When your blood sugar drops below about 70 mg/dL, your body launches a stress response that produces a cascade of increasingly serious symptoms. At first you might feel shaky, sweaty, and intensely hungry. If levels keep falling, the effects shift from uncomfortable to dangerous, potentially causing seizures, loss of consciousness, and in rare cases, lasting brain damage or death.
Your Body’s Emergency Response
Your brain runs almost entirely on glucose, so when blood sugar starts dropping, your body treats it as an emergency. The first defense is hormonal: your pancreas releases glucagon, a hormone that signals your liver to dump stored sugar into the bloodstream. At the same time, your adrenal glands release adrenaline, which does several things at once. It tells the liver to produce even more glucose, slows insulin release, and reduces how much glucose your muscles absorb, all to redirect sugar toward your brain.
If the drop continues, slower-acting stress hormones like cortisol kick in. Cortisol shifts your body’s fuel use away from glucose, pushing muscles and other tissues to burn fat instead, preserving whatever glucose remains for your brain. This layered response is why low blood sugar feels so physical. The shakiness, racing heart, and sweating aren’t the hypoglycemia itself. They’re side effects of adrenaline flooding your system.
Early Warning Signs
The first symptoms are driven by that adrenaline surge and tend to come on quickly:
- Shakiness or trembling
- Sweating, sometimes with pale skin
- A fast or irregular heartbeat
- Sudden intense hunger
- Anxiety, irritability, or nervousness
- Dizziness or lightheadedness
- Tingling or numbness in your lips, tongue, or cheek
These symptoms are your body’s alarm system, and they serve a purpose. They’re noticeable enough to prompt you to eat something. Most people who catch a low at this stage can correct it within minutes with a small amount of fast-acting sugar.
What Happens as Blood Sugar Keeps Dropping
If blood sugar isn’t corrected, the symptoms shift from adrenaline-driven warnings to signs that your brain is running short on fuel. You may have difficulty concentrating, slurred speech, blurred vision, or confusion. Coordination suffers, and your behavior can change in ways that look like intoxication, which sometimes delays help from bystanders.
At this stage, thinking clearly enough to help yourself becomes harder. Some people become combative or uncooperative without realizing it. Others feel extreme fatigue or weakness that makes it difficult to walk to a kitchen or open a juice box. This is the window where the situation can become genuinely dangerous, because the lower blood sugar falls, the less capable you are of fixing it on your own.
Severe Hypoglycemia
Severe hypoglycemia means blood sugar has dropped low enough that you need someone else’s help. It’s defined by altered mental state, extreme weakness, seizures, fainting, or coma. Untreated severe episodes can cause brain or organ damage, and they carry roughly three times the risk of death compared to people who don’t experience them.
The heart is also vulnerable during severe lows. Hypoglycemia increases platelet activity and changes blood flow patterns in ways that can trigger cardiac events or strokes, particularly in people who already have cardiovascular disease. For someone with existing heart problems, a severe low isn’t just a sugar problem. It’s a cardiovascular event in its own right.
When It Happens During Sleep
Low blood sugar that occurs overnight, called nocturnal hypoglycemia, is particularly risky because you can’t recognize or respond to symptoms while asleep. Blood sugar below 70 mg/dL during sleep may cause restless or irritable sleep, night sweats, clammy skin, trembling, nightmares, changes in breathing patterns, or a racing heartbeat. A bed partner may notice these signs before the person themselves.
People who experience nighttime lows often wake up with a headache, feeling exhausted, or with damp sheets, without knowing what happened. Continuous glucose monitors with low-threshold alarms are one of the most effective tools for catching these episodes, since they can wake you before levels reach a dangerous point.
Losing the Ability to Feel Warnings
One of the more dangerous complications of repeated low blood sugar is that your body can stop sounding the alarm. When someone experiences frequent hypoglycemic episodes, their hormonal response to low blood sugar becomes blunted over time. The adrenaline surge that normally produces shaking, sweating, and a racing heart gets dialed down, so the person feels fine until their brain is already starved of glucose. They skip the warning stage entirely and go straight to confusion, seizures, or unconsciousness.
This creates a vicious cycle: each unrecognized episode makes the next one harder to detect and more likely to become severe. The condition is most common in people with type 1 diabetes or those with type 2 diabetes who use insulin, particularly if they’ve been managing their blood sugar aggressively.
How to Treat a Low in the Moment
The standard approach is the 15-15 rule: eat 15 grams of fast-acting carbohydrate, wait 15 minutes, then check your blood sugar again. If it’s still low, repeat. Fifteen grams of carbohydrate looks like any one of these:
- 3 glucose tablets
- Half a cup (4 ounces) of fruit juice or regular soda
- 6 or 7 hard candies
- 1 tablespoon of sugar
The key is speed. You want sugar that hits the bloodstream fast, not complex carbs or foods with fat and protein that slow digestion. A candy bar or a peanut butter sandwich won’t work nearly as quickly as juice or glucose tablets.
When Someone Can’t Treat Themselves
If a person is too confused to eat, unable to swallow safely, losing consciousness, or having a seizure, they need glucagon. This is a hormone that tells the liver to release its sugar stores into the bloodstream, and it works even when someone can’t eat or drink. Emergency glucagon comes in several forms: a nasal spray powder that gets sprayed into one nostril (no inhaling required), a pre-filled auto-injector that goes under the skin, and a traditional injection kit that requires mixing before use.
Anyone who lives with or regularly spends time with a person at risk for severe lows should know where the glucagon is stored and how to use it. Keeping a kit in a bedside drawer, a purse, or a gym bag makes it accessible when seconds matter. If glucagon isn’t available or the person doesn’t respond within about 15 minutes, call emergency services.