Basal Testing

I was doing a lunch basal and the first couple of hours were okay. The third hour I rose, and I kept rising for another hour. The days before, my after lunch blood sugars were okay for the most part. So, I corrected and cancelled the test. It always makes me a little anxious when I don’t see perfect bloodsugars within the range that it should be. That would defeat the purpose of doing a basal test, I guess. I will have to try it again some other day.


Diabetes is a moving target. It’s frustrating trying to get your basal adjusted when you must abort the basal test because your BG breaks the limits for the test.

I remember when I was adjusting basals several years ago under the guidance of Gary Scheiner. It took me two weeks and many tries to get one good run for each of the partial day segments. Good luck with your continued efforts!


Yep, you have to cancel testing if you need to eat or have to do a correction., tis the nature of this disease. I remember the frustration back in 1996 when I did that testing, and that was when I was on Velosulin, an insulin with the speed (or lack, thereof), of Regular. It was a buffered version of Regular, for use with pumps.

I’ve never been able to do it honestly, but if you can get a CGM or already have one basal testing isn’t as necessary!

I use the Dexcom Clarity AGP (ambulatory glucose profile) report to make changes to my basal rates. Whenever the 10th and/or 90th percentile lines (the dashed green lines) of my 14-day AGP report cross my lower or upper range limits, I start to think about making pump setting changes including basal rates. Since this report collects 14 days of data and displays it across a single 24-hour day (standard day), I can easily see how to time my changes.

For example, from the chart below, the 90th percentile line is crossing the upper limit of my BG range at about 11:00 p.m. and stays there until about 5:00 a.m. This suggests an increase of my basal rates starting two hours before the crossing time or 9:00 p.m. I’ll then lower that rate at 3:00 a.m.

The 10th percentile line crosses the lower BG threshold at 5:30 p.m. and doesn’t return until 8:00 p.m. I’ll lower my basal rate for the 3:30-6:00 p.m. basal segment in an attempt to raise that 10th percentile line above my lower BG threshold.

I don’t intend for this comment to discourage anyone from using the standard basal testing protocol. There is still value in doing that, especially if you’re using a meter instead of a CGM.

1 Like

Scott, basal testing includes adjusting one’s basals until you get the best bg levels. It has nothing to do with the method of checking one’s bg’s (or by your example, interstitial fluid readings).

Basal adjustments always come before finalizing other parameters such as I:C ratio, and drop ratios. Proper basal settings are the foundation from which all other pump settings are then fine-tuned.

1 Like

Oh absolutely, I just meant I’ve never been able to basal test the way my endo has suggested. With the CGM you can just look back at the night before and adjust based on the graph!

right. how did he want you to do it? Back “in the day” (I actually hate that term. LOL! ) , the way to go about basal testing (for pumpers–not for Lantus, etc) was to skip one meal per day so that you didn’t have to bolus for quite a few hours (given that the tail can be longer than 5 hours). If the same results were obtained a couple of days in a row, that was considered useable data and you either made an adjustment or left things as they were if bg’s were good. ONE day’s data was considered not a good way to begin changing basals. Several days, to see consistency (at least you have a fighting chance to make a better adjustment if several days yield very similar results).

After skipping breakfast and getting those basals correct, move on to skipping lunch for a few days and repeat above paragraph’s methodology. (if you woke up way to high or too low, do not do basal testing. If just a little high at breakfast time (but skipping eating), you can still do basal testing until lunch–just realize that all bgs will be higher than preferable. the key is that they remain near LEVEL.

And so on.

oh, and NEW PUMPERS: always begin pumping with at least 25% less basal than the amount used of Lantus, etc. Probably it’s better to start with even less than that. Then ramp up your basals until correct. There are two reasons for doing that: 1) you won’t have to have “emergency” carbs for a low during basal testing, which will cancel the test, and 2) its safer, esp at night if one doesn’t have a CGM with alarms.