Hybrid closed loop systems

Hybrid closed loop systems

A hybrid closed loop system, also known as an artificial pancreas, is an insulin pump system linked with a continuous glucose monitoring system that delivers variable automated basal insulin in response to real-time glucose levels. Many hybrid closed loop systems have an option to change the system settings for exercise.

The three most common hybrid closed loop systems in use at the moment are:

Tandem t:slim with Control-IQ 

Tandem t:slim with Control-IQ has an exercise mode which reduces insulin at higher glucose levels to avoid hypoglycaemia

Medtronic MiniMed 670G/770G

Medtronic MiniMed 670G/770G uses a temporary target in auto mode. The temporary target allows you to change the target blood glucose in auto mode

CamsAPS FX system

The CamsAPS FX system has an Ease-off mode when less insulin is needed. This could be at lower glucose levels or if glucose levels are falling rapidly

Hybrid closed loop systems are an area of developing diabetes knowledge and the various closed loop systems currently available are all slightly different.

Although the basic principles are described in this section, it is important that you discuss how you use the exercise settings for your hybrid closed loop system with your diabetes team. Additionally, the user manual for your hybrid closed loop system will explain features that may help you manage blood glucose levels during exercise.

General Guidance

Everyone responds differently to exercise and this guidance is just a starting point. You are likely to have to change things based on what happens when you exercise.

Bolus insulin

Adjust your bolus insulin in exactly the same way as described in the previous topic for pump users

Basal insulin

You may wish to use the exercise setting to change basal insulin delivery. The time of day that you exercise, the duration of exercise and the type of exercise you do will dictate whether to use exercise settings or not

The Impact of Different Types of Physical Activity

As discussed earlier in the course, different exercise types will affect your blood glucose differently and in turn affect how you may use a hybrid closed loop system.

Anaerobic physical activity

For anaerobic physical activity, there is no need to change hybrid closed loop system settings as anaerobic activity will tend to push your blood glucose up

Mild to moderate aerobic physical activity

For, mild to moderate aerobic physical activity, use the exercise settings as described below

High-intensity aerobic or endurance physical activity

Change your hybrid closed loop settings to manual (i.e. switch off the closed loop system) and use the principles described in the previous topic for pump users

Advice for Mild to Moderate Aerobic Physical Activity

Before exercise starts

If you are doing physical activity less than 90 mins after a meal:

Change your hybrid closed loop settings to manual (i.e. switch off the closed loop system) 60–90 minutes prior to physical activity and during physical activity and reduce your basal insulin by 50–80% (a 50% reduction is a good place to start)

If you are doing physical activity fasted or more than 90 minutes after a meal:

Switch on your exercise setting 90 minutes before starting to exercise

During exercise

Take extra carbohydrates as described in the ‘during exercise’ guidance in the ‘pump users’ topic. Monitor your glucose closely to guide your carbohydrate replacement (see ‘managing blood glucose during exercise’).

Caution: if you have the exercise setting off switched on and you take on extra carbohydrates and your glucose starts to rise, the hybrid closed loop system will increase the amount of insulin it delivers which may put you at risk of a hypo. You may need to adjust your carbohydrate intake to prevent this.

After exercise finishes

Switch back to standard hybrid closed loop – this should help avoid post-exercise hypoglycaemia

Be guided by experience – if you find that you do go hypo after exercise, consider keeping the exercise setting switched on. You may need to do this overnight if exercising after 4 pm or doing prolonged endurance activity


  1. Comment by Scott. M. on 14/10/2022 at 4:38 PM

    Ease-off mode reduces or stops insulin delivery at higher glucose levels or if glucose levels are falling rapidly

    -could you double check this
    – at high glucose levels it would increase insulin no?

    change to (please check im right kirsten)

    Ease-off mode reduces insulin delivery when you’ll need less and Boost mode increases insulin delivery when you’ll need more

  2. Comment by Scott. M. on 14/10/2022 at 4:42 PM

    i am finding this page very confusing – think we need to do a lot more hand holding as this stuff gets really complicated

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