Bolus timing vs insulin:carb ratio

[TwilightMidna]

Another day, another question!

Is there a way to tell if a spike after a meal is caused by the bolus timing or an incorrect insulin:carb ratio? Presumably the answer is just to experiment but I'm wondering if there's a pattern I could look out for with my blood sugars/on my Libre graph that might give a clue as to which is the issue? Is there anything else to consider when trying to address a regularly occurring spike?

Thanks everyone 🙂

 

[Inka]

@TwilightMidna The first question is how high are you spiking? Some spikes are normal. Also, during the honeymoon period, your own insulin often kicks in a bit late anyway so if you aim too low, you’ll be prone to hypos.

I’d look to see if and when you’re coming down and to what level. If you’re coming down ok, but spiking too high, then I’d try cautiously altering the timing of your bolus. You’ll probably find different meals (ie breakfast, lunch, etc) need a different amount of advance bolus time.

 

[rebrascora]

Hi. It is a good question and basically, if your levels have come back down more or less where they started before your next meal, then the ratio was right, but if you spike high in between, the timing was wrong. If you go up and don't come back down (near enough) to your starting point (or go too low) then the ratio was wrong.
So, say your pre breakfast reading is 6.8 which is in range so no correction required and you inject your breakfast bolus and have your breakfast 20 mins later and your levels shoot up to 18 but by lunchtime (or 4 hours later, they are back down to 7 then your ratio was right but the prebolus timing was too short and you need to give it 5 mins longer the next day and see how that works and maybe try another 5 mins longer still a couple of days later, until that spike starts to come down to an acceptable level.
If however, you are 6.8 before breakfast and you inject your bolus and spike up to 18 and then only come down to 12 by lunchtime, then your ratio was probably wrong. You may also need to adjust the timing, but you would adjust the ratio first and see how that worked out and then adjust the timing once you get the ratio right, so that your levels are back down to premeal levels by the next meal or 4 hours later.

It is wise to test any adjustment for a couple of days to see if you get reasonably consistent results before changing anything again and only ever change one thing at once.
It is also very important that your basal insulin is correctly adjusted BEFORE you mess with ratios or timings.

 

[helli]

Confusingly, there is another parameter which can affect this - your BG when you take your bolus.
Some bolus insulins are more dependent on this that others - I find Fiasp more dependent on my BG than NovoRapid was when I took it. But regardless of your bolus insulin, if your levels are high (this varies for different people but for most it is anything over 12 mmol/l), we become insulin resistant. This affects how slow our bolus is to start working and how much we need.

 

[rebrascora]

If you can post some photos of typical Libre graphs showing any spikes you are concerned about then we might be able to advise better.

Just as an example, when I was first diagnosed and using insulin, my levels used to spike up to 15 almost every morning and then come back down into range. Gradually I experimented with the timing and found that I actually needed to prebolus Novo(not so)Rapid a whopping 75mins in advance of breakfast. and 30 mins at other times of the day. I swapped to Fiasp, but most mornings I still need 45mins prebolus time to prevent spiking above 10. This is quite extreme but it gives you an idea of how significant the prebolus time can be. There are other people who would hypo 5 mins after injecting, so you need to find the timing that works for you by slowly increasing the timing a few mins at a time until you find the sweet spot for you.

 

[TwilightMidna]

That’s all so helpful, thank you!

So I’m usually starting in the 5s and (depending on what I eat) spiking to 10/11/12. Breakfast seems to be the biggest issue whereas for lunch/dinner I might “spike” but still be in range. It’s hard to find a typical graph as they’re all so different… I like to walk after my breakfast which I assume is another factor to consider.

Regarding the basal - the Lantus seems to keep me steady overnight at 4.4-5.6 generally, but sometimes that makes me anxious as it feels a bit too close to being low. I’ve only had one genuine low though since starting on insulin in August. I tried decreasing the Lantus by one unit but then my blood sugar seemed to rise between meals. Is there a way to get it to keep me steady at a higher level? Would reducing my insulin at dinner help with that?

I’m having a snack before bed, partly to keep the Libre happy - it seems to read a bit low for the first 4/5 nights when I lie down (not compression lows - I’m lying on the other side of my body to the Libre). The other reason is because I need to put on weight. I’m not bolusing for the snack (15-20g carbs).

Thanks and sorry for writing so much. Not sure how much of that is relevant !

 

[Inka]

10/11/12 isn’t a bad spike @TwilightMidna and you come down nicely. Regarding your Lantus, I agree. I wouldn’t want to be quite that low overnight. Nocturnal hypos are scary. Even on a pump, I like to be in the high 5s minimum.

There’s an obvious answer to your issue about reducing the Lantus to make you ok during the night but then feeling your daytime control is a bit out: change to a twice daily basal! You can then have as much as you need to keep control during the day and as little as you need to avoid running too low overnight. Levemir is a twice daily basal as are the isophanes. So much more flexibility 🙂

 

[TwilightMidna]

Thank you @Inka. Good to know that the rise after breakfast isn’t too bad. Yes it does come down pretty well before lunch (apart from the few days when I tried to adjust my basal!). I have been wondering about the twice a day basal as had read about it in posts here. I’ll mention this to my doctor next time we catch up. Thank you again!

 

[everydayupsanddowns]

Thank you @Inka. Good to know that the rise after breakfast isn’t too bad. Yes it does come down pretty well before lunch (apart from the few days when I tried to adjust my basal!). I have been wondering about the twice a day basal as had read about it in posts here. I’ll mention this to my doctor next time we catch up. Thank you again!

As the effect is more pronounced at breakfast, it may be that your liver is gleefully adding a little confusion into the mix with some Dawn Phenomenon or ‘foot on the floor’.

Quite often during the year I have to add roughly an extra unit to my calculated dose to look after my liver’s nonsense. I can’t effectively do it with ratio, because some breakfasts I have are twice the carbs of others, but my liver dump (when it happens) is fairly consistent.

 

[rebrascora]

As the effect is more pronounced at breakfast, it may be that your liver is gleefully adding a little confusion into the mix with some Dawn Phenomenon or ‘foot on the floor’.

Quite often during the year I have to add roughly an extra unit to my calculated dose to look after my liver’s nonsense. I can’t effectively do it with ratio, because some breakfasts I have are twice the carbs of others, but my liver dump (when it happens) is fairly consistent.

Yes, my liver consistently needs 1.5-2 extra units on a morning regardless of whether I have breakfast or not, so I don't change my ratio to incorporate it, but treat this as a correction in advance, to help my basal in the morning, rather than anything to do with my breakfast bolus or my ratio, even though I inject my breakfast bolus at the same time ie as soon as I wake up and before I get out of bed. If I don't have breakfast, I still need that 1.5-2 units of Fiasp even if I wake up in the low 4s. I use 1.5units at that level but anything above 5 needs 2 units and above 7 gets a correction dose added in as well.

 

[TwilightMidna]

@everydayupsanddowns now that you mention it, I have noticed that my blood sugar rises a bit between getting out of bed and sitting down for breakfast. I hadn’t really considered that this might have a knock-on effect on breakfast. Definitely something to think about! Thanks!