2021-07-11

Freestyle Libre vs Dexcom

I have used freestyle libre CGMs for a long time.

Yes, obviously, I’m diabetic, but I have always felt like a sort of amateur diabetic! I take one injection of slow acting insulin a day, not like real diabetics that have match a dose to what they eat every meal. I did not know imposter syndrome was a thing with diseases :-) However, having seen the CGM readings for a couple of non diabetics now I can see that my blood glucose is very different to “normal” and feel a tad more “legit”…

But not having to match insulin to every meal (I take tablets with meals to help) I’m not the normal target for a CGM. However, if you can afford them, I would recommend them for anyone who is diabetic even if like me it is more “mild”. Indeed, perhaps even more so where I cannot easily compensate for eating the wrong thing, the CGM has helped me get my diet right (on most days). My reaction to carbohydrates is far from obvious as some simple things can send my sugar spiking but others are no problem. The CGM helps me learn the problem foods and drinks, and what is not a problem. Even so, that is not always consistent, and can have surprises...

For example:-


  • The small hump on the left last night was an evening meal with loads of rice and vegetables.
  • The big spike in the middle was breakfast, which was a single sandwich (i.e. one slice of bread cut in two) and bacon, with a tablet even. No idea why so high!
  • The small hump on the right was a large roast beef dinner, vegetables, and even a nice cherry cheese cake with syrup - which I expected to be a "problem"...

Not an ideal day for sensible diet, but the effect is not anything like obvious from the meals!

However, one issue with the freestyle is they occasionally screw up and don't work. Yes, in theory, I could send them back, but it got so annoying I decided to try a Dexcom instead.

Freestyle libre

  • Each sensor lasts 14 days - means changing on same say of week.
  • Takes one hour to warm up at start.
  • Has to be scanned regularly, and only holds last 8 hours. Any older data lost if not scanned.
  • Works out around £25 a week.
  • The newest model has alerts for low/high but still needs scanning for readings.
  • Occasionally screws up and you waste a £50 sensor. Yes, could send it back.

Dexcom

  • Sensors lasts only 10 days.
  • Works out around £37 a week (on yearly plan).
  • Takes two hours to warm up at start.
  • Updates phone via Bluetooth so no scanning. Seems to catch up if not near phone for a bit, but no idea how much memory.
  • Has alerts for low/high, or soon to be low/high.

The actual sensors are different, the Dexcom has sensor and transmitter. It is bigger, has a bigger sticky patch, and thicker. The transmitter is silly - 3 month life limit and buy a new one (I included in above price), but seriously, in one off, it is £200! Why not 50p for a new button cell? And it is not like it is more complex that the whole freestyle sensor which is £50. Definitely some level of price gouging there, in my opinion.

Having said that, their web site makes no sense - you can buy packages, or individual sensors as it says "You can always choose to pay as you go, purchasing Dexcom products whenever you need them". However, the individual sensors say "Limit: 1 per user". So do they mean you can only buy "one at a time", or "one, ever". I assume "one at a time", but if that is the case the Starter pack (3 sensors and transmitter for £159) which says "Limit: 1 per user" would be the best deal of all, if it means "one at a time", so I have no idea!

The other thing that is interesting is the difference in the actual readings... Here is the last 24 hours on Dexcom and Freestyle.




The breakfast peak shows as 15.3mmol/l on the Dexcom, and under 13 on the Freestyle. The dips over night (that caused an alarm) shows as 3.1mmol/l on the Dexcom, and nearer 4 on the freestyle.

Scaling and overlaying you can see they are close, but not quite the same.

Problems!

The sensor lasts 10 days, well should do. I managed 5 days before it was too painful, and I removed it. The start pack has three, so I'll try one on my arm, but if that does the same I'm going to ask for a refund. Never had this with the FreeStyle Libre.

FYI, a week later this is still not healed properly - it is getting there but pretty serious reaction. I tried on my arm, and whilst the reaction was a lot less severe, I had to remove it as it was too irritating after a few days.

Dexcom are being slow to do anything. I've filed an MHRA report anyway.

7 comments:

  1. Looks like the battery is sort of replaceable, with some Dremel work!

    https://seemycgm.com/2018/07/12/g6-transmitter-battery-replacement/

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  2. That last picture looks like what I've seen with some people who are mildly allergic to the adhesive. Might want to try a different sticky patch to the one it is supplied with.

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    Replies
    1. That's not an option - this is not a separate "sticky patch", it is what is attached to the sensor module.

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    2. Looks very similar to what happens if I wear those white hypoallergenic plasters on any soft skin (inside side of arms, neck etc).

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    3. What I meant was that some people have cut a different plaster to shape and then stuck the sensor to that so that it acts as a barrier between the sensor's glue and their body. Bit of a hack, but until Dexcom reformulates their glue like Abbott did a few years back it is the only option for people who want to use that sensor have have a reaction.

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  3. Type2 on pills. I buy the Libre every now and then to keep me motivated. What it has taught me is breakfast is where the damage is done and doing some activity after breakfast is important. Evening meals are far less damaging.

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