Managing mealtimes using your hybrid closed loop system (HCL)

HCL systems automatically adjust insulin delivery and are aiming to keep your glucose levels between 3.9 - 10 mmol/L.  

If your glucose is dropping or is predicted to drop, the system will reduce or stop insulin delivery. If your glucose is rising or is predicted to rise, the system will increase insulin delivery or deliver a correction bolus.  

There are currently 4 different HCL systems. They all aim to keep you in range as much as possible. They do this in slightly different ways.  The way the systems work is often described as the algorithm.  

With all HCL systems, you need to tell the pump when you are eating by entering carbohydrate into the bolus advisor and delivering insulin (bolus).

Yes, it is important to tell the system when you are eating. HCL are less effective at managing rapid rises in glucose caused by missed boluses.  

Carbohydrate counting and delivering insulin before you eat will give you the best results.  

• It allows the system to know how much insulin you need and optimise the algorithm.  
• You will achieve a higher time in range.  
• It will reduce the risk of hypos after eating.

 Have a meal routine and remember healthy eating

Aim for 3 meals per day with only 1-2 small snacks throughout the day if needed.   

Try and leave a gap of at least 2 hours in between eating during the day. Try not to eat overnight. Having a balanced meal pattern with a period overnight without food is important for a healthy body weight. Leaving 2-3 hours between food also allows your glucose to return into range.  

Having a healthy, varied diet with plenty of wholegrains, fruit, vegetables, beans and pulses helps with diabetes management.  

Try to limit processed foods as these tend to be higher in refined sugar and less healthy fats.  

 Count your carbohydrates

We know that young people tend to be good at counting carbohydrates. Think about what part of the meal is carbohydrate and use the Carbs & Cals book or app to count the amount of carbohydrate you are going to eat.  

Try to be as accurate as possible.  

It is a good idea to recheck the carb count of the foods you eat regularly. As you grow your portions sizes will change. It is important to make sure your carb counts are up to date!  

 Bolus 10-15 minutes before eating

This is called pre-bolusing. It will reduce the glucose spike you might see after eating.    

Glucose spikes caused by late boluses can prompt the system to deliver more insulin than you need, so bolusing 10-15 minutes before eating also reduces the risk of hypos in the hours after you eat. 

If you use an ultra rapid acting insulin (eg Fiasp), bolus 5 minutes before eating. 

Pre-bolusing will help you spend more time in range.  

 Follow the bolus advice

The systems use previous insulin delivery, pump settings and your glucose trend to calculate your insulin dose at mealtimes and for corrections. Follow the bolus calculator to help the system work the best. 

 Unsure how much you will eat?

Sometimes you just do not know how much you are going to eat!   

Try bolusing for some of the carbs 10-15 minutes before eating. You can enter the rest of the carbs once you know what you will eat.  

 What happens if I forget to bolus?

It happens! If you forget to bolus, your glucose will start to rise. The system will try to help and increase insulin delivery.  

You can still bolus if you remember afterwards, you should adjust the bolus to reduce the risk of hypoglycaemia.

 Keep moving

Try to be as active as possible every day.   

Movement after meals can help glucose levels in the hours after eating.

If you are going to be active after meals, doing something that you know causes low glucose or hypos, then use the system to help out. See tips below.  

  What about high protein and high fat meals?

Meals that contain more than 30g fat or 40g protein can cause high glucose levels 3-5 hours after eating and may be tricky to manage.    

High fat and protein meals delay digestion and absorption of carbohydrate and cause some insulin resistance after the meal. Smaller amounts of fat or protein may impact the blood glucose levels of younger children.

High fat and/or high protein meals may require more insulin. 

The HCL systems will help manage your glucose in the hours after eating by responding to the rise in glucose and delivering more insulin. 

Even if you used a combination type bolus previously (dual wave or extended), try entering all the carbohydrate before eating and letting the system work. You can monitor your sensor glucose to see what happens.  

If there are meals that are more difficult to manage, please contact the dietitians and we can help.   

You still have the option to use an extended bolus. We suggest that you try to give all the insulin at the beginning to see if Control IQ can manage the glucose. If you decide to use the extended bolus, start with at least 60-70% upfront.   

If you are going to be active after meals, doing something that you know causes low glucose or hypos, then start the Exercise activity prior to the meal.

There is a safe meal feature which adjusts your meal bolus if the glucose is low or going down. The adjustment is made using the insulin delivery in the hours before you eat including corrections, autocorrections and any increased basal. It is important to follow the bolus calculator to avoid hypos. 

If you are going to be active after meals, doing something that you know causes low glucose or hypos, then set the Temp Target prior to the meal.

This system learns how to manage your glucose after meals, and it is normal to see the insulin delivery increase after eating.  

If the system suspends after you eat, this can lead to a glucose rise. In this situation, your carbohydrate ratio could be too strong.  

If you are taking a hypo treatment or having additional carbs for hypo prevention, enter the carbs in the Add Meal function, without delivering insulin. If your glucose starts to rise, the system will know why and only give insulin if needed.  

For high fat and/or high protein meals you can enter 60-70% of the insulin 10-15 minutes before eating. You can let the system manage the glucose after eating or you can add the rest into the Add Meal function.  

If you are going to be active after meals, doing something that you know causes low glucose or hypos, then increase your personal glucose target or use the Ease Off function prior to the meal.

If you are giving a second bolus at mealtimes, for second helpings or a dessert, do not use the sensor glucose for the second bolus. This will ensure the pump delivers the insulin for the carbs you are going to eat.  

If your glucose is above target in the hours after eating, you can give a correction bolus using the bolus calculator in the Controller. It is important to follow the bolus advice. If it doesn’t offer a correction, it is because the system has worked out that there is enough insulin on board.  

If you are going to be active after meals, doing something that you know causes low glucose or hypos, then start the Activity function prior to the meal. 

Please contact the diabetes dietitians at uclh.cddietitians@nhs.net if you would like a session to discuss managing glucose at mealtimes or activity and diabetes.

Emergency mobile: 07940 476811 

Email: uclh.cdorange@nhs.net or uclh.cddietitians@nhs.net 

Further information and fact sheets can be found on our Children and Young People’s Diabetes web page.