Treatment of Hypoglycemia: Is the 15 g/15 m Rule Still Relevant?

People with type 1 diabetes (T1D) are familiar with the 15 g/15 m rule, as this is the current recommendation for treating non-severe hypoglycemia (with a blood sugar value < 4.0 mmol/L), i.e., that they’re able to treat on their own, without assistance.

There are as many causes of hypoglycemia (e.g., too much insulin, physical activity) as there are people with T1D: everyone is unique. With closed-loop insulin pumps (artificial pancreases) as a popular treatment option, is the 15 g/15 m rule still appropriate for all and in all circumstances? 

Canadian researchers have found that on average, treating one hypoglycemic episode takes more than 15 minutes and often requires more than 15 g of carbohydrates.

Why 15 g/15 m then?

This rule was established in the 1980s, when insulin was formulated differently and CGMs (continuous glucose monitors) didn’t exist yet. It’s based on the assumption that 15 g of fast-absorbing sugars should usually be enough to raise blood sugar within 15 minutes. It should allow the body enough time to absorb these carbohydrates and prevent an even greater drop in blood sugar levels and the onset of serious symptoms, such as loss of consciousness.

The 15 g/15 m rule is still recommended today, and the procedure is to be repeated every 15 minutes until blood sugar levels are back above 4 mmol/L.

Reality check: most people with T1D use more than 15 g of carbs to treat hypoglycemia 

In a 2016 study involving 121 adults with T1D, 78% of the participants had at least one hypoglycemic episode per day, and the average amount of carbohydrates they used to bring their blood sugar back into range was 32 g. In fact, 73% of the participants – particularly the younger ones and those with a greater fear of hypoglycemia – consumed more than 20 g of sugar, which was likely more than they needed. 

This analysis was the first to consider both the treatment of hypoglycemia and the choice of snacks used to prevent or treat low blood sugar.

The most common carbohydrates used to treat hypoglycemia were fruit juices or sweetened beverages (39%), as well as granola bars or candy (29%). 

Does treating hypoglycemia really take that long?

In 2018, a study involving 27 participants with T1D who used an insulin pump examined how effective an amount of 16 g of carbohydrates was to treat hypoglycemia. 

Only 38% of participants saw their blood sugar rise above 4 mmol/L within 15 minutes, and on average, it took 19.5 minutes for blood sugar levels to be back in range.

So, is it better to take more sugar to treat hypoglycemia more quickly and to avoid it dropping again? Research is ongoing to find an answer.

Should I take more sugar when my blood sugar is lower?

To answer this question, researchers recently compared how effectively hypoglycemia could be treated with 16 g or 32 g of sugar at two levels: between 3.0 and 3.5 mmol/L and below 3.0 mmol/L.  

The results show that only 25% of hypoglycemic episodes between 3.0 and 3.5 mmol/L were successfully treated within 15 minutes with 16 g of carbs, compared to close to 50% with 32 g. A second dose (i.e., 16 additional grams of sugar) was required for 50% of participants who initially took 16 g of sugar, and 15% of those who initially took 32 g.

The study also revealed that although 32 g of sugar seem more effective in treating hypoglycemia between 3.0 and 3.5 mmol/L, they’re still insufficient to treat hypoglycemia below 3.0 mmol/L within 15 minutes for 78% of the participants (78%).

Further studies will be needed to fully understand all the factors at play (e.g., the rate at which blood sugar drops) and the amount of sugar needed.

What about artificial pancreases?

Newer insulin pumps, sometimes called hybrid closed-loop systems or artificial pancreases, are able to suspend insulin delivery when blood sugar levels are dropping and approaching hypoglycemia. So, should the recommended amount of sugar to treat hypoglycemia be reduced? This is important to consider, as overtreating hypoglycemia will cause the opposite problem, hyperglycemia.

There is very little data on the treatment of hypoglycemia with the most recent pumps, so a study was recently conducted with people with T1D who use either a hybrid closed-loop system (e.g., Medtronic 770G, Tandem Control-IQ) or an experimental dual-hormone insulin pump combining insulin and glucagon.

The study found that only 45% of hypoglycemic episodes were successfully treated in less than 15 minutes with 16 g of sugar, while the average time was 21 minutes and involved taking more sugar. 

Therefore, in many cases, the current 15 g recommendations aren’t excessive for either type of pumps. 

Could taking carbohydrates earlier help to avoid hypoglycemia?

Another study was conducted to assess the need to take sugar before blood sugar drops below 4 mmol/L, since more than 16 g or 32 g of carbohydrates and more than 15 minutes are often required to get blood sugar levels back up. Hypoglycemia was induced by administering a bolus of insulin to 29 participants with T1D. Then, the participants were assigned a blood sugar threshold (5.0 or 4.5 or 4.0 mmol/L) where they took 16 g of sugar. 

The results have not yet been published, but current data highlight several important points for people with T1D:

• The earlier a drop in blood sugar is reversed, the better the chances that either hypoglycemia can be avoided, that the time spent in hypoglycemia can be reduced, or that the total amount of sugar taken and overtreatment-related hyperglycemia can be limited. 

• CGMs are particularly useful for detecting impending hypoglycemia with various alerts options and trend arrows. Alarms can be set at any point above 4.0 mmol/L, which allows the patient to preventively take carbs to avoid hypoglycemia. 

• It’s important to reflect on the current recommendations for treating hypoglycemia to make sure that people with T1D spend less time in hypoglycemia and don’t take carbs they don’t need. 

Further analysis needed

The majority of studies conducted to revise the 15 g/15 m rule consider many factors that can lead to hypoglycemia (e.g., correction bolus, overestimating meal carbohydrates), but still leave out some (e.g., hypoglycemia triggered while taking a walk). And there is little data on how the type of treatment (injections vs. pumps), gender, time of day, type of carbohydrates used (glucose tablets vs. juice) and active insulin might contribute. 

These multiple factors will need to be further studied in order to set more appropriate guidelines for the treatment of hypoglycemia. 

While the 15 g/15 m rule remains a useful and recommended guideline, recent research shows that it may be necessary to individualize treatment of hypoglycemia. 

References :

Savard, V. et al. Treatment of hypoglycemia in adult patients with type 1 diabetes: an observational study. Canadian Journal of Diabetes (2016) 40 (4): 318-23. DOI: 10.1016/j.jcjd.2016.05.008 

Gingras, V. et al. Treatment of mild-to-moderate hypoglycemia in patients with type 1 diabetes treated with insulin pump therapy: are current recommendations effective? Acta Diabetol. 2018; 55(3): 227-231. DOI: 10.1007/s00592-017-1085-8 

Taleb, N. et al. Non-severe hypoglycemia in type 1 diabetes: a randomized cross-over trial comparing two quantities of oral carbohydrates at different insulin-induced hypoglycemia ranges. Accepted in Frontiers Endo.

Taleb, N. et al. Efficacy of treatment of non-severe hypoglycemia in adults with type 1 diabetes using oral carbohydrates during automated insulin delivery with and without glucagon. Canadian Journal of Diabetes (2023). https://doi.org/10.1016/j.jcjd.2023.04.013

Cheng, R. et al. Towards prevention of non-severe hypoglycemia in people living with type 1 diabetes with oral glucose at a higher blood glucose level – The REVERSIBLE randomized controlled trial. Manuscript under preparation.