Basal vs Bolus - lessons learned

It's so easy to get into a rut or develop (and continue!) bad habits. I hope this generates some discussion of the basal/bolus breakdown.

I always quote the rule "get your basal right, then go on to your I:C and ISF" but I haven't thought much about what it means. Numbers are tricky; insulin is trickier. (good saying). You can set your basal to high and have it doing the work of bolus and it still works out-sort of...but is it a bad thing? And the formulas of percentage just don't always hold true (due to varied carb intake, etc)

So since I started insulin (5 years) and my pump (3 years) I've found I do a lot more tweaking of basal than I:C; but other people seem to say the same thing. I always say "I don't bother with basal testing, I just tweak basal rates according to results - 2 hours ahead of the "problem". I think I may need to eat those words.

Last Friday I had a medical procedure for which I needed to fast after breakfast on Thursday. Most people had to fast all of Thursday but they said I could eat breakfast since I was "a diabetic". I didn't bother to tell them that my pump keeps my BG steady even if I don't have food, because I like More words I may need to eat. I went to bed at some reasonable number (110 I believe) and woke up at 40! Huh??

Backtrack: I've been waking up high consistently for awhile now and have slowly been tweaking my basals to fix this. The numbers are less severe, but still a ways to go. I repeat..."40?? Huh?" Followed by: "Hmmmmm..."

When I got back home I took some time and studied my log book. (3 weeks on a page). I had a few highs at my 2 hour dinner pp but not many. I had a few highs at bedtime, which I corrected. So based on that info I had concluded it was not the I:C but the overnight basal. I studied it further and noticed: I fell asleep without doing my bedtime test a lot. The days I was very high in the AM, I had had medium high carb but high fat meals. Hmmm. I added one carb to my dinner I:C and also made my ISF so my corrections had a bit more insulin. I reduced my overnight basals a tad anticipating that had never been the problem. Bang! I woke up at 33! Yikes! More reduction of the basals and I think I'm on the right track. I think I've definitely been off it for awhile!

I think basal rates have a large influence on BG control. We tend to discount their effect since the numbers per hour are small compared to the usual meal or correction dose. I understand that the level of continuous flow that makes up the basal rate controls the release of glucose from the liver.

I've noticed that even a 0.1 unit/hour increase has a dramatic effect on BGs. I've been challenged by overnight (1:00 a.m. to 6:00 a.m.) BGs rising to about 160 and then coming down to about 120 @ 8:00 a.m. 160 is not that high but I'd prefer to keep my BGs under 140. I've found that I've had to increase my 12:00 a.m. rate from 0.4 to 0.6, the 1:00 a.m. rate form 0.6 to 0.9, and the 4:00 a.m. to 6:00 a.m. rate from 1.2 to 1.7. I made these changes in 0.1 unit increments. The early changes seemed to have little effect and then the last 0.1 step moved the BGs a lot. It was not a linear effect.

This whole process has taken the better part of two weeks. I've been through this before. What usually happens is I get very good control for a while and then I'm forced to roll back those changes.

During this time I've adopted a technique that AR has mentioned here. When I see a post-meal BG line (I use a CGM) that is slowly marching upward and my experience has shown that it will not stop until I hit around 200, I start a +200% temp basal rate. I've found that it effectively slows then stops that increase and gently returns the BG to the normal range. I cancel the temp basal +200% when my BG is around 120. This is strange for me since I've tried to change the I:C meal ratio as well as taking a correction dose and those tactics do not alter the upward marching BG line. There's something magic (something I can't explain) about the basal rate.

I'm amazed that after 30 years at this game, I'm still learning the art of BG control. I now know that my basal rates do need to be changed from time to time. Basal rate management is definitely not a "fix it and forget it" scenario.

I think you've made the correct conclusion about your basal rates being too high in the evening and overnight. Your medical test fasting exposed that. Your basal rates must have been doing some of the bolus work. That's the power of the basal rate test. It isolates the liver glucose from the meal glucose.

Thanks, Terry, very informative to hear others' experiences. I don't think I will stop tweaking my basals, I just need to remember it isn't the only tool in my tool box. I too have experienced the "little effect, little effect,!". I too notice that everything comes into line after some tweaking and things are very stable for a few weeks or a couple months and then it's tweak time again.

I don't really understand the temporary basal rate people talk about using for an immediate problem with a high. I know the rule of "two hours later" is an algorhythm as some takes effect right away, but it still seems too delayed to really work. I definitely don't understand this concept as people apply it to exercise for the same reasons (but then I don't understand exercise itself as a

Yep, I was just avoiding having to fast until I was forced into it!

