When your blood sugar drops below 70 mg/dL, your body enters a state called hypoglycemia. What happens next depends on how far it falls and how quickly you respond. At mildly low levels, you’ll feel shaky and hungry. Below 54 mg/dL, your brain starts losing its primary fuel source, and confusion, seizures, and loss of consciousness become real possibilities.
How Your Body Fights Back
Your brain runs almost entirely on glucose, so your body treats a blood sugar drop like an emergency. As levels start to fall, a cascade of hormones kicks in: glucagon tells your liver to release stored sugar, adrenaline speeds up the process, and cortisol and growth hormone work to keep glucose available longer. At the same time, your pancreas dials back insulin production to stop pulling more sugar out of your bloodstream.
This counterattack is why you feel the way you do when your blood sugar dips. The adrenaline surge produces that shaky, sweaty, heart-pounding feeling. It’s unpleasant, but it’s actually useful. Those sensations are your body’s built-in alarm system, warning you to eat something before things get worse.
What Low Blood Sugar Feels Like
Mild hypoglycemia, around 54 to 70 mg/dL, produces symptoms most people recognize: shakiness, sweating, sudden hunger, a racing heartbeat, and irritability. You can usually treat it yourself and feel better within minutes.
When blood sugar drops below 54 mg/dL, the symptoms shift. Your brain isn’t getting enough fuel, so the signs become neurological: confusion, difficulty walking, blurred vision, slurred speech, and behavior that looks strange to people around you. You may not realize anything is wrong, which is part of what makes this level dangerous. Below roughly 36 mg/dL, seizures become a serious risk. One case report described an 11-year-old with type 1 diabetes who developed drug-resistant epilepsy after a single episode at 35 mg/dL.
At the most severe level, you can lose consciousness entirely. This is classified as Level 3 hypoglycemia, defined not by a specific number on a glucose meter but by the fact that you need someone else to help you recover.
Brain Damage and Long-Term Risks
Your brain is uniquely vulnerable during severe hypoglycemia. Prolonged glucose deprivation can kill neurons, shrink gray matter, and cause lasting cortical damage. The mechanisms involved include the same kinds of inflammatory and protein-buildup processes seen in dementia, which is why repeated severe episodes are linked to cognitive decline over time.
A single brief episode of mild low blood sugar won’t cause permanent harm. The concern is with blood sugar that drops very low, stays low for an extended period, or happens over and over again. Newborns are especially vulnerable. Neonatal hypoglycemia has been associated with structural brain damage and the later development of epilepsy.
Heart Rhythm Problems
Low blood sugar doesn’t only affect the brain. It also stresses the heart. Hypoglycemia triggers adrenaline release, which can disrupt the electrical signals that keep your heart beating in a regular rhythm. In some people, this leads to a prolonged QT interval, a change in the heart’s electrical cycle that increases the risk of dangerous arrhythmias. People with certain genetic variations affecting potassium channels in heart and pancreatic cells are particularly susceptible, but even without a genetic predisposition, severe lows can put strain on the cardiovascular system.
Why Some People Stop Feeling the Warning Signs
One of the most dangerous complications of frequent low blood sugar is losing the ability to feel it coming. This is called hypoglycemia unawareness, and it affects about 25% of people with type 1 diabetes and an estimated 10 to 15% of people with type 2 diabetes who use insulin or certain oral medications. Continuous glucose monitors are revealing that the true percentage may be even higher.
The mechanism is straightforward but insidious. Each time your blood sugar drops low, the threshold at which your body sounds the alarm shifts downward. If you had symptoms at 60 mg/dL yesterday, today you might not feel anything until you’re at 55. Over time, your first warning sign may be confusion or near-unconsciousness, with none of the earlier shakiness or sweating that would have prompted you to eat. Carefully avoiding all lows for a period of several weeks can help reset this threshold, gradually restoring the body’s early warning system.
Drops That Happen During Sleep
Nearly half of all hypoglycemic episodes, and more than half of all severe ones, occur at night during sleep. This makes nocturnal hypoglycemia a particular concern for people on insulin. You can’t feel symptoms as easily while asleep, and you can’t reach for a snack if you’re unconscious.
Signs that a nighttime low may have occurred include waking up drenched in sweat, restless or irritable sleep, nightmares, changes in breathing patterns, and trembling or shaking. A bed partner may notice these signs before you do. Waking up with a headache or feeling unusually exhausted can also point to an overnight drop. Continuous glucose monitors with low-glucose alarms have made a significant difference for people prone to these episodes.
How to Treat a Low in the Moment
The standard approach is called the 15-15 rule: eat 15 grams of fast-acting carbohydrates, wait 15 minutes, then check your blood sugar again. If it’s still below 70 mg/dL, repeat the process. Good sources of 15 grams of fast-acting carbs include four glucose tablets, four ounces of juice or regular soda, or a tablespoon of honey. The key word is “fast-acting.” A chocolate bar or a handful of nuts contains fat that slows digestion and delays the sugar from reaching your bloodstream.
Once your blood sugar stabilizes, eat a small meal or snack with protein and complex carbohydrates to keep it from dropping again.
When Someone Can’t Treat Themselves
If a person is too confused, seizing, or unconscious to swallow safely, do not try to put food or liquid in their mouth. This is where emergency glucagon comes in. Glucagon is a hormone that signals the liver to dump its stored sugar into the bloodstream, and it’s available in several forms that don’t require medical training to use.
A nasal spray version delivers a powdered dose into one nostril, no injection needed. An auto-injector pen works similarly to an epinephrine pen for allergies, delivering a shot under the skin of the arm, stomach, or thigh. Traditional glucagon kits require mixing a powder with liquid before injecting into muscle, which makes them slightly more complicated under pressure. All of these are prescription products, and anyone at risk for severe lows should have one accessible and make sure the people around them know where it is and how to use it.
After administering glucagon, turn the person on their side in case they vomit, and call emergency services if they don’t regain consciousness within 15 minutes.