To CGMS or not to CGMS?

By | 16 April, 2009

In 1994 when I was 14 years old I spoke at the British Diabetic Association 60th anniversary conference about my hopes for the future. I’d already had diabetes for 10 years by then. What did I want? The ability to see what my blood sugar was at any time without having to prick my finger.

Fast forward to 2009, I’m so close to 30 it’s undeniable; I’ve had diabetes for almost 26 years and I have such a device. It’s not as perfect as I’d dreamed but it’s the biggest leap forward in diabetes care that I’ve experienced.

Now for the techie bit – I use a Medtronic Paradigm combined insulin pump and continuous glucose monitoring system (catchy name, I know!).

If you look around on the web you’ll find loads of people talking about CGMS here and here and here – they seem to polarise opinion, people love them and hate them with equal passion.

I wouldn’t swap mine for the world, but there have been occasions when I could have happily thrown it out of the window. Here are the top issues I hear people complaining about:

  • CGMS readings are not identical to meter readings
    – this is because they are measuring different things (CGMS measures glucose in your interstitial fluid, not blood glucose) and there is approx 15 minute time lag. I don’t find it a problem, its not thatimportant whether you’re 4.5 or 5.5, the fact that you’re around a 5 and you can see which direction you’re heading in is enough. I’ve
    always found the trend to be accurate, i.e. whether I’m rising or falling.
  • CGMS can’t keep up with fast changes – I find it loses accuracy if you’re rising or falling very quickly – the sensor can’t keep up with the rapidly changing BG levels. For example, if I see that I’m 10 and rising really fast, I’ll always do a finger prick because it’s likely that I’m really around 14 and the sensor is lagging behind. Without the CGMS I wouldn’t have known I was rising in the first place, it alerts me to the need to do a blood test and check.
  • You still need to do blood tests – I still blood test around 3-4 times a day to calibrate the machine and to check any really low or high readings. In the first month or so I tested more. It takes time to learn when you can trust the readings and when they’ll be a bit out.
  • It takes time to get used to – from day 1 I’ve believed the benefits have outweighed the effort it takes to get
    used to the quirks of the system; however I do read about people who are disappointed because it isn’t perfect and takes some getting used to.

Now for the positives.

I really love my pump and CGMS and it has made a huge difference to my care. I’m aiming to keep my HbA1c in non diabetic range, i.e. below 6.2%. Before the best I could do was 6.5% but it was really hard work. I’ve been using the CGMS for 2 years and my HbA1c has been below 6% the whole time (and more importantly I’ve had a life too!)

So what do I love most?

  • The ability to see what my BG is at any time and take action accordingly.
    e.g. I’m in a meeting and see that I’m 8 and rising. I can take 0.5u of insulin and bring it back down to around 6.5. Previously I would have been unaware of what my BG was until I did a blood test hours later by which time I would have been above my target level for several hours. This makes it so much easier to get tighter control.
  • The ability to see your BG in context rather than as a one off reading.
    e.g. I see that I’m a 4. If that’s from a single blood test I have to eat to be sure I’m not going to go hypo. Now if I see I’m a 4 I can look at the history and see how fast I’m dropping, keep an eye on it for 15mins and see if it continues to drop or whether its actually bottomed out and I don’t need to take any action.
  • The reassurance of having the alarms means that I can be more aggressive with my control. I know that if I go low in the night I will get woken up and can do something about it. This is especially useful when I’m working away from home and am alone in a hotel room. Previously I was concerned about going hypo overnight so I
    ran my BGs slightly high when away from home. Now I have the confidence that the CGMS will alarm and I can eat something before things go too far.
  • The ability to spot the impact of certain foods.
    For some reason I go through the roof when I eat Special K breakfast cereal – I had no idea until I started using the CGMS. Now I don’t eat it any more. Previously I never took insulin 20mins before a meal, now
    I make sure I put some insulin in at least 20mins before because if I don’t, the post dinner peak on the CGMS is huge and if I make the effort to put the insulin in early I can really flatten out that peak. The pump of course makes a real difference there – I wouldn’t inject several times throughout a meal but with the pump I just push a button whenever I want some insulin.

