Overnight Basal Rate Testing

I'm ignoring that outlier (281 mg/dl) - see how it doesn't fit?

Numbers and Lines

I had a hunch that I could use some fine-tuning.  But overnight fasting basal rate testing sucks, so I kept putting it off.  My doc finally convinced me to bite the bullet, and I’m actually very glad I did.

The idea behind basal rate testing is to eliminate as many variables as possible, so that any changes you see in your blood sugar are most likely from your basal rate.

Wait – am I getting ahead of things here?  Do you guys know what “basal” is?

You need insulin all the time.  I mean ALL the time.  Even when you’re not eating, you need a bit of insulin in you.  In a person without diabetes, the pancreas has a way of knowing exactly how much is needed for each minute of the day.  In my case, I need to figure out how much my pump should deliver on an hourly basis.  That hourly insulin is called my “basal” insulin.

In theory, if your basal insulin is set right, you should be able to fast indefinitely and your blood sugar should stay relatively stable (without extra influences like exercise or illness).

In order to test your basal rate, the idea, again, is to eliminate as many variables as possible.  The typical variables include food and bolus insulin (boluses are what you take for highs or when you eat).  There are a million other variables involved, but we’re only worried about the ones we can influence.  Get rid of as many of them as possible, and any changes you see in blood sugar are most likely from that basal insulin.

I woke during the night to test every two hours.  There’s nothing nice about doing that.  And every single time my phone alarm buzzed me, my wife popped upright and asked “what was that?!”  Poor thing is so accustomed to listening to any sort of pump or CGM alert coming from my side of the bed…

So we both had a less-than-great night of sleep, and I felt bad about how it disturbed her.  I thought about the torture that is overnight basal rate testing and how it affected more than just me.  It’s not fair that it should mess up her sleep too.

But look what I found!  Nearly 100 point rise between midnight and 8:00 AM!  I had a hunch, but holy smokes!  To be fair, this was only ONE night of information, and there were a couple things that might have skewed the results.  The only real way to know if it’s a fluke, or reliable data would be to do another overnight test.  Which I will, soon…  but not too soon.

I will probably make some adjustments based on this information, even though it may not be exact (what in diabetes is ever exact?), then recover a while before repeating the test.

Basal rate testing is a pain, but once you get your basal rates really dialed in, rumor has it that things with blood sugar management get a lot better.

Wise words from my friend Dan (who impressively maintains a 5.x A1C by the way…):

If you can own the night, you can also own a majority of the day AND the weekend! Keep at it! It sucks, but it will help!

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19 Comments on "Overnight Basal Rate Testing"

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I’m not on a pump so do I basically check my basal the same way?


Glad you didnt see any darn spiders to mess it all up 🙂 I haven’t basal tested in 4-ev-er! Might as well now when Im up with the kiddo almost every two hours some nights anyway right? I think my basal result will be my next blog post…wish me no spiders or spikes!

thanks for this thread, and the conversation about it. Keeping a consistent blood sugar through the night is important as one sleeps 6-10 hours a night and this is a substantial amount of time to be in your goal BS range to keep a1c down. Not ingesting carbs and covering with insulin at night while sleeping is a great motivator to fine tune basal rates to keep a level BS as there is less variables than wake hours with meals, bolusing and activity. Using a CGM provides me BS information all night and alarms alert me if I go above… Read more »
Brendon Livingstone

Hi Scott

Thanks for the post. As you know my Lantus basal amount has caused me A1c issues in the past, and I now think that I am in a much better place with my current higher Lantus dosage. However, I am basing that view purely on my improved morning blood sugar levels. It would probably be valuable for me to do the overnight basal rate testing to confirm.

Thanks for the heads up

Scott, Thanks for the post. I got an education from your basal insulin description that beats anything I’ve read elsewhere. Describing the ordeal of collecting measurements every two hours made me think of the latest gadgets that Amy Tenderich (DiabetesMine) reviewed from the CES conference on health tech. One that caught my attention was the Ford Motors partnership with Medtronic to link the Guardian RT CGM to sync with Bluetooth so you could read your levels from the dashboard. In addition, they have another prototype of a heart rate monitor that reads data from the car seat (electrodes are built… Read more »