If your blood sugar is low, eat 15 grams of fast-acting carbohydrates immediately, then wait 15 minutes and recheck. This is called the 15-15 rule, and it’s the standard first response for mild to moderate low blood sugar. Most episodes resolve quickly with the right food, but knowing the full picture, from recognizing symptoms to preventing a second drop, helps you handle it safely every time.
Recognizing the Signs
Low blood sugar (hypoglycemia) produces two distinct waves of symptoms. The first wave is physical: your body releases stress hormones that cause sweating, trembling or shaking hands, a racing heartbeat, nausea, anxiety, and sudden hunger. These are your early warning signals, and acting on them quickly is key.
If blood sugar continues to fall, a second wave of symptoms appears as your brain loses its fuel supply. These include headache, blurred or double vision, confusion, difficulty speaking, agitation, and extreme fatigue. At this stage, thinking clearly becomes harder, which is exactly why it’s important to act during the first wave when you still can. In older adults, a severe low can mimic stroke symptoms like one-sided weakness or slurred speech.
The 15-15 Rule: Your First Move
As soon as you feel symptoms or your meter reads low, eat or drink 15 grams of simple carbohydrates. Then wait 15 minutes for the sugar to reach your bloodstream, and test again. If your blood sugar is still low, repeat with another 15 grams. Keep repeating until your level comes back to a safe range.
Good sources of roughly 15 grams of fast-acting carbs include:
- Glucose tablets: 3 to 4 tablets (check the label, as brands vary)
- Fruit juice: half a cup of unsweetened juice
- Hard candy: 3 pieces
- Regular soda: half a cup (not diet)
- Honey or sugar: about 1 tablespoon
Avoid chocolate bars, cookies, or ice cream. The fat in these foods slows digestion, which means the sugar takes longer to hit your bloodstream. You need something that works fast.
Preventing a Second Drop
Once your blood sugar is back in a normal range, the job isn’t done. If your next meal is more than an hour away, eat a small snack that combines complex carbohydrates with protein and healthy fat. This combination slows digestion and creates a gradual, steady rise in blood sugar instead of another spike and crash.
Nuts are an ideal choice because they deliver all three (carbs, protein, and fat) in one handful. Other good options include whole-grain crackers with cheese, peanut butter on toast, or yogurt with fruit. Eating smaller meals or snacks every two to four hours also helps keep blood sugar stable throughout the day, especially if you’re prone to repeated lows.
When It Becomes an Emergency
Severe hypoglycemia is a medical emergency. If someone with low blood sugar loses consciousness, has a seizure, or can’t swallow, they cannot safely eat or drink anything. Do not try to put food in the mouth of someone who is unconscious.
If you have a glucagon kit, use it. Glucagon is a hormone that signals the liver to release stored sugar into the bloodstream, and it works even when someone can’t eat. It’s available as a nasal spray (for ages 4 and up) or as an injection. The nasal version is faster and easier for bystanders to use correctly. Studies have found that people administering the injectable version often make mistakes, like forgetting to mix the powder with the liquid or failing to remove air from the syringe, while errors with the nasal spray are less common.
Call 911 if the person doesn’t regain consciousness, if you don’t have glucagon available, or if you’re unsure how to use it. Stay with the person and turn them on their side to keep their airway clear.
Driving and Other Safety Concerns
Low blood sugar and driving are a dangerous combination. Diabetes Canada guidelines recommend not getting behind the wheel if your blood sugar is below 4 mmol/L (72 mg/dL). Even after you’ve treated a low and your levels have come back up, you should wait at least 40 minutes before driving. Your brain needs time to fully recover, even after your blood sugar readings look normal again.
The same caution applies to operating machinery, swimming, or any activity where impaired judgment or coordination could be dangerous. If you feel a low coming on during any of these activities, stop what you’re doing and treat it first.
Keeping Yourself Prepared
The best way to handle a low is to have supplies within arm’s reach before it happens. Keep glucose tablets or juice boxes in your car, at your desk, in your gym bag, and on your nightstand. If you use insulin or take medications that can cause lows, talk to your care team about whether a glucagon kit makes sense for you, and make sure the people around you know where it is and how to use it.
Wearing a medical ID bracelet or necklace can also be critical. If you’re ever unable to communicate during a severe low, it tells first responders what’s happening and speeds up treatment. A few seconds of preparation on a calm day can make a real difference during an emergency.