I really suck at this, could use some tips

How did things go at your appointment with your endocrinologist? Jane

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I’m fairly new to a pump (Tandem t:slim. I am not on CIQ); have used DexCom cgm for 10+ years. My CDE did all my pump training. I tracked carbs, insulin dosages and post meal BG for weeks prior to starting on the pump. No training on how to adjust I:C, correction factor or basal. I am very sensitive to insulin–CDE had me change 4 of my basal rates in one day and I got a lot of fast BG drops and alarms. Prior to being on a pump, a different CDE had me change one factor, maintain that for a few days, then change again if needed—seems being on a pump requires the same for me. How do you know if the I:C ratio should be changed vs the correction factor? Someone mentioned watching BG readings after a meal—how long after a meal? I’ve been T1D for over 60 years and am looking for ideas on how to level things out without so many fast BG drops and help me to be in range more. (I do count carbs carefully, too) Thanks!

Have you looked at the Tandem online ebook linked below? The book’s second chapter, Customizing Your Insulin Dose Setting, covers the settings you seem to be asking about. Perhaps it might help? (The chapter goes over some of the arithmetic I wave my hands at below.)

A Guide to Successful Pumping

The approach I take to decide which setting to change is to test them separately.

The Correction Factor (CF) is only about correction boluses. It controls how much insulin to deliver to lower your BG by a given amount. Carbs should not be a factor when testing your CF settings.

To sanity check your Correction Factor, enter a correction bolus into your pump when your BG is at a stable elevated level and you haven’t eaten anything.

As the bolus takes effect you should see you BG drop back to your target BG setting. If your BG is not lowered enough, then your CF may be too high. The Correction Factor is just the amount your BG should drop for 1 unit of insulin. So if the CF is too large then the pump assumes less insulin is needed to lower your BG.

Similarly, if the Correction Factor is too low, then your BG will be lowered too much. You may need to consider increasing your CF.

The I:C ratio is about food boluses, not corrections. It specifies how many grams of carb one unit of insulin will cover.

To see how well your I:C ratio setting is working, wait until your Blood Glucose (BG) is steady at approximately your target BG. Then bolus for and eat a known amount of carb.

Your BG should go up, peak, and then come back down to your target BG. If your BG doesn’t return to your target BG but instead stays high, then your I:C may be too high. That is, the I:C setting indicates that 1 unit of insulin will cover more grams of carb than it actually does. So you may want to lower your I:C ratio slightly.

If instead your BG falls below your target BG, then your I:C ratio may be too low. That is, 1 unit of insulin will actually cover more grams of carb than your I:C settings says it will. You would want to think about raising your I:C level.


I find that the lead time to do a meal bolus before a meal varies hugely with the type of insulin I am using at the moment (I switch between them a lot). For me, the numbers are:

  • Novolog, 20 minutes
  • Humalog, 10 minutes
  • Fiasp, first 5 minutes of the meal
  • Lyumjev, as I finish the meal
    And what I’m eating determines whether I use an extended bolus or not. For example, for Fettucini Alfredo, I go 50 now, 50 over an hour. For ice cream, it would be all at once.

Another rule I use us that I make very small changed in my basal, carb ratio, or correction ratio at a time, and only change one of those st a time.

I also have six time slots on my t:slim: midnight, 4 AM, 7 AM, 4 PM, 8 PM, and 10 PM. That has worked well for me over the past 6-7 years.

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Thank you! I will check into that book. I appreciate your response!

I’m using Novolog in my pump. I do pre-bolus and have my timing down for that. I think I have gastroparesis (minor case, apparently)–for me a bolus for my evening meal is the tricky once. Dietitian said I have to experiment to find out what works for me. And yes, what I eat is also a factor for that time of day. I have multiple basals set in my pump and totally agree with you on small changes and only one at a time.

Thanks for your comments!

Sounds like there is a lot of good advice posted here for you Jakewriter1. As someone said it may take a little time to acquire knowledge and experience in fine tuning your pump. I think it was also John_S2 touched on it - managing your carb intake or just as important the type of carbs you are ingesting. I think it was also mentioned about consulting a diabetic dietician to learn as much as possible about carb intake, type and how things like protein and fat affect your BG.

All in all sounds like you are doing the right things and I have no doubt you will get there! I admire that you are inquisitive about finding answers and when you do coupled with your own findings from personal experiences you will be all the better for it!

Best to you, -Steve

This is a perfect example of how each of us is so very different in our treatment plan. There are many here that spend a lot of time fine tuning, detail oriented and driven to be the best. And than there are some who want easy and user friendly.

While I strive for my personal goals, I don’t let those goals control my life. After all these years, I want easy. I want to not have to think about everything, all day long. So for me, I use whatever insulin my insurance company is covering this year. I have two profiles, off day and work day. And each of those profiles has two different basal rates. And for daytime and one for overnight. I do have different carb ratios for meals but otherwise, pretty easy and straightforward. I have come a long way from the 8 different basal rates during a 24 hour span. Took me a long while to realize that with a 2 hour lead time for the change to happen, less was better for me.

And with my TandemIQ, I have the easy I have been hoping for! I love being able to not worry about what not eating for most of the day will do to me. The little pump just does its thing and I go on with my life. Or if I am really working hard during my walks, my little pump just does its thing! I so love easy!

And in a few weeks, I start back up with the clinical trial with the iLet pump. Not sure if I will be assigned the control group side or the tes side, but I have been told if control side, I will get the new pump for the second three months. So either way, I will still get to try it for a longer span of time, instead of just the 6 days last time. And I am hoping this will take another thing for me to think about off my plate. No more counting carbs!!! Heaven!

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