For most adults with diabetes, 15 grams of carbohydrates will raise blood sugar by roughly 30 to 50 mg/dL. That range is wide because the actual number depends on your body weight, how sensitive you are to insulin, what type of carbohydrate you eat, and whether you have food already digesting in your stomach. Still, this 15-gram dose is the standard starting point that the American Diabetes Association recommends for treating low blood sugar, precisely because it reliably produces a meaningful rise without overshooting.
Why 15 Grams Is the Standard Dose
The ADA’s “15-15 rule” is built around this number. When your blood sugar drops below 70 mg/dL, the guideline is to eat 15 grams of fast-acting carbohydrate, wait 15 minutes, then recheck. If your blood sugar is still low, you repeat with another 15 grams. The logic is simple: 15 grams is enough to push most people out of the danger zone without causing a rebound spike into high blood sugar territory.
Pure glucose is the preferred choice for treating lows because it enters the bloodstream fastest. Glucose tablets, glucose gel, and regular juice all work. The ADA specifically recommends avoiding foods high in fat or protein for this purpose, since fat slows digestion and protein can trigger additional insulin release, both of which delay the blood sugar correction you need.
What Changes the Size of the Rise
A smaller person will see a larger blood sugar increase from the same 15 grams. Someone who weighs 130 pounds has less blood volume to dilute that glucose into, so the concentration rises more steeply than it would in someone who weighs 220 pounds. This is also why children use a weight-based dose (typically 0.2 to 0.5 grams of glucose per kilogram of body weight) rather than a flat 15 grams.
Insulin sensitivity plays a major role too. If your body responds well to insulin, it will start clearing that glucose from the bloodstream quickly, limiting how high it peaks. If you have significant insulin resistance, the glucose lingers longer and the spike tends to be higher and more sustained. People with type 1 diabetes who have no insulin on board will see a steeper, longer-lasting rise than someone whose body is still producing some insulin.
The amount of active insulin already in your system matters as well. If you recently took a bolus dose and your insulin is peaking, those 15 grams may barely register because the insulin is pulling glucose out of your blood at the same time you’re adding it. This is one reason the 15-15 rule includes the recheck step: sometimes one dose isn’t enough.
The Type of Carb Makes a Real Difference
Not all 15-gram portions of carbohydrate behave the same way in your body. Simple carbohydrates like glucose tablets, juice, or regular soda are broken down almost immediately, producing a fast, sharp rise that typically peaks within 15 to 20 minutes. This is exactly what you want when treating a low.
Complex carbohydrates like whole grain bread, oatmeal, or beans take longer to digest because their chemical structure requires more breakdown before glucose enters the bloodstream. Fifteen grams of carbs from a slice of whole grain bread will raise your blood sugar more gradually, with a lower peak that stretches out over a longer period. The total glucose eventually delivered is similar, but the shape of the curve is flatter and wider.
The glycemic index captures this difference on a 0 to 100 scale. Pure glucose scores 100. White bread lands around 75. Lentils sit near 30. A 15-gram serving of a low-glycemic food might raise blood sugar by only 15 to 25 mg/dL at its peak, while 15 grams of pure glucose could push it 40 to 50 mg/dL in the same timeframe.
Practical Examples of 15 Grams
- Glucose tablets: 3 to 4 tablets (check the label, most are 4 grams each). Fastest option.
- Juice: About 4 ounces (half a cup) of orange or apple juice.
- Regular soda: About 4 ounces, not diet.
- Honey: Roughly 1 tablespoon.
- Raisins: About 2 tablespoons.
- Bread: One standard slice of white bread contains approximately 13 to 15 grams of carbs, though the rise will be slower than liquid sources.
If You Use an Insulin Pump or Automated System
People using automated insulin delivery systems (sometimes called closed-loop pumps) often need less carbohydrate to correct a low. The ADA notes that 5 to 10 grams is typically sufficient for these users, because the pump algorithm is already reducing or suspending insulin delivery as blood sugar drops. The exceptions are lows during exercise or situations where you significantly overestimated carbs for a meal bolus, which may still call for the full 15 grams.
Why Your Number May Differ
If you track your blood sugar with a continuous glucose monitor, you can learn your personal response to 15 grams by watching the pattern after treating a low. Over time, many people find their number is consistent enough to predict. You might discover that 15 grams reliably raises you 35 mg/dL, or that you need closer to 20 grams to get a solid correction. That personal data is more useful than any general estimate, because it accounts for your specific metabolism, weight, and insulin regimen all at once.
One thing to watch for: the urge to overtreat a low. When your blood sugar is dropping and you feel shaky, eating everything in sight is a natural response. But stacking carbohydrates before the first dose has time to work is the most common reason people end up with a rebound high in the 200s or 300s an hour later. The 15-minute wait is the hardest part of the rule, and also the most important.