When your blood sugar drops below about 70 mg/dL, your body triggers a cascade of warning signs designed to get you to eat something fast. You might feel shaky, sweaty, and suddenly anxious. If levels keep falling, the symptoms shift from uncomfortable to dangerous, affecting your brain, your heart, and eventually your consciousness.
Early Warning Signs
Your body’s first response to falling blood sugar is to flood your system with stress hormones, primarily adrenaline. This is the same fight-or-flight response you’d feel during a scare, and it produces a recognizable set of symptoms: sweating, a pounding or racing heart, trembling hands, sudden anxiety, and intense hunger. These signs typically appear when blood sugar dips to around 70 mg/dL or slightly below, and they serve as an early alarm system.
Most people notice these symptoms clearly enough to act on them. They feel “off” in a way that’s hard to ignore. The hunger in particular can be fierce and urgent, distinct from ordinary appetite.
What Happens as Sugar Drops Further
If blood sugar continues falling below roughly 54 mg/dL, the symptoms change character. Your brain, which depends almost entirely on glucose for fuel, starts to malfunction. This produces a different category of symptoms: confusion, difficulty concentrating, irritability, slurred speech, blurred vision, and poor coordination. Some people become combative or act as though they’re intoxicated.
At very low levels, hallucinations, seizures, loss of consciousness, and coma can occur. Prolonged severe episodes can cause brain injury and, in rare cases, death. The shift from the early adrenaline-driven symptoms to these brain-related symptoms is significant because once confusion sets in, you may not be able to treat yourself.
How Your Body Tries to Correct It
Your body doesn’t just sit passively while glucose drops. It deploys a backup system centered on two hormones: glucagon and adrenaline. Glucagon, released by the pancreas, signals your liver to dump stored glucose into the bloodstream. Adrenaline does something similar while also producing those noticeable warning symptoms. Research published in the American Journal of Physiology shows these two hormones form a redundant safety net. If one fails, the other can compensate. But when both are impaired, which happens in some people with long-standing diabetes, the body loses its ability to self-correct.
This redundancy is why most healthy people rarely experience dangerous lows. Their hormonal safety net catches the drop before it becomes serious.
Common Causes
The most frequent cause of low blood sugar is diabetes medication, particularly insulin and a class of drugs called sulfonylureas. These medications actively lower blood glucose, and if the dose is too high, a meal is skipped, or exercise burns through glucose faster than expected, levels can plummet.
Several everyday factors raise the risk of an episode: missing or delaying meals, exercising more than usual, drinking excessive alcohol, and even hot weather. Certain antibiotics and other medications can also amplify the blood-sugar-lowering effects of diabetes drugs, sometimes severely enough to require hospitalization.
People without diabetes can experience low blood sugar too, though it’s less common. This can happen after eating a large carbohydrate-heavy meal (called reactive hypoglycemia), when the body overshoots its insulin response and drives glucose too low a few hours later. Other causes include prolonged fasting, heavy alcohol use, certain tumors, and hormonal deficiencies.
Low Blood Sugar While You Sleep
Nighttime episodes are particularly concerning because you’re not awake to notice the early warning signs. According to Johns Hopkins Medicine, symptoms of nocturnal hypoglycemia include restless or irritable sleep, night sweats, clammy skin, trembling, changes in breathing patterns, nightmares, and a racing heartbeat. You might wake up with a headache, feel unusually tired, or find damp sheets without knowing why.
A bed partner often notices these signs before the person experiencing them does. If morning headaches and drenched pajamas become a pattern, nighttime blood sugar dips are worth investigating.
Hypoglycemia Unawareness
One of the more dangerous complications of repeated low blood sugar is that your body can stop sending warning signals. This condition, called hypoglycemia unawareness, occurs when frequent episodes dull the hormonal alarm response. Instead of feeling shaky and sweaty at 70 mg/dL, you feel nothing until your brain is already starving for glucose and you’re too confused to help yourself.
This is most common in people with type 1 diabetes who have had the disease for many years. Research shows that those with unawareness spend significantly more time with dangerously low blood sugar and have longer-lasting episodes compared to people who still feel their warning signs. The cycle is self-reinforcing: more lows lead to less awareness, which leads to more severe lows.
Long-Term Risks of Repeated Episodes
A single mild episode, caught and treated quickly, is unlikely to cause lasting harm. But severe or frequent low blood sugar carries real consequences over time. Prolonged episodes can injure brain cells, cause abnormal heart rhythms, and increase clotting risk. Studies show a mortality risk of 2% to 4% after a severe episode in people with diabetes.
The cardiovascular effects are particularly notable. Low blood sugar triggers a surge of stress hormones that increase inflammation, promote blood clotting, impair blood vessel function, and disrupt the heart’s electrical system. Large clinical trials have identified severe hypoglycemia as one of the strongest predictors of heart attacks, strokes, and death in people with type 2 diabetes, with the risk of death roughly two to four times higher in those experiencing repeated severe episodes.
How to Treat a Low Blood Sugar Episode
The standard approach is called the 15-15 rule. If your blood sugar is at or below 70 mg/dL, eat or drink 15 grams of fast-acting carbohydrates. Good options include four glucose tablets, four ounces of juice, or a tablespoon of sugar or honey. Wait 15 minutes, recheck your blood sugar, and repeat if it’s still below 70.
If your blood sugar is at or below 54 mg/dL, double the dose to 30 grams of fast-acting carbs before waiting and rechecking. This more aggressive approach matches the greater urgency of a deeper drop.
For someone who is unconscious or unable to swallow, emergency glucagon is the treatment. This comes in several forms: a nasal spray powder that a bystander sprays into one nostril (no breathing required, it absorbs through the nasal lining), a pre-filled auto-injector pen given under the skin, and a traditional injection kit that requires mixing before use. Anyone living with a person who takes insulin should know where the glucagon is stored and how to use it.
Once blood sugar stabilizes after a moderate or severe episode, eating a more substantial snack or meal with protein and complex carbohydrates helps prevent another dip. The fast-acting sugar buys time, but it burns off quickly without something more sustaining behind it.