When your blood sugar drops below 70 mg/dL, you need to eat or drink 15 grams of fast-acting carbohydrates right away, then wait 15 minutes and recheck. This approach, called the 15-15 rule, is the standard first response for mild to moderate low blood sugar. Acting quickly matters because blood sugar can continue falling, and symptoms get worse the lower it goes.
How to Recognize Low Blood Sugar
Your body sends two waves of warning signals as blood sugar drops. The first wave is physical: sweating, shakiness, a racing heartbeat, sudden anxiety, and intense hunger. These are your body’s stress response kicking in, and they tend to show up early, when blood sugar is mildly low (between 54 and 70 mg/dL).
If blood sugar keeps falling below 54 mg/dL, a second wave of symptoms appears as your brain starts running short on fuel. These include weakness, dizziness, difficulty concentrating, confusion, blurred vision, and behavior changes that can look like intoxication. At the most severe level, a person may become combative, lose coordination, have seizures, or lose consciousness entirely.
Not everyone experiences symptoms in that tidy order. Some people, especially those who have frequent low blood sugar episodes, gradually lose the ability to feel early warning signs. Their body essentially recalibrates, triggering symptoms at lower and lower glucose levels while the threshold for passing out stays the same. This creates a dangerous gap where a person might feel fine one moment and lose consciousness the next. Continuous glucose monitors are particularly useful for people in this situation, since the device can sound an alarm before blood sugar reaches a critical low. The encouraging news: avoiding lows for a stretch of time can help reset the body’s alarm system so symptoms become noticeable again.
The 15-15 Rule, Step by Step
If your blood sugar is below 70 mg/dL, or you’re feeling symptoms and can’t test, follow this process:
- Eat or drink 15 grams of fast-acting carbohydrates. Good options include half a cup (4 ounces) of fruit juice or regular soda, 3 glucose tablets, 1 tablespoon of sugar or honey, 6 to 7 hard candies, or one tube of glucose gel.
- Wait 15 minutes. Give your body time to absorb the sugar. Resist the urge to eat more immediately, because overcorrecting can send blood sugar too high.
- Recheck your blood sugar. If it’s still below 70 mg/dL, repeat with another 15 grams of carbohydrates. Continue this cycle until your reading is back in range.
- Eat a balanced snack or meal. Once your blood sugar is above 70 mg/dL, follow up with something that includes protein, fat, and complex carbohydrates. A handful of crackers with peanut butter or a small meal works well. This prevents a second drop after the fast-acting sugar wears off.
Stick with simple, fast-digesting sugar for the initial treatment. Chocolate bars, cookies, or fatty foods digest slowly and won’t raise your blood sugar fast enough when it counts.
What to Do in a Severe Episode
If someone is confused, unable to swallow safely, having seizures, or unconscious, do not try to put food or liquid in their mouth. They could choke. This is a medical emergency.
Glucagon is the rescue treatment for severe low blood sugar. It’s a hormone that signals the liver to release stored glucose into the bloodstream. Glucagon comes in several forms: injectable kits that require mixing a powder with liquid, prefilled auto-injectors that work like an EpiPen, and nasal spray versions that don’t require an injection at all. The shot can be given in the thigh, upper arm, or stomach. Nasal spray is simply sprayed into one nostril while the person is lying on their side.
If you take insulin or medications that can cause low blood sugar, keep glucagon accessible and make sure the people around you, whether that’s a partner, coworker, or roommate, know where it is and how to use it before an emergency happens. After giving glucagon, call emergency services. The person should typically regain consciousness within 15 minutes, but they will need medical follow-up.
Common Causes of Low Blood Sugar
For people with diabetes, the most frequent triggers are taking too much insulin, not eating enough carbohydrates relative to your insulin dose, and mistiming meals or medication. Physical activity is another major factor because exercise makes your muscles pull glucose from the bloodstream more efficiently, which can cause a drop during or hours after a workout. Alcohol adds another layer of risk because it blocks the liver’s ability to release stored glucose, leaving your body without its backup supply.
Nighttime lows deserve special attention. They can happen after a particularly active day, after exercising close to bedtime, after drinking alcohol in the evening, or from taking too much insulin before sleep. You may sleep through mild symptoms entirely, waking up with a headache, feeling groggy, or finding damp sheets from sweating overnight. A continuous glucose monitor with low alerts can catch these episodes while you sleep.
Low Blood Sugar Without Diabetes
You don’t need to have diabetes to experience low blood sugar. Reactive hypoglycemia causes blood sugar to drop within four hours after eating, and in many cases the exact reason isn’t clear. It tends to be linked to what and when you eat, particularly meals high in refined carbohydrates that cause a rapid spike followed by an overcorrection from your body’s insulin response.
Other possible causes include alcohol consumption, prior stomach or bariatric surgery (which changes how quickly food moves through your digestive system), certain inherited metabolic conditions, and rarely, tumors that produce excess insulin. If you’re experiencing repeated episodes of low blood sugar and you don’t take diabetes medication, that pattern is worth investigating with a doctor, because identifying the underlying cause changes how you manage it.
Preventing Future Episodes
Most lows are preventable with a few adjustments. If you use insulin, check your blood sugar before meals, before driving, before exercise, and before bed. Keep fast-acting carbohydrates within reach at all times: in your bag, your car, your desk, and on your nightstand. Glucose tablets are compact and won’t melt or spill, making them a reliable option to stash everywhere.
Pay attention to patterns. If you notice lows after certain activities or at certain times of day, that information helps you or your healthcare team adjust insulin doses or meal timing. Eating consistent meals with a mix of carbohydrates, protein, and fat slows glucose absorption and helps prevent both spikes and crashes. Before and during exercise, check your levels more frequently and have a carbohydrate-rich snack ready if you’re trending downward.
For people with reactive hypoglycemia, eating smaller, more frequent meals and choosing complex carbohydrates over refined ones (whole grains instead of white bread, fruit instead of candy) can smooth out the blood sugar swings that trigger episodes. Pairing carbohydrates with protein or healthy fat at every meal slows digestion and reduces the sharp insulin response that leads to a post-meal crash.