by IDS Director of Intensive Diabetes Management, Tavia Vital
Why Doesn't the Rule of 15 Work?
Most handouts for fixing hypoglycemia have an easy-to-remember title: The Rule of 15.
The Rule of 15 states that when a glucose level is low, we should eat or drink 15 grams of carbohydrates, then check blood sugar in 15 minutes to ensure the treatment is working. If the glucose is still low, the handouts instruct us to keep eating with 15 grams of carbs and re-checking every 15 minutes until the low glucose is gone. Some handouts even include an important tip: Eat or drink 15 grams of rapidly digesting carbs, or fast-acting carbs. Typically the handouts list options such as glucose tablets and other options such as 1/2 cup juice, 1/2 can regular soda, and perhaps the list may include raisins, a cup of milk, or graham crackers.
Although The Rule of 15 is easy to teach and easy to remember, there are several issues with the plan.
First, especially if a person has an automated insulin delivery system that reduces and suspends basal insulin, it will likely take less carbs to treat a low than 15 grams.
Next, what is listed on typical hypoglycemia handouts has a range of glycemic index from low, medium, and high. Low, medium, and high glycemic index items are all listed under the statement about taking "rapid digesting carbs" even though the foods and drinks listed are NOT rapidly digesting options.
Last, the actual amount of carbs needed to fix a low depends on several different factors.
With an automated insulin delivery system it may take 1/3 to 1/2 as many carbs to fix a low compared to what is needed for the same low if the person takes injections or uses a non-automated insulin delivery system. If your glucose is dropping rapidly, or if it is already very low and still dropping, it is important to choose an option that will digest fast to stop the drop fast.
What are the fastest digesting options to fix hypoglycemia?
- Glucose gel
- Then glucose powder
- Then glucose tablets
- Next, graham crackers
- Then raisins
- Then regular soda
- Then fruit juice
- Then low-fat milk
The glycemic index range of all of the listed options here is 110 to 20. The glycemic index of table sugar is 65, as a comparator.
The amount of carbs needed when a person is at rest is less than mid-exercise. The amount of carbs needed to fix a low when there is minimal to no rapid-acting insulin active in the body is less than when there is a lot of insulin active in the body.
If glucose is trending down slowly without much insulin on board and you are not physically active, it may work fine to pick a lower glycemic index option. If glucose is dropping rapidly or it is shortly after taking rapid-acting insulin, sticking with the highest glycemic index option you have available will keep you safe or help your glucose get back to a safe level quicker than the slower glycemic index options.
After taking a low glucose treatment, it is best to check glucose with a finger stick and not rely on the sensor glucose result. Keep in mind if the finger stick glucose is higher than the pre-treatment glucose, it is likely the glucose level will continue to rise until all of the carbs have digested from the treatments you chose. An easy mistake to make is to see a low glucose at the 15-minute recheck and think additional glucose is needed.
However, if the low glucose is higher than the pre-treatment glucose, keep in mind the lower glycemic index choices will continue to cause glucose to rise for well over an hour or longer. A higher glycemic index option will continue to cause a glucose rise for 30-60, possibly 90 minutes. If you treat until your glucose is at your target, you can count on a bigger upswing after as the carbs continue to digest over time.
Take the time to learn how quickly your go to treatment options work with a low where you do not have insulin on board. Watch carefully for about 2 hours after a low glucose treatment and see how long that treatment has an impact on your glucose levels. Watch to see how much glucose rise occurs with that treatment.
And throw out that Rule of 15 handout!
