Hi Rob,
Welcome to the forum. Using CGM rather than finger pricking can become an expensive commitment and has sometimes displayed results that caused unnecessary alarm and consternation as T2 users of CGM find out their BG does all sorts of perfectly normal variations - that they weren't expecting! But CGM can be a useful and friendly way of getting a better understanding of how one's body responds to different foods and varying levels of activity and exercise.
@ColinUK did this and posted regular updates about his findings. I can't remember what his thread was called: I need to do a search (or hope he'll tell us).
My non-medically qualified recommendation is that Abbott's Freestyle Libre 2 is the best of the lower cost CGMs for your circumstances. Libre provides a 14 day single component sensor that reads and transmits; at the end of the 14 days the sensor is thrown away. Whereas it's competitor in the same price range, the Dexcom One, is a 10 day sensor but needs a 90 day transmitter. Once that transmitter is activated it can't be paused, so Dex One is most cost effective when used continuously for 90 days. For your purposes, if expense is a factor, you don't need to wear a CGM sensor 365 days a year.
For example you might wear a sensor for 14 days and find out certain BG behaviour patterns; then take a break and use some structured finger pricking to confirm that changes you are making or have made are remaining good for you; then resume with another sensor for a further 14 days - scrutinising a different aspect of food and activity. And so on. Also the 14 day periods with CGM can be timed to fit in with your needs; for example you might choose to wear a sensor while on holiday and likely to "indulge", so would like to monitor that period. Or the reverse, deliberately not wear a sensor when you know your lifestyle behaviour is going to be very different and pointless monitoring.
TRENDS not SPOT READINGS. In my opinion it is essential that you focus on trends, rather any "one-off" reading. With a CGM graph appearing as the sensor does its stuff, that is easy enough to do; you just have to resist over-reacting to a single reading and wait for the next sensor reading. But with finger prick readings there is a vulnerability to getting a rogue reading and it isn't necessarily apparent that the reading is rogue. Those of us who are insulin dependent tend to have a sense when a reading might be rogue and we will then wash our hands (or at least a finger!) and fp again; maybe even a 3rd time (we want to be sure that an abnormal reading is being correctly displayed since we may be making bolus insulin decisions on the basis of that abnormal reading).
But for identifying foods or activities that affect your BG you should be fairly systematic about the whole process. Typically take a reading shortly after waking and just as you go to bed, just to establish not only how much change in BG is happening overnight and while fasting - but also to get a longer term sense of where your BG is from day to day and week to week. Then for each meal take a spot reading just before the 1st bite then a 2nd reading 2 hrs later (the strategic readings that
@Leadinglights has referred to above). This is to see how your body has coped with that meal after 2 hrs. If doing that with fps 3 times daily is too intrusive then do it just for breakfasts, establish what breakfast foods work best for you and then do the same thing for your typical lunch meals. Then finally turn to your evening meals and thus systematically sort out what is right for you. From CGM graphs most of this food and activity scrutiny is effectively non-intrusive, whereas for fps it does involve some structure and needs commitment by you.
I suspect that after 6 or so seperate sensor periods you will know so much more about your BG behaviour that you'll find you will only want to wear a sensor most infrequently thereafter. This again lends itself to Libre 2; no contractual business involved - just buy sensors, from Abbott or a Pharmacy, when you need them. All CGMs need either a compatible mobile phone and an app or a Reader/Receiver which costs from £50 upwards. Libre seems to be more compatible with many phones than Dex One. The Libre app is better suited to recording meal carb values along with notes about what the meal was or changes made. The Dex One app I thought was poor for recording details you want to document, the BG readings provided by Dex One were fine.
If you come under the DVLA constraints of needing to finger prick before driving and then needing to carry a lancing device, meter and test strips in the car - those carrying constraints won't change. The DVLA will recognise and allow CGM readings both immediately before you drive and while driving, but you still have to carry the fp capability in the car. Also CGM is often not sufficiently accurate when you are out of the normal range of 4-10 mmol/L. CGM doesn't totally replace conventional fp testing.
Hope this is of some help.
