Hello - I was diagnosed as T1D 3 weeks ago. My GP told me to test my blood glucose levels both before and 2 hours after every meal. I saw the diabetes specialist team today and they told me to test 4 hours after my last mouthful. Conflicting instructions! 4 hours seems rather excessive, especially in the evening - if I don’t finish my evening meal by 7pm or 7.30pm it’s going to be a very late night. Grateful for people’s thoughts. Thanks.
When to test?
- Thread starter rupertl
- Start Date
I would take a step back and think about why you are testing and what you are going to do with the results.
Typically, I test when I wake, when I go to bed and before every meal.
The reason for this is to take the results into consideration when calculating my insulin dose.
Advice to test 2 hours is common for type 2 to work out what is the impact of various foods to decide whether to continue eating or to avoid in the future. With type 1, most people do not need to restrict their diet as long as they correctly calculate their insulin dose.
I have not heard advice to test every 4 hours.
Typically, I test when I wake, when I go to bed and before every meal.
The reason for this is to take the results into consideration when calculating my insulin dose.
Advice to test 2 hours is common for type 2 to work out what is the impact of various foods to decide whether to continue eating or to avoid in the future. With type 1, most people do not need to restrict their diet as long as they correctly calculate their insulin dose.
I have not heard advice to test every 4 hours.
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The 2 hours is very useful to see if your insulin dose for your meal was correct, so you can change your dose or your food next time.
I think the 4 hours is because mealtime insulin lasts for about 4 hours, so if you're still high after that time you know there's no more mealtime insulin going around to reckon with if you want to correct.
I think the 2 hours test is way more useful.
And don't forget to test before and during driving and physical activity as well! Th driving for safety reasons, the activity because that might have a big impact on your numbers.
Good luck!
I think the 4 hours is because mealtime insulin lasts for about 4 hours, so if you're still high after that time you know there's no more mealtime insulin going around to reckon with if you want to correct.
I think the 2 hours test is way more useful.
And don't forget to test before and during driving and physical activity as well! Th driving for safety reasons, the activity because that might have a big impact on your numbers.
Good luck!
Hi, @rupertl , as you've been dx'd T1, I assume you've been put on insulin straightaway, presumably two types, a slow acting "basal" insulin to cover background needs, and a fast acting "bolus" insulin to inject with meals?
If that is the regime you are on, then the gp is wrong, and the consultant is right.
That is because the fast acting bolus insulin you take for meals will typically last for about 3 to 5 hours.
There are differences between different types of insulin but generally speaking, they get to work in about 20 mins, reach peak action in about 45 to 90 mins, and wear off over 3 to 5 hrs. As you can see from the timing ranges, there are broad margins, it's not a definite science, and it varies widely between individuals and on meal types and many other factors.
Bearing in mind that they tend to have an overall effect of 3 to 5 hrs, what they are trying to figure out in these early days is how to get you into a situation where you check your bg just before the meal to see what level you're at, take the injection, then if the amount of the dose and amount of food are correct, the level about 4 hours later when the insulin wears off should broadly match and leave you where you started. If they don't it'll give your team pointers on adjusting the dose.
The advice to test after 2hrs is incorrect as it will tell you nothing about what effect that injection is having on you in the remaining 2 or so hours of action, so you will have no idea whether the dose was about right or not at the point it matters, which is when it wears out.
Where you are after 2 hrs doesn't really matter in these early days. As time goes by you'll maybe learn some more sophisticated techniques to correct inter-meal, but forget about that at this early stage.
If though, you feel hypo (bg too low) at any time before 5 hrs is up, then definitely test.
I suspect your gp is more accustomed to treating T2, but the biology and factors to be taken into account are completely different for the two conditions.
If that is the regime you are on, then the gp is wrong, and the consultant is right.
That is because the fast acting bolus insulin you take for meals will typically last for about 3 to 5 hours.
There are differences between different types of insulin but generally speaking, they get to work in about 20 mins, reach peak action in about 45 to 90 mins, and wear off over 3 to 5 hrs. As you can see from the timing ranges, there are broad margins, it's not a definite science, and it varies widely between individuals and on meal types and many other factors.
