Pump Terms

Glossary letters

  1. 4 terms starting with A
  2. 6 terms starting with B
  3. 9 terms starting with C
  4. 6 terms starting with D
  5. 1 terms starting with E
  6. 2 terms starting with F
  7. 2 terms starting with G
  8. 4 terms starting with H
  9. 6 terms starting with I
  10. No terms starting with J
  11. No terms starting with K
  12. 2 terms starting with L
  13. 3 terms starting with M
  14. 2 terms starting with N
  15. 1 terms starting with O
  16. 6 terms starting with P
  17. No terms starting with Q
  18. 1 terms starting with R
  19. 6 terms starting with S
  20. 7 terms starting with T
  21. 1 terms starting with U
  22. No terms starting with V
  23. No terms starting with W
  24. No terms starting with X
  25. No terms starting with Y
  26. No terms starting with Z

Reference

  1. 01A to Z glossary

Explainers

  1. 02How an insulin pump works
  2. 03Pump or injections?
  3. 04Infusion sets and site rotation
  4. 05Carbohydrate counting
  5. 06Alarms and fail-safes
  6. 07Sick days
  7. 08Exercise
  8. 09School and nursery
  9. 10Travelling with a pump

Related reading

  1. 11Diabetes and the nervous system
  2. 12Official UK guidance

About

  1. 13About
  2. 14How we check facts
  3. 15Contact
  4. 16Privacy

Infusion sets, cannulas and site rotation

How the infusion set connects a pump to the body, where sets are commonly placed, why sites are rotated, and what UK sources say about problem sites and unexplained high glucose.

Updated 11 October 20265 min readGeneral information, not medical adviceBy the Pump Terms editors

Cross-section of the skin and the layer beneath it Three bands: the outer skin, the fatty layer just under it where a cannula rests, and muscle further down. A cannula enters at an angle and ends in the fatty layer. 1 2 3 4
Cross-section of the skin and the layer beneath it, not to scale.
  1. Outer skin
  2. Subcutaneous layer: the fatty tissue under the skin
  3. Muscle, deeper still
  4. Cannula: its tip rests in the subcutaneous layer

The pump holds the insulin, but the infusion set is what gets it into the body. If the set is working well, most people never think about it between changes. If it is not, the effects can show up quickly as high glucose readings, which is why UK sources spend so much time on it. This page covers what the parts are, where sets are commonly placed, why sites are rotated and when a site or set deserves attention. It gives general information only, and the person's own diabetes team has the final word on how to manage their own sets.

What an infusion set is

An infusion set is the part that carries insulin from the pump to the body. At its end is a cannula, which Diabetes UK describes as a tiny tube that goes just under the skin. Cannulas are changed regularly, as covered below. The overall picture of how it fits with the pump and cartridge is on the page about how an insulin pump works.

Diabetes UK describes two arrangements. With a tubed (tethered) pump, a small length of tubing connects the pump to the cannula, and the pump itself is carried on a belt, in a pocket or in a body band. With a tubeless patch pump, the pump sits directly on the skin where the cannula is placed and is controlled by a handheld device. Because patch pumps are disposable, Diabetes UK says the whole device is changed when the pump alerts you, not just the set and the location. The editors found no source they could open that compares finer design choices, such as steel against flexible cannulas, so this page does not describe them. The diabetes team and the manufacturer's instructions cover that detail.

Where sets are placed

Diabetes UK says people tend to put tubed pump sets and patch pumps on the upper legs, upper arms or stomach. An NHS resource from MyHealth London says most people prefer the abdomen, but that many places with a bit of padding can be used, such as the lower back, thighs, upper buttock or the back of the arms.

The same resource lists places to avoid:

  • "lumpy" or heavily used infusion sites;
  • areas where the skin folds;
  • directly on the beltline or under a waistband.

Diabetes UK says each manufacturer can have different advice on wearing a pump.

Why sites are rotated

Diabetes UK advises moving to a different place every time a cannula or patch pump is changed. The reason it gives is lipohypertrophy, where the body forms hard lumps that stop insulin working properly. Using the same site for too long can also cause itching and rashes, according to the same page. The practice of moving from one place to another is called site rotation.

MyHealth London gives a practical rule: the new site should be at least 5 cm away from the last one. It also notes that lipohypertrophy can still occur with a pump. For anyone using a hybrid closed loop, MyHealth London says it is particularly important to change the cannula regularly and use new sites each time, because those systems rely on good insulin absorption and a well-functioning cannula.

When sets are changed

Diabetes UK says a cannula or patch pump should be changed every two or three days. MyHealth London gives the same interval and the Chelsea and Westminster leaflet lists changing the infusion set regularly, every two to three days and ideally early in the day, among the factors that help people do well on a pump. The day-to-day name for this is a site change.

The MyHealth London resource also offers timing points. It suggests checking glucose one to two hours after inserting a cannula to be sure it is working, and not changing the set late at night before sleep, because a problem would go unnoticed and failure to absorb insulin overnight can result in diabetic ketoacidosis. It also suggests examining the cannula after removal for kinking or bending. The Chelsea and Westminster leaflet advises not going to sleep with unexplained high glucose that has not resolved, or within two hours of a new set change. Teams may give different instructions, and their advice takes priority.

Signs of a problem site

Diabetes UK says there is always a small risk of infection from the cannula. MyHealth London says that infusion sites are sometimes painful after insertion, that if a site is still painful one hour after set-up it is best to change the set and site, and that generally a set should be changed at the first sign of pain, redness or discomfort. It also recommends washing hands before opening packaging and before and after touching the old site to help reduce the chance of infection.

These sources do not describe how to treat an infected site, and this page does not either. Anyone who is worried about a site, or whose skin problems keep returning, should speak to their diabetes team. The Chelsea and Westminster leaflet says that anyone who keeps vomiting or cannot keep fluids down should go to hospital as an emergency.

Unexplained high glucose as a prompt to check the set

Diabetes UK says a set can become blocked or detached, which could lead to high blood sugar and increase the risk of diabetic ketoacidosis, so a set may need changing at short notice. It lists problems with the infusion set, cannula or pump failure as possible causes of unexplained high readings, and says to speak to the diabetes team for advice on when to check for ketones, because DKA can develop very quickly when a pump is not delivering the insulin needed. Blood ketones and what to do about them are covered on the page about sick days with a pump.

The Chelsea and Westminster leaflet lists questions to ask when glucose is unexpectedly high. They include whether there is an air bubble in the set, whether the cannula has slipped out because of sweat, whether there is a blockage or leak, whether the set has kinked, and whether it has been in for more than 72 hours. It also advises phoning the manufacturer's support line straight away if the pump may not be working.

Questions people ask

Is a patch pump changed in the same way as a tubed pump's set?

Not exactly. Diabetes UK says a patch pump is disposable and the whole device is changed when it alerts you, whereas with a tubed pump the set and site are changed while the pump itself stays.

Can lipohypertrophy happen with a pump?

Yes. MyHealth London lists it among the complications that can still occur with a pump, and Diabetes UK names it as the reason for rotating sites.

In short

An infusion set carries insulin through a cannula just under the skin, and UK sources describe changing it every two to three days and moving to a new site each time. Pain, redness or discomfort at a site, and unexplained high glucose, are reasons to act and to contact the diabetes team. Details of how to respond belong to each person's own care plan.