Whether to target 2 hours after food or the acting time of bolus for readings in normal range

I am on a basal-bolus regimen for the past 6 months approximately (NovoRapid+Levemir). When I go to doctor for check-up or get my blood sugar levels tested in laboratories, the tests are always made 2 hours after food. But from personal experience I have found that if I target achieving blood sugar in the normal range 2 hours after food, I invariably have a low before the acting period of the bolus ( 4 hours approx.) ends. So is it a good idea to target normal blood sugar level after 4 hours instead of the conventional 2?

I take 2 shots of Levemir instead of a single bed-time shot as advised by doctor because it gives me better control. But I find that Levemir reduces the blood sugar level by 20-30 mg every hour. So even if I have normal sugar levels at the end of the acting period of my bolus, Levemir invariably takes me to a low during night time due to the long gap.

I am skeptic about taking something to eat at bed time because that would ensure that my sugar remains out of the normal range for longer.

I might be totally speaking crap, not knowing what I am speaking. So I appreciate comments, suggestions and your experiences.

Continue to target your BGs to be within normal range within 2 hours postmeal. If you are crashing before then, most likely, you have some kind of insulin imbalance going on with your meal, most likely with your novorapid bolus.

I would suggest testing a couple of times before 2 hours postmeal, to see where and what your postmeal spike actually is. If you are eating a carb-rich meal, it's possible to spike high and crash before the two hour mark.

You just need to gather a bit more information about your BG profile to determine what coure of action you need to take.

I have to tell you, your basal insulin (Levemir) should keep your blood sugar flat, not constantly dropping. Dropping 20-30 mg/dl every hour is a sign that your basal insulin is too much. I would suggest talking with your doctor about adjusting it.

In the long term, it would be good to learn how to properly adjust your own insulin. The book "Using Insulin" by Walsh gives a good description in his book, he also has a description on his site.

And while it is good to be back in normal range at 2hrs after your meal, if you are already back at your premeal reading, you may still have enough insulin remaining in your system to drive you low.

I agree your basal sounds high, and I would work on adjusting that so you are where you want to be not only on waking and at bedtime, but between meals.

I always test and correct if necessary at the two hour mark, so as not to remain high very long. But it's really important to take your Insulin on Board into account. If you don't do that, you will go low. Also, you need to be sure your ISF is correct. For me, it's easier because I'm on a pump but I did the math for two years on MDI.

So, for me my ISF is 40 - One unit of insulin will drop me 40 points. I figure my duration at 3 hours. I'm using Apidra which is the fastest insulin, you will probably have more like a 4 hour duration. So if you take 4 units at 1PM for lunch and you test at 3PM and are 200. If your target is, let's say 120 you are 80 points high. If your ISF is 40, that means you need two units to correct. However, you still have two units of insulin on board. (4 units for four hours, means at 2 hours 2 units are still acting). So you wouldn't do a correction, in order not to go low. If you had been 240, and so needed to come down 120, that computes to 3 units needed. You only have 2 units still active, so in that case you would take one unit. Make sense?

If you haven't already done so, you can figure out your ISF by trial and error. Start conservative - say 1 unit only lowers 20 points, and if you are still high, figure out by how much and keep the records, till you inch it up to the right number.

Zoe - Good job illustrating with a concrete example. I do have one question, however, about your advice.

As far as setting the ISF and starting out conservatively, wouldn't it be safer, or more conservative, to assume an ISF of 1:60 instead of 1:20? The 1:60 ratio would yield a smaller insulin correction than a 1:20 ratio. Then one could inch up to 1:50, 1:40 and so on.

I think I know what you intended but you may have stated it incorrectly. Am I missing something?

Oops, no you are absolutely right, Terry!That's why I always give concrete examples because I get lost in the terms like "higher and lower". And I thought I was good at math!

Guruprasad - for determining ISF in a safe fashion....what Terry said!!

Hello -

If your Levemir is dropping you 20-30 mg per hour then you are using too much basal insulin. Your basal should keep you within a 30 point range (+ or -) without eating if it is reasonably set. By cutting back on your basal you'll be able to be more aggressive up front with your bolus without having as much risk of going low later.

Good luck,


Some 4-5 months back my ISF was somewhere around 30-40 mg per unit of insulin. But I have had severe illness and been hospitalized once after that. So it does make a lot of sense to re-calibrate the ISF and get the bolus dosage as close to perfect as possible.

I suspected the same, but this morning the basal insulin dropped me from 129 mg at 00:30 hrs to 62 mg at 05:30 hrs, roughly bringing down 12-13 mg per hour. I still feel I can adjust the basal dose to a slightly lower value and get better results.

I already have Walsh's wonderful book and I refer it whenever I have some doubts. I will test often and experiment with the insulin dosages to find out what works best for me. Thanks for the advice.

After two hours you will still have insulin working. You need to know the duration of the insulin (for your body). You need to know how much one unit of insulin drops your blood sugar. If your duration is 3 hours, after 2 hours your blood sugar is 100 and one unit of insulin drops you 30 points, you would be cutting it tight but would not crash at 70. In our case where duration is 3.5 hours and one unit drops her 70 points, a normal blood sugar in two hours means you have to feed the insulin. We give 8 grams for each unit left on board. Knowing your duration and how much one unit drops your blood sugar will allow you to make the correct decision at the two hour mark (also how much each gram raises your blood sugar).

Trying to figure out that number. Previously 1 unit per 12-13 g of carbs seemed to work but now is erratic. Same food insulin shot doesnt result in similar bg levels. That is a problem for me. :frowning:

For testing like that, I think that it's best to do it as scientifically as you can, with a definite "known" amount of carbs. I eat pretty much the same thing every day for breakfast and lunch and I think that it makes it easier to spot it when ratios need tweaking because Jupiter is in line with Mars or whatever makes it change? I also think that it helps if the "known" amount is < 20, as then a "mistake" doesn't have as much potential for crazy swings?