Libre 2 target glucose range for prediabetes

[Calderbloke]

Hi all,

I think I'm starting to get up to speed on getting to grips with BG monitoring using a Libre 2 CGM and a T200+ BGM. However, conversion between measurement units is causing me problems, and I'm trying to figure out how to set my target range on the Librelink app (Android) for my prediabetes, initially at 42mmol/moL. I've currently set it to 3.9 - 6.0 mmol/L based on various sources around the 'Net but obviously I,'d like to do it right!

 

[IanBish]

I set my upper limit at 8.5 mmol/L, which is the recommended maximum (after food) for those with diabetes. I'm not sure what the upper limit would be for pre-diabetes. Hopefully someone will know the answer.

 

[Rachox]

Mine setting are similar to @IanBish , 3.9 - 8.0.

 

[Calderbloke]

Mine setting are similar to @IanBish , 3.9 - 8.0.

Thanks to both - that looks more realistic and it also allows me to eat

 

[HairySmurf]

I also use 3.9 to 8 mmol/L as my target range. There's very little information out there on what constitutes normal, 100% healthy blood glucose levels as large-scale studies using CGMs in non-diabetics have not been completed yet. The only studies I know of were small-scale and did not follow the participants in the long-term to see who went on to develop health problems and who didn't.

This study is one I find easiest to interpret - Link - 80 people wearing CGMs for 12 weeks with an average HbA1c of 5.2% - 33 mmol/mol. There were some prediabetics in the group though the average HbA1c shows that the majority had no known issues.

"Participants reaching at least 7.8 mmol/l spent a median of 31 min/day (range 0–412 min) above this IGT (Impaired Glucose Tolerance) level. A quarter of the total cohort experienced glucose levels above this threshold for at least 75 min/day, and three individuals (3.8%) remained in this range for 5 h or more per day. These three individuals had HbA1c levels in the normal range (5.4–5.7%) and mean FPG between 4.9 and 6.5 mmol/l. The eight individuals who spent more than 2 h above the IGT cut-off had higher mean HbA1c (5.7%), FPG (6.1 mmol/l), age (55 years) and BMI (women 29 kg/m2, men 30 kg/m2) than those who did not. The proportion of non-white participants and women (six of eight for both) was higher than in the whole study population. Seven persons (9%) reached 11.1 mmol/l, with two individuals spending more than 1 h/24 h above this diabetic level."

"We found that nearly all individuals without diabetes exceeded the IGT threshold of 7.8 mmol/l (140 mg/dl) at some point during the day and spent a median of 26 min (range 0 min to 6 h 52 min) per day above this level. We also found that one in ten individuals reached diabetic levels (11.1 mmol/l, 200 mg/dl). These findings suggest that glucose levels in persons without diabetes frequently reach IGT range concentrations and that a considerable proportion reach diabetic levels. Previous smaller studies have suggested similar patterns, albeit in more homogeneous populations. A study in 32 individuals with confirmed normal glucose tolerance found that seven participants (22%) reached glucose concentrations above 11.1 mmol/l (200 mg/dl) during an average of 28 days of CGM and that participants spent on average 42 min/day at glucose concentrations above 7.8 mmol/l (140 mg/dl)"

Those figures suggest that somewhere around 7.8 mmol/L is a natural threshold that a few people never cross at all but which is the typical healthy maximum for most people, while a significant number of people with normal HbA1c results can 'spike' to levels quite a bit higher than that. Other studies like that one show similar results and so I aim to stay below 8 mmol/L most of the time while not worrying too much about going a little above that level after maybe two or three meals per week so long as it's only a little over and for a short time. If I go above 10 mmol/L at any point after a meal I don't eat that meal again. It's probably not very harmful in a healthy person to hit that level on occasion but as it takes me much longer to come back down from that level that it does for a healthy person I suspect that it's not a healthy thing for me to do regularly.

Bear in mind that CGMs can be a little bit inaccurate on the peaks of the spikes. I find the Libre 2s pretty much always overshoot when blood glucose levels are changing rapidly - the true height of the peak may be lower that it appears on the graph. Whenever I use a new sensor I do quite a few finger-prick tests when levels are flat before eating to see how well the CGM is calibrated, and sometimes I'll do a few tests at around 1 hour after eating a meal that has more carbs than my average to gauge how closely the spike on the graph matches the finger-prick reading. It's a pain but I use those graphs to plan my eating for months at a time so I feel it's worth the effort to try to figure out how high my BG levels get after any 'borderline' meal I intend to eat quite regularly.

 

[Calderbloke]

These findings suggest that glucose levels in persons without diabetes frequently reach IGT range concentrations and that a considerable proportion reach diabetic levels

Many thanks for that detailed explanation @HairySmurf ! Based on that I will leave my settings at those values and see how I get on. The overall impression is that "everyone is different" and that CGMs are good but not to be taken solely at face value. Although "no finger-pricking is allegedly needed" I'll continue to do this: always useful to have these figures. Fortunately the LibreView app seems to allow retrospective range changes that will alter the displayed graphs.

I'm due to start my NHS Diabetes Prevention course soon and will be discussing my results so far with them: hopefully over time I'll getter a clearer picture of what's happening and ultimately my A1c will improve!