Eating Basal vs Fasting Basal

In case this helps anyone else I’m posting this here. YDMV.

[Background: My basal rates have all been set during careful fasting tests. And confirmed with multiple fasting tests.
I am moderate to high carb. On more cantankerous days, I’ll go lower carb to try to wrestle some control out of the day.]

I have started using an extra 10% basal during “eating hours” to dampen post meal spikes and support my body’s evidently different insulin needs in an eating state vs a fasting state.

I remove the extra basal about an hour before bed when I’m going into a fasting state.

If I use my fasting basal rates all day long, my meal boluses never work out. I go high and stay. Or I tank early and feed the drop. It’s just terribly mismatched no matter what I try.

If I use my extra basal (that’s needed during eating hours) overnight during fasting, I inevitably tank.

So far this is helping me out quite a bit. And this is of course it’s own thing separate from varying levels of insulin sensitivity depending on what my hormones are doing on that given day.



I think the idea of doing fasting to set your basal is wrong. Because…you are normally not fasting.

When someone does that, they are finding the perfect basal rates for a fasting state. Great. That will work well when they are fasting. And then will confuse them when they are not fasting.

A fasting state is not like a fed state. It would be like learning to fly in only a simulator and never actually getting in a plane. It just isn’t the same thing.

I know the general belief in D Land and by the endos in D Land is that basal has nothing to do with eating. And people who write books about it tell you to do fasting basal tests.

But they are just plain wrong. Or in reference to my flight simulator analogy, they are plane wrong.

Your basal rates have a lot to do with how much you are eating. You cannot separate basal from food consumption.

I am glad you are making this connection. Here is a post about it that is somewhat similar to what you are finding.

Basal rates related to food consumption


Hmmm. I evidently not only read that post, clicked “like” on it, but I also commented!

I’m going to shoot for more than five hours of sleep tonight and see what that does for my memory.

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I knew you were drunk when you said this :arrow_down:


It was early in the relationship! Way too optimistic on my part. Which rarely happens…


I do the same for dinner, which can easily extend, unpredictably, over two to four hours, with breaks in between courses, so an increased basal copes with the food much better than intermittent boluses on their own do, with their resulting spikes or crashes. This is a permanently programmed basal, not a temp, so it would be a problem if I missed dinner, but I never do.

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i am just going to reaffirm what Eric has said. my “fasting” basal rates are completely inadequate for my real life. they only represent the part of me that is not eating or moving about my home (or while sleeping), watching tv, etc. they provide little to no benefitial information.

I know that if i want to nosh during the day, that if i set my basal rates a little higher around that time of day, i can include some cheese or other snacks without having to bolus. which, IMHO is a major benefit.

in any case, Eric is the responsible party for helping me get my own basal rates adjusted to my “real” life needs. NOT Steven Ponder or whatever that other guy’s name is. Basal testing is, to me, necessary, but i have found that it is much easier to start with approximations and to look for patterns at different points of the day, and then adjust accordingly until you’ve honed in on a working profile.


On shots, I would base my Lantus dose on whatever lead to the best control during the day (eating hours)…but I would tank overnight every night. The dose that lead to no lows (or fewer lows) overnight would result in a stuck 200-300 all day despite rage injections. Correlation?


maybe Lantus isnt the right basal insulin for you? have you tried any others before?

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Lantus is the only long acting shot I’ve tried. I’ve thought about Levemir but haven’t tried it since podding.

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Prefacing this with - I’ve never done a fasting basal test (and my memory is currently shot so I probably posted in the other thread as well, but I’m too lazy to check atm :wink:).

As someone on MDI (Levemir), I know my basal needs to be upped when I have steeper spikes from food. It’s a delicate balance of enough to blunt my food spikes but not so much that I go low at night (I generally sit in the 80-100 range at night - I do eat a snack before bed).


Were you splitting your dose? Initially I had that problem with one-dose Lantus but then switched to two shots a day, with lower dose at night. Kept me happy for a good decade before I returned to pumping.


I never did split the dose. My endo was so hands off and I was afraid to be what felt adventurous at the time.

Did you evenly split the dose?

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Take a look at your pump basal rates and use a Lantus split that corresponds to daytime/nighttime differences in the basal rates you see on your pump.

For example, if on your pump you are doing 0.50 units per hour during the day and 0.75 units per hour at night, that would be a split of the Lantus of 40% during the day and 60% at night.

But if you are going to split basal doses, you might want to look at Levemir as an option. It might have a better duration for you, depending on how much you are taking and what your split looks like.


I can’t remember exactly, but I think the evening dose was fractionally lower – 22 for day and 20 for night rings a bell. Just do what @Eric says and you’ll be cured fine. :grin:


I echo the thought that fasting and non fasted basal is way different… I found that out personally several times.

I split dose Levemir basal and am very pleased with how well it works.


@Eric I wish I could :heart: this sentiment more. If your basal rate was completely independent of eating, then people would have no ability to adjust to starvation. But, as a species used to frequent periods without food, we’re quite good at ramping our metabolic rate up and down depending on food availability. Beyond this – what exactly is our metabolism doing if not digesting food and turning it into energy? Take out the food, and the process has to change.

We’ve done so much basal testing for Samson and I can say 100% that his basal rates in the fasting state will send him high on the 353 other days of the year when he does eat something. To maintain semantic purity between basal and bolus, I do things like log carbs with 8 (or even 10!!) hour absorption, but it seems kind of ridiculous when just having slightly higher set basal rates seems to be more intuitive.

In general, with closed loops I don’t really think the distinction between basal and bolus makes much sense and I think you probably just need one parameter that varies based on lots of inputs (ISF or some such would probably work fine.) That’s one weakness of Loop, IMO.


I’m curious how much the metabolism adjusts for a brief period without food – say, a skipped lunch – compared with longer periods when I’d expect a change to happen – say, being sick and not being able to eat for several days, or being starved as a POW. Would the body even recognize a skipped lunch as a problem? I have a fasting blood test this morning, and now I’m wondering if I should have a different basal rate …

@Beacher I’m not sure but I’m guessing it happens more quickly the smaller you are. When Samson was little, any kind of basal test was pointless because his basal rate dropped by 6 hours without eating during the day. Now I am seeing it’s more like 10– that’s what I’ve noticed on days when, for whatever reason, he vetoes a given meal or we eat a late breakfast or whatever.

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i can only speak for myself here, but if i skip a meal, my BG drops. my body expects food throughout the day. i can avoid this problem with a little snacking, but on the whole, i need to eat 3 meals a day at relatively the same time of day.