My endo is really pushing me to a 50/50 basal/bolus split. I tend to be higher basal 70/30, for example. I reduced basal from 7am to 5pm by .01 last Friday and things seem OK. She says that diabetics on a pump do better with a 50/50 basal/bolus split. So maybe my basal is too tight and my bolus should pick up the slack?

I do have a question--those of you who set a temp basal at 200%, what pump are you using? I have played and played with my Medtronic and it only allows me to set the insulin per hour. So for 200%, do you just double the dose? Or am I missing some technological wonder of my pump?

I use the Animas Ping pump. Its temp basal feature is calibrated in % of the permanent basal rate. It allows adjustment from -100% (turns basal off) to +200% (2x).

I guess with the Medtronic you just need to do the arithmetic and set a basal rate of twice (for +200%) the usual to get the same effect.

BTW, my basal/bolus split varies from 45%/55% to 55%/45%. I don't always eat the same meals and sometimes I will skip a meal. I would disagree with your doctor, if s/he wants you at a hard and fast 50%/50%. We are not textbooks.

Your 70%/30% basal/bolus split does seem a bit off to me. Have you done any basal testing to verify that? In the end, if you're taking the right amount of insulin at about the right time, it doesn't matter about the split. But if you're forced to fast, like Zoe recently did, then you can get into trouble.


I have the same Endo issue. I'm T2, so that 40 basal / 60 bolus split is never going to happen, due to the fact that no one can prove what my pancreas is actually doing... You have to do what gets your numbers in your range.

On my Medtronic Pump, 200% is the highest temp basal. If I need more than that, I will do a Square Bolus. (Take the additional units per hour, multiplied by the number of hours, and set it.) The 200% cap is a safety feature.

What pump are you using Spock? Here is the way to set a % rate - from the user guide of the Revel:

Delivering a temp basal
A temp basal cannot exceed your programmed Max basal rate.
1 Go to the BASAL MENU. Main > Basal
2 Select Set/Edit Temp Basal, then press ACT.
3 The SET DURATION screen appears. The duration will flash. Duration is the amount of time it will takefor the pump to deliver the temporary basal. Enter the desired minutes or hours (30 minutes to 24 hours), then press ACT.
4 If you have selected insulin rate as your temp basal type, the SET TEMP BASAL U/H screen appears. If you have selected percent of basal as your temp basal type, the SET TEMP BASAL % screen appears. The temporary basal rate will flash. Enter your temp basal rate, then press ACT.
5 The BASAL MENU screen appears with an open circle at the top of the
screen. Your pump is in Special mode; temp basal is now set and delivering. Exit the menus.

My experience is I fluctuate from day to day and there is no way to really calculate anything for sure for me. I have tried reducing my basal to help lows and then I just spike too much for my comfort at times and I still have lows anyway, actually I spike anyway even with more basal, but less probably , so adjusting it didn't help at all.

I think if you're on mdi you have no way of really adjusting basal in any significant way that will actually help, if you tend to fluctuate a lot, once it's in you that is it. I do plan to try to get a permanent pen with half units or smaller to try and adjust my doses more, syringes don't work for me as I can't really tell what I'm dosing with all those confusing lines which are so tiny. So when people come on here and say all you need to do is have the right doses, basal, rates, etc. I think, no, that doesn't work for me at all because I fluctuate too much and I often can't tell when or why it may happen, other than my general pattern that often I spike 2-3 hours before my next basal shot is needed. I often will go low when my basal kicks in if I correct for any spike then also. Sometimes the basal seems to start to act immediately in me and sometimes it takes 1-2 hours.

true, that...meeeeee! so maddening!

Are you considering a pump, meee? I do believe that we all vary in how stable we are with our BG - something I call "the luck of the draw" but pumps definitely make life more predictable!

I'd been frustrated with my basals for a while. .8 was too much and .775 wasn't enough so, like Goldilocks, I figured I'd try "just right" and went through and programmed 1/2 hour intervals of .8 and .775U to "fake" a .7875U/ hour (I guess it's real rather than fake...) and it's worked great! I've always liked "hot" basals, 60ish% but, when I nudge them down, it seems to really smooth things out. I should look at it again sometime but have been busy at work, bringing work home, just taking a break to post.. :-(

Sorry my IPad won’t let me reply to Spock so am replying to thread…

Spock, you must have your temp basal set to units not percent. It’s been a long time since I was on a Medtronic but there’s a separate menu under the basal section where you chose the type of temp basal. It’s separate from actually setting a temp basal.

