What does the pump do?

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I know a lot of people that are confused about what an insulin pump actually does for someone with diabetes.  How is it different to injecting yourself with the needle and syringe, why do you have to keep it attached to you all the time, does it mean that you are a poorly controlled diabetic, how does it go into your body? Are just some of the questions I have received.  Despite this, I am always happy to be asked questions and I do my best to answer them in a way that people without diabetes can try to understand.

I think a lot of people view these questions as an assault on what they are doing, but my impression, perhaps naively, is that it is just the nature of people to be curious and to ask questions as that is the only way that they can learn.

Insulin pumps are small, portable devices that deliver short acting insulin continuously over a 24 hour time period.  Every hour of every day the insulin pump delivers a small amount of insulin to the individual that it is connected to.  Using an insulin pump is different to other methods of diabetes management as you only use one type of insulin, short acting.  This would usually be Novo rapid or Humalog insulins.  These have their onset within 5-15 minutes and peak from 1-3 hours, they can last in the body for up to 5 hours but this is variable between individuals.  For me the onset is pretty quick, I would definitely say it is within 5 minutes and it usually peaks at about 1 hour and lasts 2.  Prior to using the insulin pump I used short and long acting insulin in different injections.  I did 40 units of long acting Lantus in the morning and I used humalog insulin throughout the rest of the day when I ate or when I needed to do a correction to get my blood sugars back to a good range.  In a day I would normally do about 6-12 injections, as well as numerous blood sugar checks.

When a person does not have diabetes, the body keeps enough glucose in the blood to maintain glucose levels between 70mg/dL and 120 mg/dL, this is considered to be the average blood glucose for people who do not have diabetes1 .  Glucose basically comes from foods that contain carbohydrates.  When you eat, food is broken down into nutrients such as glucose, these nutrients are absorbed from your stomach and small intestine into your bloodstream.  The bloodstream then transports this glucose and other nutrients around your body so you will be well nourished and have energy to function.  Glucose not used for energy immediately after eating is stored in the liver.  This stored glucose becomes a reserve fuel supply that is released back into the bloodstream when it is needed.  However, the body cannot use this fuel until the glucose moves into the cells of the body1.

Even though glucose moves freely from the digestive tract into the bloodstream it cannot move into most cells without the help of insulin.  Insulin is a hormone made by the pancreas which is severely depleted or nonexistent in people with type 1 diabetes.  Insulin’s primary role is to move glucose from the blood and interstitial fluid into cells.  When there is not enough insulin available, glucose cannot move into the cells.  Glucose would then build up in the blood and interstitial fluid causing blood glucose levels to be high1.

In a person without diabetes the pancreas monitors blood glucose levels closely and delivers precise amounts of short acting insulin to keep these levels stable.  Usually, the pancreas in a person who has type 1 diabetes is not working properly.  Diabetes is classified as an auto immune disease meaning that the body attacked itself for some reason or another, reducing or impinging that pancreas’s ability to make insulin.  This means that the glucose floating around in that person’s body either has a reduced ability or a completely nonexistent ability to transfer into the cells to provide energy.  This is the reason that when people are diagnosed with type 1 diabetes they can often be very lethargic, losing weight, passing large amounts of urine to try and get rid of the glucose and drinking lots of fluids in order to attempt to replenish these losses.


Prior to my diagnosis I was very lethargic which was completely out of character for me at the age of 10.  I had also been losing weight, was sporadically wetting the bed in the middle of the night and was very thirsty.  For 2 days I could not do anything but lie on the couch and watch TV until my mum took me to see our doctor where I was diagnosed with type-1 diabetes.


So now I use the insulin pump which basically acts as an external pancreas.  From years of experience and with the diabetes educator’s assistance when I first started using my pump we calculated the correct amount of insulin that I would need during different times of the day.  I had noticed that for the same amount of food I required more short acting insulin at dinner times in order to keep my blood sugar levels well controlled, this meant that my carbohydrate sensitivity and/or insulin sensitivity at this time was higher and lower respectively, we made these settings in my pump.  During the middle of the day my blood sugar levels compared to food eaten were most predictable so we made some guesses here and resolved to fiddle with the numbers.  Both insulin sensitivity and carbohydrate sensitivity can be changed numerous times throughout the day on the pump.  You can set a specific number to specific times which will coordinate with how your body reacts to these things

I have only ever used the Medtronic Paradigm Veo Minimed insulin pump; I have used this since the beginning of 2012.  There have been some hiccups along the way with the pump failing at times, but it has still been such a fantastic move for me and my career. Despite the occasional pump fail, as I have written about previously, it is a fantastic piece of machinery.

The pump delivers insulin in two ways; basal and bolus.  Basal insulin works similarly to the way the pancreas works generally in a 24 hour period.  Basal insulin basically means background insulin.  It is the insulin that is delivered to me over each hour of every day.  Similarly to the carb and insulin sensitivity’s, the bolus doses can be changed throughout the day to fit in with what the individual needs.  For some reason I need more insulin through the night than I need during the day, this is reflected in my basal insulin regime.  Throughout the day my basal insulin rates change slightly but these miniscule changes are essential to my ability to control my type 1 diabetes well.  See an example of my basal regime below.


People often wonder about sport and using an insulin pump.  Through my experience, the only time I have had an issue with sport and the pump is when I went for a run last week and changed the position of my pump.  Instead of having the pump clipped onto the outside of my sports bra this time, I had clipped the pump between my back and my bra.  This caused problems that I was not prepared for and I have now learnt my lesson not to do it again.  In terms of other sports, the insulin pump has never been a problem for me, it has never been knocked off and my blood sugars remain good dependant on my exercise and the particular settings I have made to compensate for these.  I have had lows sometimes after sport but no worse than while using insulin pens, and for me, lows with the insulin pump can be more easily resolved than with long and short acting insulin on board.


