Over the past 6 weeks my control has improved dramatically, with my average BG dropping from around 16 to 10 (with some days under 10). One of the difficulties I still encounter is random rising or dropping of BG levels. A peak in my BG levels around 8am (before I woke up) and a rapid drop around 5pm (long after lunch bolus should have finished) led me to try some basal testing.
Having a CGM, the morning rise was relatively easy to fix; Look for the start of the rise on the CGM graph and lower the basal rate around 2 hours prior to that. After a couple of days of minor adjustments I managed to stop the morning rise.
The afternoon rate was a little more difficult to fix (and I still haven’t managed to get it totally correct). From previous testing I know that my boluses tend to last for around 4 hours. Because I bolus for lunch around 1230 the only active insulin in my system after around 1630 should be my basal. Between around 1700 and 1830 my blood sugar level was dropping from 8 or 9 to 4 – 5. This is far too much for basal alone. To avoid any possibility of my lunchtime food and insulin doses I had to skip these, which led to a very hungry afternoon.
The first day I tried this I noticed that the BG drop actually started much earlier, around 1430. I actually had to stop the test early because I had hit 4.5 by 1700. I reduced my basal rate a little from 1230 with a larger reduction from 1430. With these reductions, the second basal test went much better – I dropped from 8 at 1400 to 5 at 1800, with the majority of the drop coming after 1630. I further tweaked my basal rates as a result of this and most of the drop has now gone. My afternoon rates still need some adjustments, but the decreases in blood sugar are far more manageable; There are only so many days of afternoon fasting that I can put up with in a row!
With my morning and afternoon blood sugars more stable, I have found it far easier to maintain constant sugar levels throughout the day.
One thing I have found very useful to keep in mind when adjusting basal rates is that a ‘healthy’ person tends to have one peak in basal requirements and 1 dip, which implies that if your basal rates have more than one peak or dip then the basal might not be correct and is instead being used to cover other things like a lack of bolus.