Bearing in mind that they tend to have an overall effect of 3 to 5 hrs, what they are trying to figure out in these early days is how to get you into a situation where you check your bg just before the meal to see what level you're at, take the injection, then if the amount of the dose and amount of food are correct, the level about 4 hours later when the insulin wears off should broadly match and leave you where you started. If they don't it'll give your team pointers on adjusting the dose.
The advice to test after 2hrs is incorrect as it will tell you nothing about what effect that injection is having on you in the remaining 2 or so hours of action, so you will have no idea whether the dose was about right or not at the point it matters, which is when it wears out.
Where you are after 2 hrs doesn't really matter in these early days. As time goes by you'll maybe learn some more sophisticated techniques to correct inter-meal, but forget about that at this early stage.
If though, you feel hypo (bg too low) at any time before 5 hrs is up, then definitely test.
I suspect your gp is more accustomed to treating T2, but the biology and factors to be taken into account are completely different for the two conditions.
Last edited:
As the OP @rupertl has not put what his medication is in his / her profile / signature, I erred on the safe side and I posted what I did as a T2.
I’m on a basal dose at the moment, so the four hours after food before bed and comparing that to my morning reading makes sense. Have also been told to start a Bolus dose at meals now as well.
ImSpiritus
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If I were to follow the "normal" guidelines of inject 15 mins prior then test 2hrs after then my BG will always be high. For me the biggest drop is at the 3hr after food.
kitedoc
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As always @ImSpiritus, it depends.
Answering from experience as a T1D, not as health professional advice or opinion:
And this is testing with a blood glucose meter not with Continuous Glucose Monitoring (CGM) -
I assuming that outside a hospital the best single BSL estimation is that performed on an accurate meter
(+/- 5 % error rate) with proper technique.
A bolus is assumed to mean a dose of short-acting insulin given before a meal
As always, interpretation from your health team is advised, the following are only suggestions from
my own observation on myself.
Single BSL testing time:.................................Advantages....................................................Disadvantages...............
early morning e.g. 3 am..........................detect DP *and manage it.....................................sleep disturbance..........
...................................................................or part of basal testing.**......................................"...........".....................
episodic: every 2 hours for.........................basal testing**...................................................sleep disturbance...........
6 to 12 hours...........................................................................................................................& sore fingers !............
on waking........................................high result ? DP* ? insufficient.........................?.blood on work clothing!........
................................................insulin overnight? ? hypo overnight., ?other...............................worry.......................
.......................................low result? too much insulin overnight ? hypo? other..........................worry.......................
................................normal result ?no DP*, ?DP Mx OK, ?overnight insulin OK? other
before breakfast..........................higher =? DP,* effect or lower +? other....assumes accuracy of insulin: carb ratio#
...................................................... or to calculate insulin:carbs ratio#.............which can vary for many reasons.......
> 90 minutes to...................................measure effect of the carbs***vs .....................finding the optimal timing....
210 minutes after ............................insulin bolus and other effects on BSL . .................for meaningful results.......
bkfst, lunch and dinner........................normal = ?proper insulin:carb ratio plus.........................................................
.................................................................for other effects and factors.....................once established = less testing...
.................................................. .above or below range = ?incorrect.........but needed again if illness, change
......................................................insulin:carb ratio# +/- other effects/factors..........in diet , insulin and other.........
About 4 hours after.....................low BSL or high ? incorrect insulin:carb ratio.........more ouches !!.......................
a meal..........................................measure effect of low carb higher protein fat meal................................................
........................................................vs insulin and other effects/factors......................................................................
.................................................+/- use of soluble insulin bolus vs other insulins.......................................................
.
1 hour before exercise.........guidelines suggest not exercising for BSL > 14 mmol/l..... bleeding during exercise!!
......................................................................or < 4 mmol/l (obtain individual advice)..............................................
During exercise.........................to gauge how well pre-exercise Mx is working.........inconvenience, bleeding etc
...................................................and warn of hypos or hypers...................................................................................
After exercise - immediate .....to gauge end result, about fitness to drive, warn of hypos.........as above !................
