When your blood sugar drops below 70 mg/dL, the fastest way to bring it back up is to eat 15 grams of fast-acting carbohydrates, wait 15 minutes, and recheck. This approach, known as the 15-15 rule, is the standard method recommended by the CDC for treating mild to moderate low blood sugar. But regulation goes beyond the immediate fix. Preventing repeated drops requires understanding why they happen and building habits that keep your levels stable throughout the day.
The 15-15 Rule for Immediate Treatment
When you feel symptoms of low blood sugar (shakiness, sweating, confusion, irritability, or sudden hunger), eat 15 grams of quick-acting carbohydrates. Wait 15 minutes, then check your blood sugar again. If it’s still below 70 mg/dL, repeat the process. Keep going until your reading is back in your target range.
What counts as 15 grams of fast-acting carbohydrates? Any of these will work:
- 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 word is “fast-acting.” You want simple sugars that hit your bloodstream quickly. A candy bar or cookie contains fat, which slows digestion and delays the sugar reaching your blood. Stick with the options above when you need a quick correction. Once your blood sugar stabilizes, eat a small meal or snack with protein and complex carbohydrates to keep it from dropping again.
For young children, especially infants and toddlers, 15 grams may be too much. A pediatrician can recommend the right amount based on the child’s size.
Why Blood Sugar Drops in the First Place
If you take insulin or certain diabetes medications, the most common trigger for low blood sugar is a mismatch between your medication dose and your food intake or activity level. Skipping a meal, eating less than usual, or exercising more intensely than expected can all tip the balance.
People without diabetes can also experience low blood sugar. Reactive hypoglycemia causes a drop within four hours after eating, often following a meal high in refined carbohydrates. Your body overproduces insulin in response to the sugar spike, then overshoots on the way down. The exact cause isn’t always clear, but it tends to be connected to what and when you eat. Certain surgical procedures like gastric bypass can also cause it by changing how quickly food moves through the digestive system. Rarer causes include inherited metabolic conditions and certain types of tumors.
Eating Patterns That Keep Levels Stable
The most effective long-term strategy for preventing low blood sugar is changing how and when you eat. Large meals with lots of simple carbohydrates cause a rapid blood sugar spike followed by a sharp drop. Smaller, more frequent meals that pair carbohydrates with protein and fat produce a slower, steadier rise.
Complex carbohydrates (whole grains, legumes, vegetables) convert to glucose over one to two hours, while protein takes three to four hours. Fat extends the effect even further. A meal that combines all three gives you a long, gradual release of energy rather than a spike and crash. If you’re prone to reactive lows after meals, this shift alone can make a significant difference. Aim to eat every three to four hours rather than going long stretches without food, and avoid sugary drinks or snacks on an empty stomach.
Managing Blood Sugar Around Exercise
Physical activity pulls glucose out of your bloodstream and into your muscles, which is great for overall health but can trigger a low if you’re not prepared. The risk doesn’t end when the workout does. Blood sugar can continue dropping for hours afterward as your body replenishes its energy stores.
Check your blood sugar 15 to 30 minutes before exercise. If it’s below 80 mg/dL, eat at least 30 grams of carbohydrates and wait 15 minutes before starting. If it’s between 80 and 180 mg/dL, a smaller snack of 15 to 30 grams of carbohydrates is typically enough. Above 180 mg/dL, you may not need a snack at all.
For workouts lasting longer than 30 minutes, plan to consume 15 to 30 grams of carbohydrates for every 30 to 60 minutes of activity. Good pre-exercise snacks combine carbs with protein or fat for sustained energy: a banana with peanut butter, crackers with cheese, a granola bar, or trail mix with nuts and dried fruit. After exercise, check your blood sugar every one to two hours and have a carbohydrate snack to prevent a delayed drop.
How Alcohol Affects Blood Sugar
Alcohol is one of the less obvious triggers for low blood sugar. Your liver normally releases stored glucose into your bloodstream between meals to keep levels steady. When you drink, your liver prioritizes breaking down alcohol and temporarily stops releasing glucose. This means a low can sneak up on you hours after drinking, especially overnight while you sleep.
The risk is highest if you drink on an empty stomach or if you combine alcohol with diabetes medication. Eating before and during drinking helps buffer the effect. If you drink in the evening, checking your blood sugar before bed and having a snack can reduce the chance of a dangerous overnight low.
Using Continuous Glucose Monitors
A continuous glucose monitor (CGM) is a small sensor worn on the body that tracks your blood sugar in real time and sends data to your phone or a receiver. The biggest advantage for preventing lows is the alert system: you can set the device to warn you when your glucose is trending downward or has crossed a threshold, giving you time to act before symptoms start.
These alerts are only useful if they actually reach you. The FDA has warned that smartphone settings like Do Not Disturb, Sleep Focus, Low Power Mode, and similar features can silently block alerts from CGM apps. If you use a CGM, make sure the app has permission to send notifications, use Bluetooth, and run in the background. Disable any power-saving or focus modes that could suppress alerts, particularly at night when you can’t feel symptoms while asleep.
When a Low Becomes an Emergency
Most lows are mild and respond well to the 15-15 rule. But severe hypoglycemia, where a person becomes confused, loses consciousness, or has a seizure, requires a different response. Someone in this state can’t safely eat or drink because of the choking risk.
Glucagon is a hormone that signals the liver to release its stored glucose. It’s available as an emergency kit (an injection or nasal spray) that a friend, family member, or coworker can administer. If you’re at risk for severe lows, keeping a glucagon kit accessible and making sure the people around you know how to use it is important. After receiving glucagon and regaining consciousness, the person should eat carbohydrates as soon as they’re able to swallow, to prevent the blood sugar from dropping again. If there’s no response within 15 minutes, a second dose can be given while waiting for emergency medical help.