A diabetic emergency is any situation where blood sugar swings so far out of range that the body starts to shut down, creating an immediate risk of seizure, organ damage, coma, or death. There are three main types: severely low blood sugar (hypoglycemia), dangerously high blood sugar with acid buildup (diabetic ketoacidosis), and extremely high blood sugar with severe dehydration (hyperosmolar hyperglycemic state). Each one looks different, progresses differently, and requires a different response.
Severe Hypoglycemia: When Blood Sugar Drops Too Low
The American Diabetes Association classifies hypoglycemia in three levels. Level 1 is a blood glucose between 54 and 69 mg/dL, which most people can manage on their own. Level 2 is below 54 mg/dL, where cognitive function starts to decline noticeably. Level 3 is the true emergency: the person’s mental or physical state is so impaired that they need someone else’s help, regardless of the exact number on the meter.
The warning signs of low blood sugar tend to come on fast, sometimes within minutes. The person may become shaky, sweaty, flushed, and clammy. Their heart rate speeds up. They can appear confused, dizzy, irritable, or even aggressive, sometimes looking as though they’re intoxicated. If blood sugar continues to fall, seizures and loss of consciousness can follow.
Hypoglycemia most commonly happens in people taking insulin or certain oral diabetes medications. Skipping a meal, exercising more than usual, or taking too much medication can all trigger it. Because the brain depends almost entirely on glucose for fuel, a severe drop starves brain cells of energy and can cause lasting damage if not corrected quickly.
How to Respond to Low Blood Sugar
If the person is conscious and able to swallow, the standard approach is the 15-15 rule: give them 15 grams of fast-acting carbohydrate (about four glucose tablets, half a cup of juice, or a tablespoon of sugar) and wait 15 minutes. If they don’t feel better, repeat the dose. Once blood sugar comes back up, they should eat a small meal or snack with protein to keep it stable.
If the person is unconscious, seizing, or unable to swallow safely, do not put food or liquid in their mouth. This is when emergency glucagon becomes critical. Glucagon is a hormone that signals the liver to release stored sugar into the bloodstream. It’s available as a nasal spray that a bystander can administer by inserting the device into one nostril and pressing a plunger. No injection is needed. Injectable versions also exist. Anyone who lives with or regularly cares for a person on insulin should know where the glucagon is stored and how to use it before an emergency happens.
Call 911 if the person is unconscious, having a seizure, not responding to glucagon within about 10 minutes, or if you don’t have glucagon available.
Diabetic Ketoacidosis: Acid Buildup From Insulin Shortage
Diabetic ketoacidosis, or DKA, develops when the body doesn’t have enough insulin to move blood sugar into cells for energy. Without that insulin, the liver starts breaking down fat as an alternative fuel source. That process produces acids called ketones. When ketones build up faster than the body can clear them, the blood becomes dangerously acidic.
DKA is most associated with type 1 diabetes but can occur in type 2 as well, particularly during illness, infection, or if insulin doses are missed. It typically develops over hours to a day or two, not instantly. Early signs include extreme thirst, frequent urination, nausea, and fatigue. As it progresses, the person may develop a distinctive sweet or fruity smell on their breath (from the ketones), start breathing rapidly and deeply as the body tries to blow off excess acid, and become increasingly confused. Vomiting and abdominal pain are common.
Urine ketone test strips, available at most pharmacies, can help catch DKA before it becomes a full emergency. Results showing “large” amounts of ketones alongside high blood sugar and symptoms like nausea or rapid breathing signal the need for immediate medical attention. Left untreated, DKA can lead to coma and death. It is always a hospital emergency requiring IV fluids, insulin, and close monitoring.
Hyperosmolar Hyperglycemic State: Extreme Dehydration
Hyperosmolar hyperglycemic state, or HHS, is less well known than DKA but carries a higher mortality rate. It occurs almost exclusively in people with type 2 diabetes, often older adults. Blood sugar climbs above 600 mg/dL, sometimes reaching 1,000 or more, and the blood becomes severely concentrated as the body loses massive amounts of fluid through urination.
The key difference from DKA is that in HHS, the body still produces enough insulin to prevent significant ketone buildup, so the blood doesn’t turn acidic in the same way. Instead, the primary danger is profound dehydration and the thickening of the blood itself. This puts enormous strain on the heart, kidneys, and brain.
HHS develops more slowly than DKA, often over days or even a week or two. The person may initially just seem tired and thirsty. Because it creeps up gradually, especially in elderly people who may not recognize their thirst or have difficulty accessing fluids, it’s often caught late. By the time someone reaches the emergency room, they may be deeply confused, drowsy, or unresponsive. Like DKA, HHS is a hospital emergency that requires aggressive IV fluid replacement.
Telling the Emergencies Apart
From the outside, a diabetic emergency can be confusing because some symptoms overlap. A few physical clues help distinguish what’s happening:
- Skin: Low blood sugar typically makes the skin sweaty, flushed, and clammy. High blood sugar emergencies tend to cause dry skin and dry mouth from dehydration.
- Breath: A sweet, fruity smell on the breath points toward DKA and high blood sugar. Low blood sugar doesn’t produce this odor.
- Speed of onset: Hypoglycemia hits fast, within minutes to an hour. DKA builds over hours to days. HHS unfolds over days to weeks.
- Behavior: Hypoglycemia often makes a person jittery, sweaty, and agitated. DKA and HHS more commonly produce sluggishness, deep fatigue, and progressive confusion.
If you’re not sure whether someone’s blood sugar is high or low and they’re conscious and able to swallow, giving them a small amount of sugar is generally the safer bet. If their problem is low blood sugar, it will help immediately. If their problem is high blood sugar, the small amount won’t significantly worsen the situation in the short term, and you can call for help.
When to Call 911
The American Red Cross lists several signs that require immediate emergency medical treatment in a person with diabetes: trouble breathing, rapid or unusually deep breathing, seizures, confusion, and unresponsiveness. Other red flags include a fast heartbeat combined with cool and clammy skin, inability to walk steadily, or the person appearing intoxicated without having consumed alcohol.
If you encounter someone experiencing these symptoms and know they have diabetes, tell the 911 dispatcher. If the person is unconscious, place them on their side to protect their airway. Don’t try to give them food, drink, or insulin. If they have an emergency glucagon device and you suspect low blood sugar, use it while waiting for paramedics.
Speed matters in every type of diabetic emergency. Hypoglycemia can cause brain damage within minutes if blood sugar isn’t restored. DKA becomes progressively harder to reverse the longer ketone levels remain elevated. HHS carries a mortality rate significantly higher than DKA, largely because it’s recognized too late. In all three cases, the earlier the response, the better the outcome.