Pros and Cons of intramuscular insulin injections?

Hello everybody how are you today?

My question is, is there any benefits or let’s say ‘different’ characteristics of intramuscular insulin injections vs subcutaneous?

I read somewhere that the absorption is quicker… but then I read on Facebook someone saying it is slower


I love them, and I find, mostly, they’re faster. I assume when they’re not, it’s because I didn’t get the muscle. I’m not sure why someone would find them slower unless they also didn’t hit muscle. In general, I consider them a more substantial shot of insulin. Sub-cutaneous shots now feel painfully slow in comparison. However, before I ever tried my first IM, I had learned how to speed up a sub-q shot just by mixing injection and activity. For me, a shot along with 5-10 minutes of moderate activity would almost be the same.


They are quicker. Especially if the muscles used are working after the injection.

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@Israel. The only comments I have second @Nickyghaleb and. @Eric s comments.

Faster absorbtion, especially if it’s a large muscle and in use, and generally more comfortable with boluses under 15u


For my son they are quite a bit faster, perhaps by as much as 30 minutes when trying to turn a stubborn high.

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Personally I have never done one, and don’t plan to, since I have Afrezza.

But wondering the benefit of 30 minutes sooner compared to not IM is that significant? I was thinking IM was both in and out quicker, lower peak.
Is that true?

For us IM is faster and also “more insulin”: you get a stronger effect than subcutaneous. So, theoretically you should use less if you were sure it would work as an IM.

But—I a recent IM thread here on FUD, most participants also wrote that the IM effect was not totally reliable: sometimes it works, sometimes not. For us, we use 12.7 mm needles for IM, and out success rate is about 50%. We use thigh and calf, and run for 5 minutes after injection.

@MM2, do you mean less insulin tail? It is very possible, but we never thought of measuring :frowning:

Note: the IM thread I mentioned above is here:

IM insulin injections: what techniques work best for you?


I’m new to insulin usage, only a few months now but I did try IM a fews times last 2 weeks.

It hits like a MACK truck in my case. I take Humilin R (30 mins offset) and normally 10UI in the AM and 10UI before dinner and maintain 100-120 very well. But recently I’ve had 280-300 spikes and decided to try IM.

Caution! Few days ago after only 10IU IM, I went from 285 to 70 in about 20 minutes which didn’t feel good at all. Instead of regular meal, I had to consume 100g of glucose before things started to get back to normal. After an hour I was back to about 120.

Word of caution, for a stubborn high, I could see the benefit but the dose must be adjusted accordingly. in my case 5IU would’ve been sufficient.

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I use a variety of shots now but definitely avoid large boluses I’d not doing a regular sub-q shot. I have found that IM shots are often best as a catalyst of sorts, just something to get me turned in the right direction again, but that only a fraction of a full bolus is needed like that. In fact, I usually want to avoid 10 units hitting all at once… only because I rarely need that much all at one time. If I think I need 6 units to cover a high blood sugar, I’ll often do 2-3 units via IM and do a sub-q shot of the remainder at the same time. I have absolutely no idea if it’s doing what I think it’s doing, but somewhere in my mind, it’s a way to get some fast acting insulin while putting some away a little for later.

I do think it’s amazing stuff, but I also think you have to be very, very careful. And start conservatively. I think running a little higher while you try to learn the action of your insulin is probably preferred to dropping too fast and experiencing a dangerous situation.


Makes a lot of sense @Nickyghaleb, kinda of the way I looked at it too; make R act a littler faster and get the best of a “lower dosage”. A few times subq @10IU didn’t seem to affect my BS at all even past the 30 minutes mark. I even started questioning if my insulin went bad :slight_smile: .

Again, I’ve only been on insulin for 4 months now and still adjusting, but with my “lifestyle”, a faster response seems to be easier to manage and also helps with the crashes I’ve been struggling with.

I’m going to taper down and gradually find the right dosage.

Thanks for all the comments, this is really helpful!

@Nickyghaleb is your pump I’m too? Or only IM for high corrections?

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@elver, if my pump is IM, then that is completely by accident. :grin:

No, I do them for high corrections and if I’m gearing up to eat something bad. :roll_eyes:

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I’ve done that many times. I still do from time to time. I think though that when the bolus I know should work doesn’t work, more often than not, it’s because it’s not enough insulin. I might be wrong here, but I think if 3 units is exactly what I need to bring down a certain high BG, and it’s not bringing it down, it’s because there’s something else at play that has increased the amount of insulin I need… the insulin is working fine. I just need more. But this is where it gets tricky for me, and I do have a terrible and nasty little habit of insulin stacking. I do a shot, I want it to work now, so when it doesn’t, I do another shot. It doesn’t do too much for the immediate problem and can often be setting me up for another problem in the near future. That insulin is working, so I have to be very careful with how I proceed.

I feel like I’m lecturing you, and I don’t want to do that, but I get very nervous talking insulin dosing through this form of communication. There’s too much information missing on both sides. So I would like to emphasize, especially as you’ve only been doing insulin 4 months, that insulin, when done in overabundance, can have swift consequences. I’ve made some mistakes, and I’ve startled myself. I also don’t want to encourage fear… I really don’t. Insulin is the best stuff on earth. I just hope, especially as you move into different strategies, you are being safe.

Sorry for momming you. :grimacing:


One scenario is that your insulin is working exactly as it should, but your blood sugar is also simultaneously rising, so they balance each other out and you are holding steady so you think the insulin isn’t working. Personally, when using Humalog or even Fiasp, I would not expect to see a change at the 30-minute mark. I would give a correction at least an hour to start working, and with an overnight high I would only expect to see my CGM line turn downward after about two hours – two long, frustrating hours, mind you.

Wowzers! My first few IM shots I only did 1 U, just to see how it affected things. I don’t do them often, but even now, 3 U is the max. More than that and I would expect to be staring into the jaws of death.


Keep in mind meter bg can be off, especially in higher range. Your 285 may have been 220.

You are using R, which is a short-acting insulin. Instead of trying to do IM injections with R, why not talk to your doctor about trying a rapid-acting insulin like Humalog, Apidra, or NovoRapid/Novolog? Rapid-acting insulins have a peak time of about 90 minutes compared to 2-4 hours for a short-acting insulin. There’s even an ultra-rapid acting insulin in Fiasp, which has a peak time of 60 minutes. Or an ultra-, ultra-rapid acting inhaled insulin in Afrezza (though I have zero experience with that). There are a lot of options out there that are much faster acting than R.

@Nickyghaleb I tend to have larger boluses, so when I do Im corrections I will split them up. That way I don’t have a huge bolus trying to be absorbed, and instead have 2 to 3 small boluses all working in tandem. Similar to stacking, the bolus can knock you sideways if your math is off, or it can be a turbo charged bolus when everything is perfectly aligned

can IM insulin injection be done using the pen (4mm needles)? that is not using a long needle syringe? I don’t have long needles. If I injected my Novolog Pen into my biceps would it speed up the absorption? Does pen injection into biceps or calves count as IM?

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IRC from flu shots and, also, having accidentally IM’ed insulin you need 10mm (1/2 inch). The bottom line if you are doing it intentionally is that you need to know how much fat you are carrying; I think I could do an IM with a 4mm needle into my bicep, but if I did so I would ram it in and hold it down while pressing the button, or the plunger, as appropriate.

On the more general topic, whenever I’ve done it I have found the results weird. That’s almost certainly because of what I’m used to - I know what a SubC does through bitter experience and that is the devil I love, though I may not actually know it.