The Medtronic insulin pump is not waterproof so it has to be removed for swimming.  In this circumstance everything would normally be fine as long as you can monitor your blood glucose once in a while and the pump is not disconnected for more than two hours, as this is the active insulin time.  After this time the blood sugar level is more likely to rise as there will be no insulin within the system.  I have never had a problem with swimming and the insulin pump.  Despite having the pump detached, because I am swimming my blood sugar levels stay well controlled, and I am usually only disconnected for about an hour.  Similarly to other exercises, I would then reduce my temporary basal insulin rate thereafter depending on my blood sugar and what I am doing for the rest of the day.

The insulin pump also needs to be removed for a shower or a bath, but this is only usually for a short period of time so it is not a big problem.  Sometimes if I am going to read in the bath and have something to drink and a biscuit I will leave the insulin pump connected during my bath and clip it to the bin next to my bath and just be careful, it’s odd, but it’s true.  Either way I do it, I notice no real difference.  Disconnecting for half an hour to an hour is not a problem.


One of the really great things about the insulin pump is that for exercise you can set a temporary basal rate which takes into account what your current basal rate actually is.  For example, if I was planning on going for a run, I might set my pump at a temporary basal rate of 70% for 3 hours, I would aim to set this about 1 hour before my run.  This means that the pump will deliver 70% of my normal rate of insulin to me over those three hours and then it will default back to my normal settings.  Other times I don’t plan so far ahead so I just remove the pump completely to go for my run, this also works.  Following an unplanned pump run depending on my blood sugar, I would normally reduce my temporary basal rate to 50% for at least an hour and then reassess.

The other great thing about the temporary basal rate is reduction in hypoglycaemia.  If I feel like my blood sugar is going low, I can set my pump on a temporary basal rate of 0% for an hour.  Usually my blood sugar level will go up about 2-3 mmols/L after this hour and be back at a normal level thereafter.  One time when I have had the time to test before I set my temporary rate I was 3.8 mmols/L, I suspended for an hour then had dinner two hours later.  When I tested my blood sugar level at dinner time I was 5.8 mmols/L, at work this feature is often a life saver.

With the insulin pump I do bolus doses of insulin when I need them without injecting myself.  The insulin pump is particularly useful as it can do very specific amounts of insulin.  Bolus doses are measured in accordance with the amount of carbohydrates a person is eating, for example, if I were having 10 grams of carbohydrate (like with a biscuit) I would give myself 1 unit of insulin.  The amount of insulin varies with what type of food is eaten and varies for every individual person.  For example, something like sushi which is thought to be very healthy is also very high in carbohydrates because the rice is not low GI, I have to do a quantitatively large amount of insulin when I eat sushi compared to other foods; when my blood sugar is about 5 mmols/L to start with and I am having a meal of Japanese and/or sushi I would normally have to do about 8 units of insulin as a bolus.  A bolus dose of insulin is also used to make a correction in accordance with a high blood sugar level.

The Paradigm Veo Minimed also has some really great functions including square bolus and dual bolus which I will discuss in a blog soon to come!

I know a lot of people who thinking about using the pump may be concerned about where to put it and worried that it will fall off while they are working.  I have had someone tell me that there is no way they could use it because they are lifting heavy things all day and it would be knocked off if they dropped anything on it.  This is a fair statement, but if you are wearing your pump where it could be knocked off easily, you would be pretty silly.  There are numerous places someone can wear the insulin pump.  At work I clip it onto the side of my bra.  During the day I have it in the middle of my bra or clipped inside the pocket of my jeans.  If I am wanting the pump to be extra secure I will clip it to the inside of my underwear underneath my trousers or skirt.  I have only once or twice knocked the pump off and it was due to my own stupidity, by just accidentally dropping it from height while walking around the house without it actually attached to anything.  It’s frustrating but you do learn your lesson pretty quickly.  The pump comes with two clip attachments that you can use which are very secure in my experience.

When I’m away from the house I usually have a spare reservoir set and vial of humalog in the car so if the unexpected happens I am prepared to change my subcutaneous site. I have had to use this once at work when the humalog in my pump ran out faster than I expected, I was probably eating and bolusing too much!

The subcutaneous site for the insulin pump and the reservoir set needs to be changed when the insulin in the vial runs out; this is usually every 3 or 4 days.  I usually have the subcutaneous line in my abdomen but I have heard of people having them in their legs or arms without any problem.  I find that the insulin is better absorbed through my abdomen.  I tried the upper thigh once but found that the insulin was a little bit less effective than normal; again, this is specific to each individual.

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Sleeping with the insulin pump is simple; you can’t feel it inside you even if you are lying tummy down on the bed.  The insulin pump is only inconvenient when its owner is a roller in bed.  I however, often wake up with the pump wrapped around me but it has not fazed me at all.  I also frequently wake up with the pump tied in a couple of knots but this has never affected the delivery of insulin.  I have never managed to give myself a bolus dose of insulin in bed.  In order to give a bolus dose of insulin you need to press numerous buttons in a precise order so this is unlikely to happen by accident.


If anyone out there is considering using an insulin pump I would highly recommend it.  There are numerous choices you can make including which type of pump you would like according to what it is you want it to do for you.  There are waterproof pumps, pumps that have continuous glucose monitors attached, pumps that sync with your blood glucose tester and many other functions worth investigating.  Please send me any questions you may have, I am happy to help answer any you may have!  Don’t hesitate as you never know what great opportunities a change might bring!