Fasting For A Basal Adjustment


I have been doing mini fasts to test my basal rate at different parts of the day. I would love to do a full day fast, however I have not been able to make it that far without giving in and eating a meal.

Today I saw my endocrinologist and asked if I could eat no carb meal while fasting. She said absolutely not because then it wouldn't be a fast. I know it wouldn't be a "fast" but in theory is that a pliable way to see if my basal rates are well adjusted?

So my question is: if I eat absolutely no carbs in a day can I see where the basal rate is spiking?

If not, how do you fast?

Personally, I have never bothered with the fasting tests. I just keep diligent records and test 10 times a day. Then I look for patterns of highs or lows at similar times, say on waking, bedtime or before my meals. Then I tweak the basal by the smallest amount my pump allows for the time period where I see a problem and see how it affects things. It works quite well.

Mini-fasts are the usual way to basal test. The reason you can't eat other foods while basal testing is that protein and fat are also converted to glucose although more slowly and at lower percentages. You might not have to count protein and fat to dose accurately but you do need some insulin to cover them which wrecks the basal test.


I agree w/ Zoe in that I don’t fast. Before meals= basal “controlled” and after = bolus and that seems to work? I’ll adjust a setting, try it for a couple of days and, if it works, great! If not, well keep yutzing aroud is better than fasting.

Don't do it as often as I should, but I've only used the one meal at a time fasting method. One day I don't eat breakfast, the next I skip lunch & then I fast for dinner. I do it three days in a row so things will be consistent regarding patterns. Also because I want to get it over with. I've easily seen where the spikes & lows are. It's the only way I've found to know what's really going on & no big deal for me to miss a meal occasionally. Any changes I make are small ones & I test a lot the days following adjustments.

Maurie is right. Around 58% of protein converts to glucose, as does a small amount of fats. You can't tell anything if you're eating.

I've done a few of the mini-fasts as well. I did read that it was okay (I cannot recall exactly where - but I am sure I'm not making that one up) to have a few nuts or bits of cheese during these fasts if needed. The key is just to have a few nibbles to quiet the appetite, etc. Definitely not a full no-carb meal though, for the reasons Maurie mentioned.

I certainly do not enjoy fasting - and I'm sure my coworkers are thankful I don't do it often - so I do tend toward futzing around with basals and I/C ratios on the fly most of the time.

I actually don't believe that all-day fasts are useful. After a certain point, it is just an unnatural condition and my body reacts badly. I do mini-fasts. And even with mini-fasts, I can't really do it all, for instance mornings. If I fast in the morning, my blood sugars go south, they just rise and rise, hardly my natural pattern.

The point of your basal is to keep your fasting blood sugars between meals right on target, not to provide the level of insulin you would need if you fast all day.

And if you are going to fast, you need to really fast. Just small amounts of water. Eating anything can disturb your blood sugar. Certainly no protein, I have to bolus for protein. I count 50% of the grams of protein as carbs. And if you eat a volume of anything, even water and ice, it can induce an effect on your blood sugar (the "Chinese Restaurant Effect").

I've never been able to do that. I do "mini-fasts" where I fast throughout the basal period that I want to test, but that's it. There's no way I could go a whole day without eating and I really don't see the need to try. It seems so artificial to me too because it doesn't really replicate what you actually do. If I'm fasting, I won't be exercising or doing anything else like I usually do (because I probably won't have the energy), and this (IMO) negates the point of testing.