How long before eating should you inject?

1980amyk said:

I was diagnosed in January this year and thought I was doing ok, I have recently started using the Libre and my levels rocket after I've eaten then come back to a normalish level after about 40 mins. My DN has said to inject just before a meal but I'm sure I've read that some people inject quite a bit before a meal. I'm doing a daphne course in October so hopefully that'll help but if anyone has any advice I'd be grateful.

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Yes, most people inject more in advance of meals, but you must find what suits you personally

Try moving your injection more in advance 5 mins at a time. That's what I did to find the right time to do mine.

I find breakfast needs to be the farthest in advance for me.

Edited to add that for people on analogue insulin, 15 to 20 mins in advance is common, but some people need more time, some less.

1980amyk said:

I was diagnosed in January this year and thought I was doing ok, I have recently started using the Libre and my levels rocket after I've eaten then come back to a normalish level after about 40 mins. My DN has said to inject just before a meal but I'm sure I've read that some people inject quite a bit before a meal. I'm doing a daphne course in October so hopefully that'll help but if anyone has any advice I'd be grateful.

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I think it also depends on exactly where you are injecting (and I don't mean on the train or in the supermarket). If you inject in your leg it takes a bit longer to get started than if you inject in your stomach. Personally I aim for 10-15 minutes if injecting in the stomach area.

I inject 5-10 min before eating depending on where I'm at to start. BF needs to be closer to 10. Stupid as it sounds I set my oven timer for 5 min then make my meal. However I am VLC and this makes a difference. I think it would depend on the meal, BF is always a **** shoot even though I eat the same thing. The only carbs are a piece of lettuce or a few celery chunks and the rest is fat ( avocado and or mayo) and I still go up most days. If I inject too early I will go down 1 st and then up. It also depends how active I am in the morning as that will raise me.

For some reason my insulin takes longer to "get going" in the morning than at any other time. If I have a carb heavy breakfast (e.g. cereal, porridge or muesli) I need to inject 30 to 40 minutes in advance to avoid a spike and remain completely stable. This is fine for me as I've now just worked it into my routine; I inject the moment I wake up, then have a shower and get ready for work and eat 30 minutes later. Your experience may vary (especially because some people report that a shower speeds up their insulin absorption; it seems to have no effect on me).

For lunch I generally have a low carb salad and for that I find that injecting just a few minutes before is fine.

For dinner, I aim for 20 to 30 minutes in advance for (what I consider) a "regular"/balanced meal (c. 40 to 50g of carbs). If I am having a pizza, take-out or other very high-fat food then I find that the fat delays any spike so the timing in advance is less important.

I have a Libre so can follow the graph. I find that even 30 minutes is not enough to prevent a spike in the morning but also a shower can increase the reading. I would guess that everyone is different so trial and error is needed. At least Libre allows you to closely monitor this.


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You can use your libre to figure out when to inject - so inject and wait until the graph starts to curve down, indicating insulin is working, then eat - but if you do that you have to bear in mind that the libre is testing interstitial fluid, which runs 15-20 minutes behind what your blood sugar is doing, so you don't what to be starting off your injection at too low a level and you will need to be ready to eat right as the curve hits - you can't really leave it another 5 minutes or forget once it's started dropping or you might drop too low and hypo before you start digesting your food, which will, frustratingly, undo the aim of the prebolus and cause a spike anyway because you will either have to take on additional carbs to treat the hypo or the hypo will cause a liver dump and spike.

That's a really long (and poorly punctuated) way of saying; pre blousing is good to reduce post meal spikes, but cautiously experiment with it to find the best way of getting it to work for you. Hopefully the libre will be a really good tool to help with the experiments.

I bolus 20-25 mins before breakfast and 20 mins before lunch and dinner, if the meal is high in fat I inject 10 mins before but used a split-dose on MDI but now use a Dual-Wave bolus on a pump.

I experience dramatic differences depending on food content. High fat, high protein meals with between 5 and 10g of carbs I bolus just before eating and stay flat.

Anything with a higher carb content, less protein and fat it can be between 30 and 45 mins.

The key is to test different foods and work it out for yourself.


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1980amyk said:

I was diagnosed in January this year and thought I was doing ok, I have recently started using the Libre and my levels rocket after I've eaten then come back to a normalish level after about 40 mins. My DN has said to inject just before a meal but I'm sure I've read that some people inject quite a bit before a meal. I'm doing a daphne course in October so hopefully that'll help but if anyone has any advice I'd be grateful.

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Hi, I normally inject just before a meal, unless BS is a bit higher, then I would inject in advance. Also if my BS is in the 4's or 5's before a meal, then I inject just before eating.