Low glucose · 15-15 rule
15-15 rule timer, recheck in 15 minutes.
Start the countdown after you have treated a low glucose with fast carbohydrate. When it ends, recheck your glucose. A timer only: it cannot tell you your glucose or what to do for a severe low.
Timer
What the 15-15 rule says
NIDDK says: if your blood glucose is below your target or less than 70 mg/dL, eat or drink 15 to 20 grams of glucose or carbohydrates right away, wait 15 minutes and check again, and if it is still low eat or drink another 15 to 20 grams, checking again after another 15 minutes and repeating until your glucose is back in your target range. The American Diabetes Association’s standards likewise say glucose is the preferred treatment in conscious people below 70 mg/dL (3.9 mmol/L) and to re-test and re-treat, if needed, after 15 minutes. This timer counts those 15 minutes and keeps a round count.
Examples NIDDK gives for 15 to 20 g. Four glucose tablets or one tube of glucose gel; 1/2 cup (4 ounces) of fruit juice that is not low-calorie or reduced-sugar; 1/2 can (4 to 6 ounces) of regular soda; 1 tablespoon of sugar, honey or corn syrup. If your next meal is more than 1 hour away, NIDDK suggests a snack such as crackers or a piece of fruit.
Worked example. Glucose reads 62 mg/dL. You treat with 15 to 20 g of carbohydrate and press start at 15:00. At 00:00 the timer announces the recheck. If the new reading is still below your target, press “Still low” for round 2 and treat again. The page never sees your readings.
Severe lows. NIDDK says glucagon is the best treatment for severely low blood glucose, that people around you should call 911 right away after giving it or if no kit is available, and that you should plan this with your care team. Your own plan may differ from the general 15-15 rule, so follow what your care team told you.
Frequently asked questions
What is the 15-15 rule?
If glucose is below your target or under 70 mg/dL, eat or drink 15 to 20 grams of carbohydrate, wait 15 minutes, check again, and repeat if it is still low.
What counts as 15 to 20 grams of carbohydrate?
NIDDK lists four glucose tablets, one tube of glucose gel, 1/2 cup of regular fruit juice, 1/2 can of regular soda or 1 tablespoon of sugar, honey or corn syrup.
What if my glucose is still low after 15 minutes?
Per NIDDK, eat or drink another 15 to 20 grams, check again after 15 minutes and repeat until your glucose is back in your target range.
What if someone cannot treat a low themselves?
Do not use this timer. NIDDK says glucagon is the best treatment for severely low glucose, and bystanders should call 911 right away after giving glucagon or if there is no kit. Follow your own care plan.
Sources
Checked
- NIDDK: Low Blood Glucose (Hypoglycemia)
- American Diabetes Association: Section 6, Glycemic Goals and Hypoglycemia, Summary of Recommendations (Clinical Diabetes, 2025)
Runs entirely in your browser. Nothing you type is sent or stored.
Educational worked example, not medical advice
This page shows arithmetic and published rules of thumb for learning. It is not a dosing instruction, a diagnosis or a treatment plan, and it does not know your insulin, your body or your health history. Never change insulin or medicine because of a number on this page. Confirm every setting and target with your diabetes care team. If you have symptoms of a very low or very high glucose, follow your care plan; in an emergency call your local emergency number.