When your blood sugar drops below 70 mg/dL, eat or drink 15 grams of fast-acting carbohydrates immediately, then wait 15 minutes and check again. This simple approach, known as the 15-15 rule, is the standard treatment for mild to moderate low blood sugar. Most episodes resolve within minutes when you act quickly, but knowing what to eat, what to watch for, and what to do in more serious situations can make a real difference.
How to Recognize Low Blood Sugar
Low blood sugar, or hypoglycemia, announces itself with a cluster of symptoms that can come on fast. You might feel shaky, jittery, or suddenly hungry. Dizziness, lightheadedness, confusion, irritability, a racing or unsteady heartbeat, and headaches are all common. Some people notice blurry vision or have trouble speaking clearly. These are signs of mild to moderate hypoglycemia, and they mean your body still has enough function for you to treat yourself.
Severe hypoglycemia is a different situation. When blood sugar drops very low, your brain starts losing the fuel it needs to work. You may become unresponsive, lose consciousness, or have a seizure. At this stage, you can’t treat yourself, and someone nearby needs to step in.
Clinically, there are three levels. Level 1 is a reading between 54 and 69 mg/dL. Level 2 is below 54 mg/dL, the point where neurological symptoms kick in and you need to act right away. Level 3 is any episode severe enough that you need another person’s help to recover, regardless of the exact number on your meter.
The 15-15 Rule: Step by Step
If you can check your blood sugar and it’s below 70 mg/dL, or you’re feeling symptoms and can’t test, follow these steps:
- Eat or drink 15 grams of fast-acting carbohydrates. Good options include 3 glucose tablets, half a cup (4 ounces) of fruit juice or regular soda, 6 to 7 hard candies, or 1 tablespoon of sugar.
- Wait 15 minutes, then check your blood sugar again.
- If it’s still below 70 mg/dL, repeat. Have another 15 grams of carbohydrates and recheck after another 15 minutes.
- Once you’re back in range, eat a balanced snack or meal that includes protein and carbohydrates to keep your levels stable.
Glucose tablets or juice work best because they’re absorbed quickly. Foods high in fat, like chocolate, slow digestion and won’t raise your blood sugar as fast as you need. If you use an automated insulin delivery system (an insulin pump that adjusts doses on its own), you may only need 5 to 10 grams of carbohydrates unless the low is related to exercise or a meal dosing error.
What to Eat After You Recover
Getting your blood sugar back above 70 mg/dL is only the first step. Without a follow-up snack or meal, your levels can drop right back down. If your next meal is more than two hours away, eat a snack with slow-releasing carbohydrates and some protein. A slice of whole-grain bread with peanut butter, a piece of fruit with a handful of nuts, a cup of milk or yogurt, or a few oatcakes all work well. The goal is to give your body a steady source of glucose rather than another quick spike followed by another crash.
What to Do in a Severe Episode
If someone with diabetes becomes unconscious, unresponsive, unable to eat or drink, or starts having a seizure, do not try to put food or liquid in their mouth. They could choke. This is when glucagon becomes essential.
Glucagon is a hormone that signals the liver to release stored sugar into the bloodstream. It comes in two forms that someone nearby can administer. A nasal spray requires no preparation: you simply spray it into one nostril while holding the other closed. An injectable version comes either as a pre-filled pen (similar to an epinephrine auto-injector) or as a kit that needs to be mixed before injection into the thigh. Roll the person onto their side to prevent choking, and have someone call 911 while administering glucagon.
If you take insulin or medications that can cause low blood sugar, keep glucagon accessible and make sure the people you spend time with know where it is and how to use it. The nasal version is especially straightforward for bystanders with no medical training.
Common Causes of Blood Sugar Drops
Understanding why your blood sugar dropped helps you prevent the next episode. The most common triggers include:
- Too much insulin relative to what you ate or how active you were
- Not eating enough carbohydrates for the amount of insulin you took
- Insulin timing that doesn’t match when you eat
- Physical activity, especially if unplanned or more intense than usual
- Alcohol, which impairs your liver’s ability to release glucose
- Meal composition, since meals high in fat, protein, or fiber digest more slowly and may not raise blood sugar as expected
Some less obvious factors can also play a role: hot and humid weather, altitude changes, hormonal shifts during puberty or menstruation, and unexpected schedule disruptions. Nighttime lows are particularly common after a very active day, exercise close to bedtime, or drinking alcohol in the evening. If you wake up with a headache, feeling unusually tired, or with damp sheets from sweating, an overnight low may be the cause.
Driving and Safety Precautions
Low blood sugar and driving are a dangerous combination. Even after you treat a low and your blood sugar returns to normal, your thinking, reaction time, and coordination can remain impaired for 30 to 45 minutes. That means you should not get back behind the wheel immediately after treating an episode.
Check your blood sugar before you start driving. If it’s below about 90 mg/dL (5 mmol/L), eat a snack before you go. On long drives, recheck every two hours. If you feel symptoms while driving, pull over right away, turn off the engine, and treat the low before continuing. Wait at least 30 to 45 minutes after your blood sugar is back in range before driving again.
Keeping Supplies Within Reach
Low blood sugar can happen anywhere, and the faster you treat it, the less severe it becomes. Keep glucose tablets or a small juice box in your bag, your car, your desk at work, and on your nightstand. If you use glucagon, store it somewhere others can find it and check expiration dates regularly. Wearing a medical ID bracelet or necklace helps first responders and bystanders know what’s happening if you can’t speak for yourself. A few minutes of preparation makes the difference between a mild inconvenience and a medical emergency.