So, why hasn’t everyone got one?

Firstly, it’s not a cure, its just another tool you can use to manage diabetes and it takes effort. Some people simply don’t want to be bothered with the amount of information a CGMS gives them. Fair enough.

Secondly, its new technology so huge levels of scepticism exist about whether it delivers long term benefits. Plus, not everyone (and that includes medics, patients, policy makers etc) is comfortable with new technology and many are reluctant to embrace it. My personal experience shows that it works for me, but we’re starting to see larger
research studies that show that it works for other people too – take a look here to see an overview of the research so far.

Thirdly, its perceived as being expensive. The actual pump/CGMS costs the same as a normal pump, but the sensors cost around £35 each. They’re licensed for use for 3 days each, but I use mine for 7 days and I know people who use them for longer. I’ve brought my HbA1c down significantly and sustained that over 2 years – that reduces my risk of
complications in the long term and therefore also the potential cost of those complications. We have to look at healthcare costs across a lifetime, not over a year. In short, in the immortal words of a well known hair care company, I use it because I’m worth it.

So, it’s not perfect and like all other aspects of diabetes care, you need to put some effort in to make it work but personally, I wouldn’t swap my CGMS for the world.

Category: Kit & equipment Tags: ,

About Alison

Diagnosed with Type One in 1983 at the age of four, Alison's been at this for a while now. She uses Humalog in a combined insulin pump and continuous glucose monitoring system and any blood glucose meter as long as it takes five seconds or less.

10 thoughts on “To CGMS or not to CGMS?

  1. Pingback: Show me the money | Shoot Up or Put Up

  2. patlovejoy

    I’d like to ask if you purchased your combined CGMS yourself as my Health Authority don’t issue them as yet. I have been seriously considering purchasing one as my BS is still very all over the place even with the use of an insulin pump – I actually test my BS at least 9 times a day – hence my considering purchasing one but I really don’t know where to start.

    Any help of where and how would be welcomed.

  3. Alison

    @patlovejoy Hi Pat. My pump and CGM are NHS funded after a long battle. Take a look at this post for some tips on securing funding –

    Most hospitals nowadays have a CGM that you should be able to borrow for a week. That would give you an idea of whether you like it and also some evidence to show that it works for you if you decide to push the NHS for funding. Try speaking to your clinic, or try one of the manufacturers (Medtronic, Dexcom or Abbott)to see if they could arrange a free trial.

    Feel free to email me if you’ve got more questions.

  4. Ross Timm

    I just got my CGMS starter kit and the online tutorial says in a few places that you must do a new sensor every three days.. I have heard from others that they use it for longer like yourself. The tutorial however says it will send an alert after three days and the only option they give to turn off the alert is to stop the sensor connection to the pump. I know they want to sell more sensors, but what is the trick to use the sensors for longer than three days? I currently use the infusion sets for two reservoirs also, even though they say you need to change them with every insulin reservoir (so every three days), again to save money.

  5. Alison

    @Ross Timm Hi Ross. I’m assuming you’re using a Medtronic CGM? If so, the sensor will automatically turn off after 3 days. If you go to “Sensor” then “Sensor start”, “New sensor” it’ll reactivate it for another 3 days (within a few minutes it’ll ask you for a calibration, then you’ll need to calibrate again within 6 hours, exactly the same as starting a new sensor).

    You can do the same again on day 6, however at day 7 it’ll stop working. At that point if you want to keep using the same sensor you need to disconnect the transmitter, put it on the charger for about 20 mins, reconnect and do the usual sensor start up process.

    Hopefully that makes sense, email me if it doesn’t!

    I tend to use my sensors for 6 days as I don’t like keeping them in my body for longer than that but I know people who get them to 14 days. has a lot of people using CGM and they’re full of handy tips.

  6. Tim

    I’ve just noticed you reveal your age in this article @Alison – I suppose this was the crazy sort of thing you did in your twenties…

    1. Alison Post author

      That’s not a problem, I’m content in the knowledge that I’ll never be quite as ancient as you @Tim 😉

  7. Pingback: Cheaper, non invasive, continuous glucose monitor could be around the corner | DIABETIC GLUCOSE WATCH

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