If your blood sugar drops below 70 mg/dL, eat or drink 15 grams of fast-acting carbohydrates immediately, then wait 15 minutes and recheck. This simple approach, known as the 15-15 rule, is the standard first response and works for most mild to moderate lows. But how you respond depends on how low your blood sugar is, what symptoms you’re experiencing, and whether the person having the low is conscious enough to swallow safely.
How to Recognize a Low
Low blood sugar produces two waves of symptoms. The first wave is your body’s adrenaline response: sweating, shakiness, a racing heart, anxiety, and sudden intense hunger. These symptoms are your early warning system, and most people learn to recognize them quickly.
If blood sugar keeps falling, a second set of symptoms appears as your brain starts running short on fuel. These include confusion, difficulty concentrating, blurred vision, weakness, dizziness, and behavior changes that can look like intoxication. In extreme cases, this can progress to seizures or loss of consciousness. Recognizing these stages matters because it determines whether you can treat yourself or need someone else to help you.
The 15-15 Rule: Your First Move
For a reading between 54 and 70 mg/dL (classified as a Level 1 low), the CDC recommends this straightforward process:
- Eat 15 grams of fast-acting carbohydrates. Good options include half a cup of fruit juice, 1 tablespoon of honey or sugar, or glucose tablets (check the label for the number that adds up to 15 grams).
- Wait 15 minutes. Resist the urge to eat more right away. Your body needs a few minutes to absorb the sugar.
- Recheck your blood sugar. If it’s still below 70 mg/dL, repeat the process with another 15 grams of carbs.
- Keep repeating until your blood sugar is back in your target range.
Once your blood sugar stabilizes, eat a regular meal or snack that includes some protein and complex carbohydrates. This helps prevent another drop in the next hour or two.
Why You Shouldn’t Overtreat
When you’re shaky and anxious from a low, the instinct is to eat everything in sight. But consuming too many carbohydrates at once can send your blood sugar surging well above your target range. Your body may also compound this by releasing its own rescue hormones (adrenaline, glucagon, cortisol, growth hormone), which trigger your liver to dump stored glucose into your bloodstream. The result is a frustrating spike that can last for hours. Sticking to 15 grams at a time, even when it feels like too little, prevents this rebound.
When Someone Needs Emergency Help
A Level 2 low (below 54 mg/dL) is more dangerous and requires urgent attention. A Level 3 low is any episode where the person is too confused, unconscious, or physically impaired to treat themselves. At this point, they cannot safely eat or drink because of the choking risk.
This is where glucagon comes in. Glucagon is a hormone that signals the liver to release stored sugar, and it’s available in three forms:
- Nasal spray: A needle-free device that delivers powdered glucagon through the nose. It works even on an unconscious person and requires no mixing or preparation.
- Pre-mixed pen: Similar to an EpiPen, ready to inject immediately into the outer thigh or upper arm.
- Mixed glucagon kit: Contains a powder and liquid that must be combined before injection. This takes more steps under pressure, so the other options are generally preferred.
If the person is unconscious, turn them on their side after giving glucagon to prevent choking if they vomit. Call emergency services for any episode involving loss of consciousness or seizure, even if the person seems to recover after glucagon.
Common Triggers to Watch For
Low blood sugar rarely happens at random. Understanding what caused an episode helps you prevent the next one.
The most common trigger for people with diabetes is a mismatch between insulin (or other glucose-lowering medication) and the amount of food eaten or energy burned. Taking your usual dose but eating less than normal, skipping a meal, or exercising more than expected can all tip the balance. Alcohol is another significant trigger. Heavy drinking without food prevents your liver from releasing its glucose reserves, which is why lows can strike hours after your last drink.
For people not on diabetes medication, prolonged fasting, malnutrition, or extended periods without food can deplete the glycogen stores your body relies on to maintain blood sugar between meals.
Exercise and Delayed Lows
One of the trickiest aspects of blood sugar management is that exercise can cause lows long after you’ve finished working out. There are two peaks of increased glucose demand after physical activity. The first hits roughly 60 to 90 minutes after exercise, when your muscles are restocking their energy stores and your cells are more sensitive to insulin. The second wave can arrive much later, with effects lasting up to 24 to 48 hours.
To reduce this risk, check your blood sugar before, during, and after exercise. Eating a snack with carbohydrates and protein about an hour beforehand helps. During longer sessions, 15 to 30 grams of carbs every 30 to 60 minutes can keep levels stable. Afterward, have a carbohydrate snack and consider reducing your insulin dose (if you use a pump, setting a temporary lower basal rate for one to two hours post-exercise can help). If you use a closed-loop insulin pump, switching to exercise mode handles some of this automatically.
Nighttime Lows
Low blood sugar that happens while you’re asleep is particularly dangerous because you can’t feel or respond to your symptoms. Signs that you or a partner might notice include restless or irritable sleep, sweaty or clammy skin, trembling, sudden changes in breathing, nightmares, and a racing heartbeat. Some people wake up with an unexplained headache or high morning blood sugar. That high reading can actually be the aftermath of a nighttime low, caused by your body’s hormonal rescue response overshooting and flooding your bloodstream with glucose.
Skipping dinner is one of the most common causes. If nighttime lows are recurring, the typical approach involves adjusting the dose or timing of evening medication. A continuous glucose monitor with low-alert alarms is one of the most effective tools here, checking your levels every five minutes and waking you if they start to drop. For people who experience frequent or severe nighttime episodes, this kind of monitoring can be a significant safety measure.
Driving and Safety
Always check your blood sugar before driving. If it’s below your target range, treat the low and wait until your levels are back to a safe number before starting the car. A low while driving can impair your reaction time, blur your vision, and cause confusion, all of which make it functionally similar to driving impaired. If you feel symptoms while on the road, pull over immediately, treat with fast-acting carbs, and don’t resume driving until you’ve rechecked and confirmed your blood sugar has recovered.
Keeping glucose tablets, juice boxes, or another portable carbohydrate source in your car, gym bag, and desk drawer means you’re never caught without a quick fix. If you take insulin or a medication that can cause lows, having glucagon accessible and making sure the people around you know how to use it can prevent a manageable situation from becoming a medical emergency.