Hi Spock,

You have to first choose your basal type. In % or units. go to basal/ basal setup and scroll down to temp basal type. Now you will be able to follow Karen's instructions to choose a % for your basal. Personally I'm used to using the units for exercising but I'm going to try to change over to %. For the moment, I've decided to fast and reset all my basals. I've been off for a while. I'm going through my books like I've never read them ! It's amazing how everything can be fine for weeks/ months then all of sudden all is off. What is the culprit??

WHOOOEEEE! Thanks Man_in_France! I use a Minimed Paradigm, this is my second one---never ever knew I could do that! Thanks to all!

I'm still a relative newbie, but if my basals aren't covering just the basal, it makes me eat more because I've got to compensate for the excess insulin with food. Having an empty stomach no longer is an option. Additionally, there are more overnight issues (highs and lows) for me. But it's hard to get that sweet spot with the basal, and it seems ever changing (winter, summer, exercise, being sick, etc). Also eating habits are pretty critical. If I'm eating a lot of late night food, things get out of whack.

>>>>>...She says that diabetics on a pump do better with a 50/50 basal/bolus split. So maybe my basal is too tight and my bolus should pick up the slack?

The 50/50 split is a "rule of thumb" only and I would be wary of anyone suggesting changing basal rates to try to make them fit to an arbitrary rule, For a start total daily bolus dose is going to be totally dependent on your carb consumption, so a dedicated ultra-low carber (Dr Bernstein's brother-in-law) is going to have a higher basal:bolus ratio compared to an endurance athlete (6000 cals of carbs per day whilst trekking overland to the South Pole).

My basal/bolus split is the other way, typically less that 40% basal. My endo once suggested that I must be covering my basal with excess bolus , so I showed him my CGM readouts.


Quite a bit of detective work :-) I often go to bed at some reasonable number 4 hours after eating a high fat (but not unusually high carb for me) meal and wake up two three hours later 160-200. In theory, bumping up basal at bedtime to cover the late hitting carbs is the wrong approach but what is the alternative other than avoiding those meals. I always snack up to 95-110 at bedtime so that if my bolus is higher and I arrive at bedtime lower - all I do is snack and then the carbs hit.

For all we like to think that pumps give us the ability to adjust our diets on the fly, I think the reality for most of us is that we can come up with something that works with a fairly narrowly defined eating pattern but if we really shift, there's potential hell to pay.

I know the "standard" advise for Jewish pumpers who want to fast on Yom Kippur is to cut basal by about 50%. That makes more sense to me now after your story.

Take care


PS - How do you fit 3 weeks of data on a single page? You must write really, really small :-)

I agree that some meals are just problematic. Combo boluses are complicated and I think the formula would vary by food. It's almost like you need to do "bolus testing" to see when the carbs hit and what combination of bolus,(extra over the normal I:C suggestion), duration and split works best for each food. Actually, responding to this question makes me think I should just start keeping records on trial and error with the usual meals that give me problems. There aren't that many and some aren't extremely high carb, just medium carb and high fat, like quesadillas which I make at around 28-32 carbs.

There are enough lines in a wide ruled small notebook to put the amount of days and I just draw lines for waking, breakfast, lunch, dinner and bedtime. The actual foods go on separate pages and I footnote corrections to a correction page. It works for me. I yellow highlight highs and blue highlight lows and at the end of the page I have enough data to see if there are any patterns to act on.

I don't think I will ever feel safe with a pump even if I could tolerate having what is essentially an iv line in me all the time unfortunately. But of course if I get totally out of control with constant high bg I would have to think about it maybe. I hope something better comes along soon so I can get more stable, steady control maybe though.

Zoe, I'm super sensitive to anything in me like that and I have so many allergies irritations etc. The cgm was very painful and it was very inaccurate and I was so wanting it to work for me too.

Most people's hesitation prior to getting a pump is the "something in or attached to me all the time" thing, which ends up being a non-issue pretty quickly. But with your sensitivity meee, that might be a deal breaker for you. One option that you might try would be the metal sets which Jen and others who have allergy issues report work for them.

I feel safe with my pump because I'm the one that programmed it (and continues to do so). I couldn't imagine having a doctor program it and not understanding what the numbers were about - that would definitely make me feel unsafe!