A successful insulin bolus is all about the balance between amount and timing.
Arden recently had Chinese takeout that consisted of sesame chicken, white rice and edamame.
Take a look at her 24 hour Dexcom graph and see if you can guess what time Arden ate the Chinese food. The yellow block represents a restart of her Dexcom CGM.
Now lets talk about the insulin that we used for the meal. Try not to look at the next graph yet...
History tells me that Arden will need between 9 and 10 units of insulin for this food. I don't know how much she'll eat and I don't know how many carbs the food contains. Honestly, I don't care about the carb count for two reasons. 1. I know historically how much insulin this food requires, the trick is to time it correctly. 2. Even if I use the correct amount of insulin the bolus won't work if it's mis-timed.
Example of Correct Amount of Insulin not leading to desired result
Bolusing the entire amount too soon will cause a crash while eating because the carbs will get overpowered by the insulin. Correcting this low will lead to a crazy high later (unless you add insulin, which you'll likely be afraid to do because of the initial low. However, that would likely be the correct thing to do). Outcome: UNDESIRED
Bolusing the entire amount too late will cause a spike that won't come down because the carbs will overpower the insulin, rocketing the BG. This result now voids the "correct" amount of insulin. Yes you used the correct amount of insulin for the food initially but the unintended spike has not been compensated for by insulin. Mis-timing the insulin created another insulin requirement. This spike will last forever without more insulin. Outcome: UNDESIRED
Take away: The insulin, even in the correct proportion, will inevitably not be successful if it is mis-timed.
What does timing mean in simple terms?
The fight between carbs and insulin needs to be balanced. Imagine a tug of war. If one side pulls first, the flag in the middle of the rope becomes uncentered. Now the side that pulled first has a huge advantage that the other side probably can't overcome. When we bolus we want the insulin and the carbs to pull at the same time so that the flag stays right in the middle.
The first step to a balanced pre bolus is understanding the insulin. Man-made insulin does not work immediately and you need to figure out how long it takes to work for you. It may be five, ten, fifteen or more minutes, figure it out. None of this will work without pre bolusing. Trust that.
Once you know how long it takes for your insulin to begin to reduce your BG, consider the food. Something sugary will hit your BG quicker while a heavier less volatile carb like bread may take longer to start pulling up your BG but then last much longer in your system. Each food type will need different timing considerations and hence a different pre bolus.
None of this needs to be perfect because you can always readdress as you go (made easier with the Dexcom CGM and an insulin pump but not undoable with injections).
Understand the roll of basal insulin. Pumpers have a basal rate set that is trying to hold a steady BG during the day. When carbs are added and your insulin needs increase, you aren't just stuck with one weapon (bolus) you can also blanket the carb richer hours with more basal insulin. (Extra basal also does wonders bringing down a spike or stubborn high BG). So don't just use a targeted strike (bolus), carpet bomb too with an increased basal rate. Decreased basal rates are also effective in handling stubborn lows without carbs.
Okay lets take a breath because none of this is nearly as complicated as it seems. Lets go over some basic tenets and then look at the Chinese food graph.
You have to pre-bolus to create a balanced fight between carbs and insulin.
Temporary basal rate increases and decreases are a vital tool.
If your BG is too high. You didn't use enough insulin, you mis-timed it or a combination of both.
If your BG is too low. You used too much insulin, you mis-timed it or a combination of both.
When your BG gets high do not spend time trying to figure out why, just get it down. Figure it out later.
When something goes wrong, its not a mistake to beat yourself up over. It is actionable data, a learning experience that will help you make a better decision next time.
CGM users: Stop the arrow without causing another one. Bump and nudge the graph line. Small adjustments will keep you off the diabetes rollercoaster.
It is far easier to stop a low or falling BG then it is to effect a high and stubborn BG.
Often you get what you expect so expect BGs in the 70 - 110 range and make them your goal. CGM users: Set thresholds that allow you to react before it is too late.
Be bold with insulin.
It's time to look at the graph from the Chinese food. Do you remember when you thought Arden ate? Did you guess around 3 pm? Actually, the spike at 3 pm was one tiny snack with a mis-timed pre-bolus. The take-out was at 7 pm. Check it out.
Simply put. I cranked up Arden's basal about 20 minutes before the food arrived and bolused 3.00. Thats 4.00 units in, 6.00 more needed. The next 1.50 went in when the food began to create space between pre-bolus. I need to stretch the insulin impact because there are two different carbs at work in this example. The sugar on the chicken is going to act fast so the pre-bolus and temp basal needed a head start. The next issue is the white rice which brings a heavy impact that is also long-lasting so we need force and staying power. I held the balance of the insulin until the rice started to make its impact around 7:40 pm. I should have bolused the remaining 3.80 all at once but I played it a bit safe because I knew that we were about to lose the Dexcom data for two hours. Had I sent the entire 3.80 at 7:40 the BG wouldn't have made it to 140. Thats it. We tested half way through the Dexcom restart to be safe and to make sure that Arden didn't need more insulin.
You may be inclined to say that this is too much effort but I contend that the few moments that it took to make these adjustments is a far better world to live in then spending the next five hours bolusing a high number that just won't move. It will take you a few tries to make sense of everything but one day you'll have it and all of this will feel easy. Arden eats what she wants and her A1c has been between 5.6 and 6.2 for four years. Be bold with insulin!
You many also like:
Blog post: Anatomy of a High Carb Breakfast
Podcast: Bold With Insulin
If you want to continue to find out more about how we manage type 1 diabetes please check out my podcast. The Juicebox Podcast is free and available on all podcast apps and online. Subscribe and start listening today!
I am not a doctor and this is not advice. Disclaimer is here.