidance applies to people with and without diabetes, with specific target ranges advised by healthcare providers according to individual needs. If you or someone else has symptoms of extremely high or low blood sugar, seek medical help immediately.
