If your blood glucose drops below 70 mg/dL, eat or drink 15 grams of fast-acting carbohydrates immediately, then wait 15 minutes and recheck. This simple approach, sometimes called the 15-15 rule, is the standard first response for low blood sugar and works for most mild to moderate episodes. What matters most is acting quickly, because blood sugar that keeps falling can progress from shaky hands to confusion, seizures, or loss of consciousness.
How to Recognize Low Blood Sugar
Your body sends two waves of warning signals as glucose drops. The first wave is driven by your nervous system’s stress response: trembling, a pounding heart, sweating, anxiety, sudden hunger, and nausea. These symptoms feel a lot like a rush of adrenaline, and they’re meant to push you toward food fast.
If blood sugar keeps falling, a second wave of symptoms appears because your brain isn’t getting enough fuel. You may notice poor concentration, confusion, weakness, drowsiness, blurred vision, headache, dizziness, or slurred speech. At this stage, decision-making gets harder, which is why it’s important to treat the early symptoms before they escalate. The CDC classifies anything below 54 mg/dL as severe low blood sugar, the point at which you may faint or have seizures and likely need someone else to help you.
The 15-15 Rule, Step by Step
The goal is to raise your blood sugar quickly without overcorrecting. Here’s how it works:
- Eat 15 grams of fast-acting carbohydrates. Good options include 3 glucose tablets, half a cup (4 ounces) of fruit juice or regular soda, 6 or 7 hard candies, or 1 tablespoon of sugar dissolved in water.
- Wait 15 minutes. Give the sugar time to reach your bloodstream.
- Recheck your blood sugar. If it’s still below 70 mg/dL, eat another 15 grams and wait again.
- Follow up with a balanced snack or meal once your numbers stabilize, to prevent another drop.
Glucose tablets are the most reliable option because they contain a precise dose and absorb fast. Juice and regular soda work well too. Avoid chocolate, peanut butter, or other foods high in fat, because fat slows digestion and delays the sugar from reaching your blood when you need it most.
When Someone Else Needs to Step In
Severe low blood sugar is a medical emergency. If someone is confused, having seizures, or has lost consciousness, they cannot safely swallow food or liquid. Do not try to put anything in their mouth.
Glucagon is the emergency treatment for this situation. It triggers the liver to release stored glucose into the bloodstream, and it works even when someone is unconscious. Three forms are available: a nasal spray that delivers powdered glucagon through the nose in one step (no needles), a pre-mixed pen similar to an EpiPen that’s ready to inject immediately, and a traditional kit that requires mixing a powder and liquid before injection. The nasal spray is the easiest for untrained bystanders to use correctly. If glucagon isn’t available, call 911 immediately. Even when glucagon is used, calling for emergency help is the right move if the person doesn’t wake up or respond within about 15 minutes.
Common Causes of Low Blood Sugar
For people with diabetes, the most frequent triggers are taking too much insulin, delaying or skipping a meal, or exercising more than planned without adjusting food or medication. Alcohol can compound the problem because it blocks the liver from releasing stored glucose.
Low blood sugar in people without diabetes is less common but does happen. Heavy drinking without eating is one cause. Prolonged fasting, severe malnutrition, or eating disorders like anorexia can deplete the body’s glucose reserves entirely. Certain serious illnesses, including severe liver disease, kidney disease, advanced heart disease, and severe infections, can also drive blood sugar dangerously low. Occasionally, someone takes a diabetes medication by mistake, which can cause a sharp drop even in a person with normal blood sugar regulation.
Why Some People Stop Feeling Symptoms
Repeated episodes of low blood sugar can train the body to stop sending those early warning signals. This is called impaired awareness of hypoglycemia, and it’s more dangerous than it sounds. Without the trembling, sweating, and hunger that normally alert you, blood sugar can plummet to severe levels before you realize anything is wrong. People with impaired awareness face a roughly sixfold increase in the risk of severe hypoglycemia.
If this has happened to you, meaning you’ve been surprised by a low reading without any preceding symptoms, glucose monitoring technology becomes essential rather than optional. A continuous glucose monitor (CGM) can catch falling levels and sound an alarm before you feel anything. For most people, setting the low alert between 70 and 75 mg/dL works well. During or after exercise, when drops are more likely, a higher threshold of 80 to 90 mg/dL provides an extra margin of safety. People in high-risk situations, like professional drivers, may benefit from alerts set between 80 and 100 mg/dL.
Preventing Repeat Episodes
Treating a low in the moment is only half the job. Preventing the next one requires understanding what caused this one. If you take insulin or a medication that can lower blood sugar, review the timing and dose relative to your meals and activity. A pattern of lows at the same time of day often points to a medication timing issue that’s straightforward to fix with your care team.
Eating regular meals and snacks helps keep glucose steady, especially before and after physical activity. If you exercise, checking your blood sugar before you start gives you a chance to eat a snack preemptively rather than scrambling mid-workout. Keep fast-acting carbohydrates with you at all times: in your bag, your car, your desk drawer, and your nightstand. The worst time to go looking for glucose tablets is when your hands are shaking and your thinking is foggy.
Make sure the people around you, whether that’s a partner, coworker, or friend, know where your emergency supplies are and how to use glucagon. Severe episodes don’t give you time to explain the instructions while they’re happening.