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Have you ever noticed that you can eat the exact same food over and over again, but see your blood sugars react differently each time? This can sometimes be a frustrating reality for people living with type 1 diabetes, because there are so many factors that can affect after meal blood sugars. Glycemic index, accurate insulin dosing, dose timing and fat and protein content of your meals are just some of the factors your blood sugar levels after meals. Let’s take a look at these factors individually:

Glycemic Index

The Glycemic Index (GI) is a scale that is used to determine how quickly a food/beverage with carbohydrate will raise your blood sugar levels. Foods are ranked as high, medium or low on the GI scale.

1. High GI (70+): This group includes foods such as white rice, white bread, All Bran Flakes, rice cakes, soda crackers, potatoes etc. High GI foods are quickly digested and will raise blood sugar levels quickly, resulting in post-meal blood sugar spikes. You may find that your blood sugar peaks 30-60 minutes after eating these foods.

2. Medium GI (56 to 69): Foods in this group include pita bread, pumpernickel bread, rye bread, brown rice, basmati rice, rice noodles, couscous, instant oats etc. Your blood sugar may peak 60-90 minutes after having medium GI foods.

3. Low GI (55 or less): Most vegetables, beans and some grains including spelt bread, sourdough bread, steel cut oats, peas, corn, sweet potato and All Bran Buds are found here. These foods are digested much slower and therefore produce a smaller rise in blood sugar levels after 2 hours.


Lower GI foods help keep us full for longer because they are higher in fibre, and digest slowly. They can also help you maintain a healthy body weight. So, next time you cook pasta, leave it al-dente to keep it low GI or add lower GI grains or beans in your soups/stews. You can also find more information about Glycemic Index here:  Click Here

Accurate insulin dosing

Apart from the type of carbohydrates you eat, your bolus insulin dosing also plays an important role in determining your post meal blood sugar levels. How much insulin to take for a meal will depend on your Insulin to Carbohydrate Ratio (ICR). If your ICR is too weak or if you miscounted the carbohydrates in your meal, you may notice a significant rise in your blood sugar levels after eating.

Think you might need a refresher on carb counting?  Join us online for our carb counting workshop Click Here

Timing of insulin injection

It is also important to know when to bolus. Most rapid-acting insulins (including Humalog, Apidra and Novorapid), start working in 10 to 15 minutes and should therefore be taken about 15 minutes before eating.  Fiasp is an ultra rapid-acting insulin which starts to work in about 4 minutes, and can be taken right before eating. If you notice that high GI foods start to raise your blood sugar quickly, it may help to bolus further in advance to give the insulin a chance to start working before the high GI foods are absorbed into the bloodstream.

High fat/protein meals

Are you someone who finds it tricky to accurately dose your insulin for foods like pizza or steak? You’re not alone! These foods can be difficult to bolus for because protein and fats can cause a delayed rise in our blood sugar levels, several hours after eating.

Consuming 30g of protein in combination with carbohydrates or over 75 g protein taken by itself can cause blood sugar levels to rise. Protein can cause a delayed rise in the blood sugar levels (approx. 2-3 hours) and result in a peak in blood glucose after 5 hours. This spike is a result of a number of hormone related factors, like glucagon. High protein meals lead to increased glucagon levels in the body. Another contributing hormone is cortisol, which is increased in response to a high protein meal and leads to insulin resistance, resulting in higher blood sugar levels (1).

Higher fat meals such as pizza can slow down digestion and lead to a delay in the blood sugar peak. This can result in delayed high blood sugars, approximately 3 to 8 hours after consuming the high fat meal. This rise occurs because when the fat is digested by the body, it gets broken down to free fatty acids which increase your body’s resistance to insulin.

So, how can you bolus for these high fat or high protein meals? You may want to consider giving some of the bolus at the start of your meal, and delaying part of the bolus until later. This can help better mimic the natural rise and fall of blood sugars after eating these foods.

If you are someone who is using multiple daily injections, speak to your educator to learn more about how to bolus safely for these types of foods.

If you are using an insulin pump, you can try using the specialized bolus features in your pump:

Extended/Dual Wave: These specialized boluses allow for part of the bolus to be delivered immediately and the remaining to be spread out over a specified time period. If you are using the Omnipod or Tandem insulin pump, this specialised bolus is called an extended bolus. If you are using Medtronic, it is called the dual wave. If you’re not sure where to start, try giving 50% upfront, and 50% extended over 3-5 hours. You can customize the percentage of bolus you want to give and the duration, which you will learn more with experience. Using a Continuous Glucose Monitor (CGM) or Flash Glucose Monitor (FGM), can help you understand when the blood sugars start to peak, and you can adjust the percentage and duration accordingly.

Using specialized boluses can sometimes be complicated and challenging. For most people, it takes a couple of tries, and lots of blood sugar monitoring to figure out the right percentage and duration that works for them. Speak to your diabetes educator if this is something you’d like to review or get more support with!


References :

Paterson, M., Bell, K.J., O’Connell, S.M. et al. The Role of Dietary Protein and Fat in Glycaemic Control in Type 1 Diabetes: Implications for Intensive Diabetes Management. Curr Diab Rep 15, 61 (2015). Click Here

K.J.Bell, et. al. Impact of fat, protein, and glycemic index on postprandial glucose control in type 1 diabetes: Implications for intensive diabetes management in the continuous glucose monitoring era. Diabetes Care. 2015.38:1008-1015. Click Here