Question: honeymoon period and calculating insulin to carb ratio

My sister was recently diagnosed with T1D (it’s been a little less than a month) and we are trying to determine what her carb ratio is. We just got CGM last week or so and what we’re seeing is a lot of spikes right after a meal if it’s not followed by some kind of exercise immediately. And when she does move after eating, she goes all the way down to a low before the next meal or close to the next meal.

She is taking tresiba as basal in the mornings and taking 1-2 units at the moment, which I assume is because of the honeymoon period. When she was first diagnosed it was 6 I believe. Her fast acting insulin is Fiasp and she takes more or less 4 units before every meal (I think because that is what the doctor told us in the beginning?).

Since her basal is so low, would we still use the same formulas (500/total daily units, etc) to calculate her insulin to carb ratio? We think currently her ratio is around 11.5 but since there is so many spikes and lows she is struggling to keep it steady especially after a meal. We are a bit afraid to bolus too much as well because of the possibility of a low before the next meal. It’s tricky to adjust basal since there is not much to change within 1-2 units.

Would love to hear about your own experiences with honeymoon period and what worked. Thank you!

In Response said:

The highs and lows you describe may be more down to timing than the dose.
If your sister's levels return to the required level within 4 hours, a spike will be due to pre-bolusibg too late.
With regard to lows after exercise, she may need to reduce her insulin if she plans to exercise. Common advice is to avoid insulin on board (currently acting fast acting insulin) when exercising
However, I find Fiasp more challenging than other insulins I have tried. I find the speed at which it works is very dependent on my blood sugar level and need to time my bolus accordingly.
For example, it works faster than my digestion if my levels are in the 4s. But can take nearly an hour to take effect if I am in double figures
Bear in mind the ratio you mentioned is only a guideline l. Many find their ratio can get different at different times of the day
And, there is little point in "perfecting" the bolus of basal is wrong. So the advice is to start with a basal test
I notice you mentioned whole numbers. Is this because your sister is unable to do half units? I recommend reusable half unit insulin pens.

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The exercise I mentioned is more like walking after a meal, ex. going to a grocery store. The doctor said to take Fiasp right before eating (2~3 minutes), but I am finding out that is generally not most people's experience.. Thank you for your insight! I'll mention different types of fast-acting insulin to her.