If your blood sugar drops below 70 mg/dL, eat or drink 15 grams of fast-acting carbohydrates immediately. This is the core of what’s known as the 15-15 rule: consume 15 grams of carbs, wait 15 minutes, recheck your blood sugar, and repeat if it’s still under 70. Most people feel noticeably better within 10 to 15 minutes of taking that first dose of sugar.
The 15-15 Rule Step by Step
The goal is to bring your blood sugar back into your target range without overshooting into high blood sugar territory. Here’s the process:
- Eat or drink 15 grams of fast-acting carbs. Options include 4 ounces (half a cup) of juice or regular soda, 1 tablespoon of honey or table sugar, 3 to 4 glucose tablets, 6 Life Savers candies, or 1 tube of glucose gel.
- Wait 15 minutes. Give your body time to absorb the sugar.
- Recheck your blood sugar. If it’s still below 70 mg/dL, repeat with another 15 grams of carbs.
- Once you’re back in range, eat a balanced snack or small meal that includes protein and complex carbohydrates to keep your levels stable.
That follow-up snack matters more than people realize. Fast-acting sugar enters and leaves the bloodstream quickly, so without something more substantial behind it, you can dip right back down. A handful of crackers with peanut butter, cheese and whole-grain bread, or a similar combination works well.
Why Sticking to 15 Grams Matters
When your blood sugar is low, the instinct is to eat everything in sight. That urge is powerful and hard to resist, but overloading on carbs creates a problem called rebound hyperglycemia, where your blood sugar crashes low and then spikes high. Research shows this “glycemic roller coaster” is associated with increased oxidative stress and cardiac strain, and people who habitually overcorrect their lows tend to overcorrect their highs too, creating a cycle of wide glucose swings.
People who experience more than four of these rebound spikes in a two-week period tend to have worse overall glucose control, with wider swings throughout the day. The fix is straightforward: measure out your 15 grams, set a timer for 15 minutes, and resist the urge to eat more until you’ve rechecked. It takes discipline in the moment, but it prevents a much bigger swing later.
Recognizing the Symptoms
Low blood sugar produces two waves of symptoms. The first wave comes from your body’s adrenaline response: shaking, a pounding or racing heart, anxiety, sweating, and sudden intense hunger. These are your early warning signs, and treating at this stage is easiest.
If blood sugar keeps dropping, the second wave hits. These symptoms come from your brain not getting enough glucose and include confusion, difficulty thinking clearly, weakness, fatigue, a sensation of warmth, and in severe cases, seizures or loss of consciousness. Severe hypoglycemia, defined as blood sugar below 54 mg/dL, is a medical emergency. At that point, the person may not be able to treat themselves and needs help from someone nearby.
What to Do in a Severe Episode
If someone with low blood sugar becomes unconscious or is having a seizure, do not try to give them food or liquid. They could choke. This is when glucagon is needed. Glucagon is a hormone that signals the liver to release stored sugar into the bloodstream, and it’s available as a nasal spray (brand name Baqsimi) or as an injection kit. The nasal spray doesn’t require any mixing or needles. You simply insert the device into one nostril and press the plunger.
If you take insulin or medications that can cause low blood sugar, talk with your doctor about having a glucagon kit and make sure the people around you, at home and at work, know where it is and how to use it. After glucagon is given, call for emergency medical help.
Common Causes of Low Blood Sugar
For people with diabetes, the most common trigger is a mismatch between insulin (or other glucose-lowering medication) and the amount of food eaten or physical activity performed. Skipping a meal, eating less than planned, or exercising harder or longer than usual can all tip the balance. Alcohol is another significant cause because it blocks the liver’s ability to release stored glucose into the bloodstream. This effect can last for hours, which is why low blood sugar sometimes strikes in the middle of the night after evening drinking.
People without diabetes can also experience hypoglycemia, though it’s less common. Causes include liver or kidney disease, adrenal or pituitary gland problems, excessive alcohol consumption, anorexia nervosa, and certain medications like some antibiotics and blood pressure drugs. Gastric bypass surgery can also trigger low blood sugar in the hours after eating, though the exact mechanism isn’t fully understood.
Preventing Lows During Exercise
Physical activity burns glucose, which is normally a good thing, but for people on insulin or certain diabetes medications it creates a real risk of going low. The timing of your last insulin dose matters a lot. If you exercise within 90 minutes of taking rapid-acting insulin, you’ll likely need to reduce that dose based on how long and how hard you plan to work out. For a 30-minute moderate workout, cutting the dose by about half is a common guideline. For 60 minutes of moderate activity, the reduction may need to be around 75%.
If your pre-exercise blood sugar is below 90 mg/dL, eating 10 to 30 grams of fast-absorbing carbohydrates before starting can help prevent a drop. For longer sessions over two hours, plan to eat additional carbs at roughly one-hour intervals, around 0.5 to 1.0 grams per kilogram of body weight. For a 150-pound person, that’s roughly 35 to 70 grams per hour. If you’re on oral medications where adjusting the dose on the fly isn’t practical, eating a carbohydrate-containing snack between meals on exercise days is a simpler prevention strategy.
Keeping Quick-Sugar Foods on Hand
The most important thing you can do to prepare for a low is to always have fast-acting carbs within reach. Keep glucose tablets or a juice box in your bag, at your desk, in your car, and on your nightstand. Glucose tablets are particularly convenient because they’re pre-measured (each one is typically 4 grams of carbs), they don’t melt or expire quickly, and they’re less tempting to snack on than candy.
Avoid using chocolate, cookies, or ice cream to treat a low. The fat in these foods slows digestion and delays the sugar from reaching your bloodstream. You want pure, fast-absorbing carbohydrates: juice, regular soda, honey, table sugar, hard candy, or glucose tablets.
Using a Continuous Glucose Monitor
Continuous glucose monitors (CGMs) can alert you before your blood sugar actually reaches a dangerous level. These devices measure glucose levels every few minutes and display real-time trends, so you can see if you’re dropping and how fast. Some systems offer predictive alerts that warn you up to 60 minutes before your glucose is expected to cross a low threshold. That advance notice gives you time to eat a small snack and prevent a full low rather than treating one after it’s already started.
Many CGM systems also allow you to share alerts with family members or caregivers via text message, which adds a safety net if you experience lows overnight or have reduced awareness of your symptoms. Over time, some people who experience frequent lows develop what’s called hypoglycemia unawareness, where the early warning signs like shaking and sweating become muted. For those individuals, a CGM with predictive alerts can be especially valuable.