PGS measure : does anyone use it?

Greetings all,
As i build my understanding around monitoring my glycemic control, i came across the PGS measure, which purports to summarize a lot of information around control in a single number (developed by Dexcom i beleive). I think it aims to multiply %age time-out-of-range by average BG by the GVI (length of the line), and hence incorporate both the volatility and the mean level into the result. It is helpfully calculated by xDrip+, allowing daily monitoring as well as 30, 60 and 90d averages, without downloading data and messing around in Excel.

It sounds intuitively clever, but i can’t find much background information on it, particularly what sort of levels we should be looking to target. All i found was:

  • an article by Bionicwookiee, suggesting 0-35 = non-diabetic ; 35-100 = okay ; 100-150 = poor ; 150+ = very poor. Obviouly it depends on your chose range, but 35-100 is extremely wide… most of the days i would consider pretty horiffic come in at under 100.

  • the only scholarly article i found was, which makes reference a similar PGS score, but with an additional factor of the number of hypos/hypers and their severity… which sounds an improvement, but is not the one reported by xDrip, so the recommended levels aren’t comparable.

  • I see some discussion on FUD here: XDrip+ Now Displays GVI and PGS, but not much else other than that.

Given HbA1C is so limited (given its ignorance of variablity and latency of measure) i am keen to find a theoretically robust alternative that is easily monitored, without the need for bespoke date manipulation. PGS would seem to tick the boxes, but the suggested ranges just don’t seem tight enough to make it be of much practical use.

Does anyone else monitor it? And if so, what levels do you target, for what BG ranges? Or does anyone follow any other ‘catch-all’ metric that is easily monitored?

Many thanks, as always.


We don’t use PGS, and since the ranges you have outlined are really large, it wouldn’t seem to work for us in helping motivate us to keep getting better. We currently just use Time In Range (TIR) + HBA1C. That gives us two things that can be monitored easily to keep trying to get better in. If it isn’t obvious, TIR is what we monitor every week or two to try and judge how things are going as we work towards our A1c measurement every 3 or 6 months. But I am sure there are those among us that are being more sophisticated about it.


I follow both GVI and PGS as calculated in xDrip+ and Nightscout. They are always in the excellent range, so I don’t put a lot of focus on them. I prefer to focus on TiR (Time in Range) and SD (Standard Deviation). My ophthalmologist also emphasizes SD as well, over hbA1c. He said the big swings is what does the damage. Both TiR. and SD are also provided in xDrip+ and Nightscout as well as in Tidepool. These two measures are much more difficult for me to maintain an excellent range. My goal for TiR (60-140 mg/Dl = 3.3 - 7.8 mmol/L) is 90%+, and SD goal of 15% or lower. I’m managing to hit my TiR, but SD is 19% 1-3 months :frowning:

I also keep an eye on the Time in Fluctuation as shown in the Nightscout report in the bionicwookie link you included in your post. I don’t know what the ideal range is for this but I assume the lower the better!
For me, it is difficult to achieve such low values, as shown in the link!


Thanks, @Trying. 15% of what? mean BG? in which case, i guess that’s the (preferred) ‘Relative SD’, or ‘CV’ measure. In which case, that’s 19% is very impressive, and 15% is incredible. I am nowhere near, and since (as discussed at length) i find i am nearly always moving up or down (i eat a lot, and i am active, so i find myself continually tinkering), my 90d CV is 35%. Pretty terrible. I just can’t seem to get it down. Same for TiR, to be honest… i am at 70% (3.5-8mmol). This is improved in the last couple of months (since CGM, Levemir, 0.5 unit doses etc) but still light years away from your sort of control.


It is the Standard Deviation, which is calculated on the Average BG. My CV (Coefficient of Variance) is usually slightly higher than my SD, maybe by 1 or 2% higher. Experts recommend that CV be 36% or less, so you are within the recommendation :slight_smile: .

Both CV and SD are provided by Tidepool. I’ve read that healthy, non diabetics have an SD of 15% or lower. That is why I target that number! I can do it some days!

Well, I know you are very active, and in my experience, exercise adds a lot more complication to managing BGs. Of course, its benefits greatly out weigh the extra work in managing D, and of course, exercise does increase insulin sensitivity. I continue to struggle w/ exercise myself. I’m a runner, and although I’ve made HUGE strides w/ the help of FUD (Eric, DaisyMae, and many others), I continue to have bad days where I will have a low, then followed by a high. Happened today. I managed to complete my run completely within TiR (started at 114 mg/dL = 63 mmol/L and finished at 93 mg/dL = 5.1 mmol/L). The run was under 2 hours, with 21g carb and 0.4U bolus. So that worked out beautifully. Unfortunately, I started spiking right away post run, so I accepted the .45U bolus (calculated by Loop/pump for the lack of basal over previous run). Still going up after 10 minutes, so I took another 0.5U bolus. That was a mistake! I ended up going low. I so often sabotage myself!! I do this time and time again, and I beret myself for it, then do it again!

I know you are MDI. I switched to a pump primarily for running. I wanted to be able to control my basal more, plus easily give small boluses during exercise. I know you’ve asked whether it is worth the extra effort, but I actually find it to be less effort using a pump, and I can fine tune my injections more easily. When I was on MDI (prior to joining FUD), I wanted to take small injections, less than 1U, but found using the eyeball method with the 30ml syringe difficult for < 1U injections. I have to say though, you are doing really great being on MDI with all of your daily exercise!