Basal Test Guidelines

Something’s bugged me for awhile and I was wondering if any of you could help. The basal test guidelines seem to preclude the possibility of your Basal being too high. Why’s that?

You must have ate no less than six hours ago. You must have also had zero readings below 4.0 in that time.

However if you took the optimal amount of Bolus for the last meal and your Basal were too high it is highly likely that you would see your Blood Sugar going low before the end of that six hour window. As after your Bolus controlled the carb spike, your Blood Sugar would keep dropping regardless. As such, to meet the preconditions of starting the test it is demanding your Basal must not be too high to start with, because if it were too high you would not have met the conditions for starting the test.

Am I missing something or misunderstanding something?

EllieM said:

An interesting point, can you give me a link to the basal test guidelines you are using? Am guessing that if you go below 4 overnight you'll probably reduce your basal anyway?

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These ones, primarily because they are the most clearly written, but you see this guidance in other guidelines to.

https://www.mysugr.com/en/blog/basal-rate-testing/

Juicyj said:

Hi @StewM The whole idea about starting a basal fasting test with levels below 10mmol/l is to ensure you're starting on a level playing field and ideally when you have a flat stable line, if you're above this when you start and it's been over 4 hours since your last bolus/correction then you will need to correct this to ensure you're not going to continue northwards so will have to abandon the test, it's more of a safety net starting in range. I tend to break basal fasting tests down into one session at a time, so will test a morning slot a couple of times before making any assumptions about changing my basal rate. I also try to eat a low fat/lowcarb meal prior to a test to ensure I take minimal bolus therefore limiting the room for either hypo or hyper affecting the test period, I tend to think of fasting tests as hard work in themselves as even getting levels in the 'range' to perform the test can be a test in itself..

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I’m not sure I’ve made my point clear so I’m going to give it in a little more detail.

Following the two guidelines I’ve quoted above.

You take a meal, wait six hours, if you get a low you don’t begin the test.

However let’s make some assumptions.

1) Your Bolus dose is the perfect.
2) Your Basal dose is too high.

In this scenario, you are unlikely to start the test, as if your Bolus has done it’s job correctly, your Basal (being too high) will push you out of range before you could even begin the test. Therefore, the Test itself couldn’t tell you if your Basal Rate was too high because, if it was, you wouldn’t begin the test in the first place.

Juicyj said:

Hi @StewM Yeah I see where you are coming from about being pushed out of range before even starting, but if your basal is in indeed incorrect then it's not necessarily going to push you out of range before even starting the fasting test but instead you will see either a rise/fall relating to the basal action during the fasting test. If you're going out of range before starting the test then it would be your bolus affecting the reading or other factor such as stress/exercise/etc.

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See, I'm not sure I agree with your final sentence. The Basal is always affecting your control. So you can't eliminate it from the range of possibilities that easily. Yes, it certainly could be other factors, and likely for a variety of reasons, but going back to the case I've outlined.

Most foods don't spike your blood sugar for six hours. Obviously, it varies a lot from food to food, but a lot of foods will stop spiking you after three hours. You would want your Bolus to have you in range at the three-hour mark. Yes, your Bolus is likely to still be active, but it's likely to only be very weakly active because of how action curves work. If your Basal is too high, it will always be pushing you low. So as you stop getting the benefit of the Blood Sugar boost from what you ate, that will become more and more of a factor. Whilst yes, the Bolus is still a factor and could be the primary factor, the effect your Basal is having on the equation should not be ignored surely?

Juicyj said:

Hi @StewM I am curious to ask - have you done any basal fasting tests to actually experience this first hand or are you simply making an assumption that this would happen ?

Further to your point above - I should of added that if you had eaten or taken a correction within the 4 hours before the basal test then it would of been the bolus/exercise/stress/etc affecting your starting point because you've either under/over estimated either carbs eaten with bolus insulin taken - a rise/fall with the wrong basal ratio can take much longer to materialise and any rise fall would present a steady trend line upwards/downwards rather than a steep rise/fall and this is what a basal fasting test would pick up on.

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Well, no. Precisely because of the quandary I'm talking about. I can't start a Basal Test when my Blood Sugar has been low in the past six hours. I am experiencing a lot of lows that I believe are being caused by the Basal, but in the absence of a Basal Test, I'm dropping my Bolus instead. However, I always reach a point with the Bolus where my Bolus drops too low and I end up wildly out of range because even a too high Basal isn't going to cover a gap in the provision of Bolus.

So I'm stuck between going high and inevitably having to take a correction to control it (in which case I can't do a Basal Test for a completely different reason). Or I'm staying in range for 3-4 hours but then having a low between hours four and five which stops me even beginning the Basal Test in the first place. I'm highly sensitive to insulin in general, so a single unit of Insulin makes a massive difference.

I think I have ample reason to suspect it's the Basal causing these issues, but going by the Basal guidelines, I shouldn't even start a Test ever.

*edited to correct typo