A primer on intramuscular bolus injecting

Greetings all,
I am finding an ever-increasing need for faster bolus action. Whether it’s a missed pre-bolus (the piping hot meal in front of me and i haven’t bolussed yet), eating out in restaurants where i’ve no idea what or when i’ll eat, and my BGs are rising (at home i’d wait until they’re flat or trending down before starting to eat), or wanting to correct a hyper excursion, i’m getting fed up of waiting for my bolus to kick in. Sometimes it’s 20-30mins, but often it’s well over an hour … this morning i woke up at 9 (thanks to the Dawn effect), took a 2u, didn’t budge for 45mins, took another 2u, didn’t budge for another 45mins, then took another 1u (so i had c. 3.5u on-board by that point) - i then suddenly collaspsed, leaving me to gobble quickly to avoid a hypo. Perhaps that’s a slightly different topic, but either way, without Afrezza available in the UK, i feel i should explore intra-muscular injecting of Novorapid, to try to speed things up.
Is there a primer i can read somewhere? Or failing that, some do’s and don’ts to the process? which muscles? flexed or flaccid, or its doesn’t matter? how quick can i expect it to be? is the action of Xunits just as potent, only quicker-acting? or is it more potent than the same amount of subcutaneous injection? are there times it should be avoided? given the irritation of the latency (and associated risks) - why isn’t it an accepted practice/the norm? i.e. what is it about subcutaneous injecting that seems to be preferable?
Many thanks, as always, for your thoughts.

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The basics of it are 8 mm needles and using a muscle group with little fat on it. My son uses the calves, other members say the calf hurts and use other places like the delts. There will be some people by shortly with more information. Interesting question.

Interesting, thank you. Given the convenient location (close to usual injection sites), what about the abs? Perhaps there’s just a little too much fat there, although i’m rake thin (5’10 and 62kg), so not a lot of fat anywhere really.

I would imagine that if you are rake thin, that the abs would work just fine. It is really about getting a needle that is long enough. My son feels that the calf advantage is that he can exercise it pretty easily and unobtrusively if he wants even faster action. But that may just be his superstition. He does hate the highs though.

Feel free to ask more, or engage in this as a chat, but let me run through these quickly:

which muscles?

Anything you can get to easily. I like calves, shoulders, and thighs. But rotate like any other injection. Don’t use the same place over and over.

flexed or flaccid, or its doesn’t matter?

Relaxed!!! Tight muscles will hurt more.

how quick can i expect it to be?

It really depends, but you might turn in 20 minutes. Really you can’t always see a turn, because if you are rising quickly, part of the “turn” is that it’s slowing down the rate of rise. So it might not look like it is turning. But you just gotta trust me (and others who do it) on this - it’s faster!

is the action of Xunits just as potent, only quicker-acting? or is it more potent than the same amount of subcutaneous injection?

Same potency, insulin is insulin. Because it acts quicker, you might think the potency is different. But really, it is doing the same thing, but in a condensed time-frame.

are there times it should be avoided?

I do not think so. Maybe if you have a bunch of IOB and are worried about a crash.

given the irritation of the latency (and associated risks) - why isn’t it an accepted practice/the norm? i.e. what is it about subcutaneous injecting that seems to be preferable?

Endos are worried about lows. :roll_eyes: Or having dumb patients or people dropping too quickly and not knowing what to do. Who knows? Seriously, a BG of 65 used to be considered good. Now it is a frowny face on your endo report.

Sorry, just a quick run through, in a rush. Feel free to chat about these or ask for more detail.

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Not really an answer to your question, but is Fiasp available in the UK? Not everyone finds it faster, but for many (like me) there is a noticable speed difference. Using Fiasp has virtually eliminates the need to pre-bolus for me (I was pre-bolusing by 30-60 minutes before every meal previously).


This is interesting. I find my turn is variable (and agreed, it’s difficult to tell when rising fast, but it often varies from 20-60mins, or longer, when flat-lining). So 20mins would certainly be an improvement, particuarly if it is a more reliable 20mins (i often sit with a sliced piece of fruit, watching it go brown, waiting for my BG to turn)… although i did think it might actually be even quicker than that.

This is also interesting… but what are you inferring? That 65 is actually an okay reading? For years, my lower bound was around 64 (hence i would find 65 just about okay), but have been convinced (by my endo and nurses) to up it to c. 71, to avoid hypo unawareness and get my time-spent-low down. My stats tend to show too much time in hypo (6% < 64, 11% < 71) - so this is probably why.
I’m yet to be convinced of whether we are actually doing much/any damage by running at, say, mid-60s for hours on end…so long as we go no lower, but i’m open to the ‘hypo-unawareness’ argument.

Thank you for your other comments Eric, they were really helpful. I think i should probably just (carefully) experiment and see what happens. Shall report back once i’ve sourced some longer needles.


Thanks Jen, i hadn’t heard of it, but looked it up and it seems so. Your comments are interesting - i have asked my nurses if i can try a sample of it. Any ‘downsides’ to it, from your experience?