~ 6 hours after exercise......................to detect hypo and act accordingly.......................................sleep.............................
and overnight..............................................................................................................................................................
SO ... one day: DP test plus all before/after meals, 3 for the first 6 hours of basal testing
plus 3 for exercise = 14 test strips.
* Dawn phenomenon: see Home page: type it in question box upper right
** basal testing - also use Home page, question box
Mx = management
*** - some include a % of protein intake in their carb count
# - insulin:carb ratio: many people work out for so many carbs in a meal what amount of insulin bolus
(short-acting insulin) they need to give to ensure acceptable BSL results after the meal
(too high BSLs = damage long-term, too low = hypo risk)
The ratio may differ from one meal to the next in the day.
Answering from experience as a T1D, not as health professional advice or opinion:
And this is testing with a blood glucose meter not with Continuous Glucose Monitoring (CGM) -
I assuming that outside a hospital the best single BSL estimation is that performed on an accurate meter
(+/- 5 % error rate) with proper technique.
A bolus is assumed to mean a dose of short-acting insulin given before a meal
As always, interpretation from your health team is advised, the following are only suggestions from
my own observation on myself.
Single BSL testing time:.................................Advantages....................................................Disadvantages...............
early morning e.g. 3 am..........................detect DP *and manage it.....................................sleep disturbance..........
...................................................................or part of basal testing.**......................................"...........".....................
episodic: every 2 hours for.........................basal testing**...................................................sleep disturbance...........
6 to 12 hours...........................................................................................................................& sore fingers !............
on waking........................................high result ? DP* ? insufficient.........................?.blood on work clothing!........
................................................insulin overnight? ? hypo overnight., ?other...............................worry.......................
.......................................low result? too much insulin overnight ? hypo? other..........................worry.......................
................................normal result ?no DP*, ?DP Mx OK, ?overnight insulin OK? other
before breakfast..........................higher =? DP,* effect or lower +? other....assumes accuracy of insulin: carb ratio#
...................................................... or to calculate insulin:carbs ratio#.............which can vary for many reasons.......
> 90 minutes to...................................measure effect of the carbs***vs .....................finding the optimal timing....
210 minutes after ............................insulin bolus and other effects on BSL . .................for meaningful results.......
bkfst, lunch and dinner........................normal = ?proper insulin:carb ratio plus.........................................................
.................................................................for other effects and factors.....................once established = less testing...
.................................................. .above or below range = ?incorrect.........but needed again if illness, change
......................................................insulin:carb ratio# +/- other effects/factors..........in diet , insulin and other.........
About 4 hours after.....................low BSL or high ? incorrect insulin:carb ratio.........more ouches !!.......................
a meal..........................................measure effect of low carb higher protein fat meal................................................
........................................................vs insulin and other effects/factors......................................................................
.................................................+/- use of soluble insulin bolus vs other insulins.......................................................
.
1 hour before exercise.........guidelines suggest not exercising for BSL > 14 mmol/l..... bleeding during exercise!!
......................................................................or < 4 mmol/l (obtain individual advice)..............................................
During exercise.........................to gauge how well pre-exercise Mx is working.........inconvenience, bleeding etc
...................................................and warn of hypos or hypers...................................................................................
After exercise - immediate .....to gauge end result, about fitness to drive, warn of hypos.........as above !................
~ 6 hours after exercise......................to detect hypo and act accordingly.......................................sleep.............................
and overnight..............................................................................................................................................................
SO ... one day: DP test plus all before/after meals, 3 for the first 6 hours of basal testing
plus 3 for exercise = 14 test strips.
* Dawn phenomenon: see Home page: type it in question box upper right
** basal testing - also use Home page, question box
Mx = management
*** - some include a % of protein intake in their carb count
# - insulin:carb ratio: many people work out for so many carbs in a meal what amount of insulin bolus
(short-acting insulin) they need to give to ensure acceptable BSL results after the meal
(too high BSLs = damage long-term, too low = hypo risk)
The ratio may differ from one meal to the next in the day.
kitedoc
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- black jelly beans
