Dear Dani, Grace and Jude,
Note: This page is advice for Grace, Jude and John. For any other reader, it’s information only. No therapeutic relationship is formed – read this.
How do you calculate a fast-acting insulin correction dose to bring glucose back into target?
To do this, three things are needed:
- Target glucose level to correct down to. 5.5mmol/L (100mg/dL) is a good place to start.
- A correction factor. This tells you how much 1 unit of fast-acting insulin drops the glucose by in mmol/L (mg/dL). For example, 1u:3.0 (1u:54mg/dL)
- Current glucose level.
Your diabetes team will give you a correction factor for the different times of the day. The same principle of insulin sensitivity based on fitness and time of day we discussed for carb ratios apply.
Mine are currently:
Breakfast: 1u:3.0 (1u:54)
Lunch: 1u:4.0 (1u:72)
Evening meal: 1u:3.5 (1u:63)
Let’s say my glucose level is 11.0mmol/L (200mg/dL) and I want to correct it down to target. The formula:
(Current glucose level – target glucose level) / correction factor = Fast-acting correction insulin units
Let’s do the Breakfast example.
Breakfast mmol/L: (11.0 – 5.5) / 3.0 = 1.8 units
Breakfast mg/dL (200 – 100) / 54 = 1.8 units
This graphic shows how long it would take to get down to 5.5mmol/L (100mg/dL) using 1.8 units of fast-acting insulin calculated.
Three hours to get into target (less than 10.0mmol/L or 180mg/dL) and four hours to get to 5.5mmol/L (100mg/dL)
What do you think I would be tempted to do an hour and a half after correcting when the glucose had not budged from 11.0mmol/L (200mg/dL)?
That’s right, whack in another correction of 1.8 units.
What will happen then?
The insulin will pile up and send my glucose level plummeting down about two hours later. What is known as “stacking insulin”.
The only way to avert a hypo disaster is to smash in a lot more carbs and overshoot. This is what’s known as the glucose rollercoaster!
It’s not a fun ride.
In fact, that’s exactly what I did on Christmas day 2018, but more on that when we get to Dynamic Glucose Management.
Dani, you are probably thinking there must be a better way to drop the glucose between meals. A strategy that works quicker than the ironically named fast-acting insulin. Ideally, something that works in half an hour, not four hours!
Indeed there is.
Next step? Activity and Exercise
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