My understanding is that compared to subq injections, you do need to be more careful with IM injection sites, because muscles have important/larger nerves and blood vessels in them that can be damaged, relative to fat. So that’s probably also part of why endos don’t suggest it, and it’s why when you get IM injections from nurses, it’s pretty much always in a select set of vetted sites. That’s not say other sites can’t work, but they may have greater risks. For example, apparently the hip (ventrogluteal) is now considered safer than the butt (dorsogluteal) bc of risk of damaging the sciatic nerve in the latter. That said, the needles being used here may be short enough (these are shorter than standard IM needles, right?) that they are barely making it into the muscle anyway, just enough to work most of the time, but not so far as to have high risk of damage. I’d still be careful with site selection though. Nerve damage sucks.


I have spent a good part of my life below 70. I have no idea how much time, but a significant amount.

I do NOT have hypo unawareness. I generally know even before the CGM tells me (unless I am asleep).

I do not know if it just depends on the person. Maybe some develop it and some do not. But I can say that hypo unawareness is not guaranteed just because you spend a lot of time low. I did not develop it.

I think it is great at certain times. But it also depends on the circumstances. A flat 65 is wonderful. A dropping 65 is not. Unless it is time to eat, in which case a dropping 65 is wonderful.

I have said this to @daisymae many times - not all 65’s are the same…

One other important note!

If you do an intramuscular injection and then work the muscle a little bit, it will also help speed it up. Injecting in your leg and walking or jogging around will be faster than injecting and sitting.

Exercise increases blood flow to the working muscles, which is what you want to speed up absorption.

Here is a quick reference picture to show how much a little bit of exercise increases blood flow to the muscles. Look at the light blue, which is the blood flow to the exercising muscle. This compares rest (on the left) and exercise on the right for both an athlete and non-athlete.

(See reference link here)


Some people do have increased irritation with Fiasp compared to other insulins. This may be an issue for me, but it’s hard to tell, becuase I’ve had problems with reactions to infusion sets for years. Fiasp makes enough of an improvemnet to my life that I will stick with it even if there is an icnreased irritation problem.


You shouldn’t have trouble using it on MDI. Most of the problems people report are in pumps, as the additives can cause site irritation/insulin resistance when injected into the same spot for a period of time. I find it significantly faster and do not pre-bolus at all anymore. The downside is that it tails out quicker than NovoRapid, so you often have to combine it with a bit of R (Actrapid in the UK I believe) or a second dose an hour or two later to avoid a delayed spike.

Thank you all. I am attempting an ab muscle injection with a 4mm needle, which i would have thought is hitting it, but i’m not seeing much difference in speed just yet. I might switch to shoulders or biceps, but it’s a real pain getting undressed each time you want to bolus. Perhaps the calves are more suitable, but mine tend to be almost untouchably tight anyway due to my daily (mid-foot strike) running.

My endo wasn’t keen on giving me longer needles, arguing given my BMI i was likely already always injecting into muscle. This likely isn’t right, given i have been injecting into a ‘pulls’ of fat around my torso mainly…although the odd muscle might have been hit.

Right. I guess the time-in-the-syrem is also commensurately compressed (as well as time-to-‘turn’) ?So if SC injected Novorapid takes around 4 or 5 hours to wear off, what might this fall to with IM injection? 2 - 2.5hrs ?

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Thanks @cardamom. This doesn’t sound at all good. Are you able to share what you believe ‘good’ muscle sets are vs ‘bad’ ones, vis a vis avoiding nerve damage? And are you saying if only the outside of the muscle is hit (e.g. with shorter needles) the risk of this damage is lower?

Not my area of expertise enough to feel able to advise—I got my information about it by googling IM injection sites, and you can find information that way, but it’s somewhat variable. It’s pretty consistent that the deltoid is a relatively safe spot for example though (think where you get a flu shot and most other vaccines). My thought about the needle length was a personal guess, definitely not medical advice, just based on logic that the less muscle you hit with the needle, if using a shorter than standard IM needle, the lower the odds of both obtaining a true IM effect, but also of hitting nerves/blood vessels.

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Yes, duration is compressed as well.

I think in general though, duration is always harder to determine exactly. Possibly a little longer than 2 - 2.5 hours, but really difficult to know precisely.

Do you need a prescription for syringes or needles? In the U.S. you can get them without a prescription in almost every state. (Here, that particular item is regulated on the state level rather than federally).

All of that being said…

a) I think a 4mm needle is just not going to be effective.

b) I can get them with no prescription. And will gladly send them to you. Perhaps an exchange? Crumpets?!? :yum:


Last time I tried (more thank 10 years ago though), I was unable to purchase insulin syringes at the CVS pharmacy. I think New York State allows pharmacies to sell up to a 10 pack of syringes but CVS refused without a prescription.

We purchase ours off of Amazon. Screw the pharmacies not allowing you access to a life saving therapy. That sucks.


They may have changed it in the past 10 years.

Here is a state-by-state listing. (The Rx for insulin part is only referring to the old “R” and “NPH” stuff you can get at Walmart, not any of the new analogues.)

FWIW, there are only a few states that require a script for syringes or have some restriction like making you sign for them.

I think Amazon just follows the state law for whatever state the shipping address is in.

Try it!

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Jeez, New York, change your damn rules:

“The pharmacy can choose whether or not to require a prescription for syringes. If the pharmacy does sell syringes without a prescription, it can only dispense 10 syringes at a time, and it cannot give them to anyone under 18 years old.”

That is just a stupid rule.