How do I find out how much a unit of Humalog lowers my BS?

I am new to insulin and am having trouble with my humalog. I've not had a low yet but I also have not had much lowering my numbers. For example, last night I took 8U and did not see a reduction in numbers for 3 hours then a drop from 171 to 128. I never got below 110. Now I do admit that my meal was higher carb than I usually eat.
Anyway, I'm trying to figure out how to find out how much Insulin I need to lower my BS/U. Right now I'm afraid to do anything before I eat but then I have the food effecting my BS. Since I'm a T2, I still have some pancreatic function which also effects lowering. I don't want to plummet myself into a Hypo but I'd like to see SOME lowering when I take the drug. I'm also wondering why it might be that I need so much insulin with so little effect.
I'm not sure if this makes much sense, I'm in kind of a hurry right now. I'll be back later in the day to be a bit clearer.

There are two ways to use Humalog, bolusing for a meal and correcting for a high blood sugar. Most people on MDI do carb counting and bolus before their meal. If they are still high 3-5 hours after a meal, they may consider a correction bolus. If you want to figure out how much insulin to inject for a meal, you count the carbs and you inject an amount proportional to the amount of carbs. This is called an Insulin to Carb Ratio (ICR). To correct, you test your blood sugar and then figure out how much you need to lower your blood sugar factoring in your Insulin Sensitivity Factor (ISF), that is how much you blood sugar is lowered by a unit of insulin.

Well the best way to figure out your ISF is an "experiment." During a fasted state, when at least 5 hours has passed since your last meal/snack or injection you test your blood sugar. Then inject a fixed number of units, I would would suggest at 2-3 units as 1 unit is not accurate. Then wait 2-3 hours and you should see the effect. That is a good first cut.

In the case of your ICR, you do a similar thing. When fasted, you inject a certain amount of insulin (say 2 units) and eat a known amount of carbs (like a glucose tab or two) and then observe how well your blood sugar returns to the same level it was before you injected. The rinse and repeat, when your insulin injection matches the glucose you can figure out how many carbs a single unit of insulin covers.

There are many things that can distort this experiment such as not having your basal set properly. While you may think you are using a huge amount of insulin, for a T2 eating a higher carb meal I don't think you are using a huge amount. A T1 may find that a unit drops them 50 mg/dl, but I actually find that at times a unit will only drop me 5 mg/dl. I find it particularly hard in the morning.

All this stuff is covered very well in books like "Using Insulin" by Walsh and "Think Like a Pancreas" by Scheiner. I would encourage you to check these out of your public library or just do what I did and buy them

Hi Sylster. I determined my ISF (Insulin Sensitivity Factor or how much one unit lowers your blood sugar) by trial and error. You probably already have some data. When I do a correction like you describe above, I keep careful records of how much I came down in three hours. Then after I'm sure that wasn't a fluke I start using that number (divided by the number of units you took) as my ISF and continue to keep records and tweak it as needed. You may in time find you have a different ISF for daytime and night time.

thanks for your repiles. I have purchased the Using Insulin by Walsh book and I already have the THink like a pancreas book. I was trying to use TLAP as a guide but it was confusing.I know in my gut that this is trial and error, I'm just afraid of the error!

That's why you always start conservative. I can't remember the numbers from your post about I:C but if 1:10 ends up time after time leaving you high at two hours you progress to 1:8 or even 1:9 to be safe and do that for a few days before reducing more. Using trial and error safely involves starting conservatively and going slowly, sitting with changes a couple days to make sure they aren't flukes.

I don't know about Think Like a Pancreas, but Walsh (who I love) does have lots of "formulas" that, I found don't hold true for all of us; I like his principals and trial and error better.

A controlled test is really the only way to find out, as Brian explained.

However --

There is one part of your description that raised a red flag for me. You say that you saw no effect for 3 hours after taking Humalog. Three hours is an awfully long time to see NO movement at all.

Consider another possibility. You may not be sensitive to Humalog. Analog insulins in particular exhibit distinct individual differences in response. A particular insulin can be efficacious for one person while being ineffective for another. For instance, Humalog does absolutely nothing for me -- I mean, nothing. It might as well be a placebo, whereas other insulins work just fine. So it does happen. The odds of this being the case for you, while low, are definitely finite.

It might be worth trying another fast acting insulin such as Novolog or Apidra, just to find out, or at least to eliminate the possibility.

Actually trial and error works just fine, David, it just takes longer. It also takes careful record keeping but I find I have lots of data about what didn't work very well which helps guide me to what will work. What I've found is that there is no "one right way" with Diabetes management! Lots of people swear by the formulas in a book like Using Insulin, I find they are too general for individual needs. YMMV.

Good point about the long flat period, but I'd also add that IR can change this dynamic considerably.

I've had very long peaks when the timing of digestion (effected by the mix of what I ate) and the timing/action of the bolus can result in this.

For a 50g carb meal, I will almost always have a net 50-60 mg/dl rise if I bolus just the right amount of insulin, finally settling back down where I started about 3-4 hours later. If the food is slow digesting, I can sit up there at the peak for an hour or two, and then start coming down.

For this reason, based on my preprandial BG and what I'm planning to eat, I adjust the timing of my pre-bolus so that when digestion starts, I'm in the 80s, that way I don't go over 140 most of the time.

If I start at 100, I'm heading for the 160's, even if I time the bolus just right. How long I'm up there depends so many things, but certainly glycemic index and quantity of fat/protein all have an impact.

I've eaten an 80g carb lunch (burger and fries) and apparently bolused just right to see nothing more than a modest rise up to 120, then back down into the 80s by 4 hours later.

I've eaten 30g and soared up to 170, even trying to plan it all perfectly. The only constant in this condition is variability :-)

I have no issue with trial and error, but as you say, it takes longer. The impatient speed freaks among us sometimes get impatient and want an answer sooner . . . LOL

And you're certainly right about published formulas. They are a starting point, nothing more.

yes, Dave, Diabetes is so variable and so much comes into play.

Slystr, there is a lot to learn when you are using insulin. Do not try to do it all at once. Brian's suggestions,, those of the other posters, and those in the both books are great starting points. Carb counting is essential and will help. It seems like a slow tedious process, and it is.. But you will learn how your body reacts to insulin and to certain foods. It will take time, many months for you to get so comfortable with the mechanics of managing diabetes. Take a little bit at a time, take a break form basal testing, then surge forward, one step at a time. All will work out, just takes time. Please do not get discouraged by what you perceive as "errors". I just call them "learning moments". You can take that info and use it to make decisions that will lead to better outcomes the next time.

God Bless,