I need a refresher on proper syringe usage

I’ve only been doing this for 43 years, but I find myself getting sloppy and there are some things I just don’t know. (I’m MDI)

What needle length?
How many times do you use a syringe?
Do you split larger doses, and how much insulin before you would split?
What’s the correct procedure for giving a shot?
How do you make sure you’re giving it into fat or subcutaneous?
Do you squeeze the skin and then give it? Or not?
Do you ever get distracted and “forget” how much insulin you just took? Tips for recording or not getting distracted?
Where do you line up the plunger for the dose?
What’s with the space at the top above the first line? Sometimes it looks almost as big as a unit?

And any other tips you might have. Thanks!


I use 8mm x 31g, and will use a syringe 2 or 3 times within 12 hours.

I don’t split larger doses; the largest dose I’ve taken in one injection is 33u (by overfilling a 30u syringe) for an enormous carb meal. But I have heard that a large bolus in a single spot takes longer to completely absorb than it would if spread over, say, 3 separate spots.

I’m not going to call my procedure “correct” but what I do is draw air into the syringe equal to the number of insulin units I want, then expell the air into the vial, draw some insulin into the syringe with the needle pointing upwards in the vial and expell it back into the vial to force out any small air bubbles. Then I draw the desired dose into the syringe, and just stick it in my skin where I have a good fat layer. I don’t squeeze the skin up because I’m injecting where the fat is considerably thicker than the 8mm length of the needle. For a lean person, or if injecting where there isn’t much fat layer, pinching up the skin would enable injecting below the skin but above the meat.

I have a log book where I record set changes, sensor changes, and syringe injections: I write down the units and time immediately after using the syringe. There isn’t enought time for me to forget what I just gave.

Indeed, the space above the first line is where the first unit of insulin goes. So when filling the syringe, if the space up to the first line is filled with insulin (so the tip of the plunger is at the first line) that’s one unit of insulin in the syringe. If you fill liquid up to the second line that’s 2 units of insulin.


Thanks for all your info. I have a pretty detailed log book too. I record time and BG value, and then the amount of insulin and the time I take it, along with the food amounts and carbs that I used to figure my dose. But, if I’m not paying attention, ie talking, thinking about what I’m fixing etc when I take my shot, I sometimes wonder if I took the correct amount. I need to be more deliberate about it, hence the refresher.

So the line on the syringe that is longer and pretty clearly labeled 5, isn’t really 5 units?


Maybe some pictures will help. I used food coloring to make it easier to see. It isn’t red insulin. :grinning:




@Jan I used the 4mm needles my Endo recommended on flex pens for Novolog and Lantus, vice actual syringes and vials (viles? :sweat_smile:). I found the BD Nano 2nd Gen needles were much more comfortable than Droplet needles (only two I tried, Wegman’s only had the BDs for my first set, military pharmacy only had Droplets. I like the BDs so much, I got the doc to write the script for them only!).

I originally used 12 units of Lantus at night, but found myself going low in the early morning, so split my Lantus dose to first thing in morning and at bedtime, but had to increase it to 7 units each. Not sure it’s the best approach, but I used my thighs for Lantus, alternating sides of leg and leg for each injection, and stomach/love handles for Novolog (left side in morning to right side in evening). I’d pinch up what I thought was a layer of fat (sub-c tissue), needle roughly 90°, with the 4mm needle inserted all the way, it’s hard not to be sub-c.

Yes, I’d forget to dose early or what I’d given (even “if” I’d given a few times), but always reconstructed and logged afterwards (one of the reasons I like having the pump), but that was the first few months of dx. It’s now just part of the routine of meal prep to bolus…I still count carbs using MyNetDiary and track just about everything with Sugarmate, though I don’t analyze the data unless I note a change/out of wack BGs. I still don’t bolus early enough, perhaps with more time…or until dementia kicks in…

Not using a standard syringe, so no plunger involved. One of the easy things with pens, just dial the dose in 1/2 or full units. I don’t have clue about the line you mention…

You’ve been doing this so much longer, I feel odd giving tips, but here goes: 1. Keep your short-acting and long-acting in separate places! I, like a few others, I was tired one night, kept both types in my nightstand and gave myself 12 units of Novolog instead of Lantus…stayed up that night eating/drinking things I hadn’t had in long time. 2. If you haven’t tried a pump and ruled it out, give one a try! They release you from many injections, it’s easy to bolus, and some are covered by Medicare/Insurance (if cost has stopped you previously); the downside is there’s a lot of waste involved and you need to maintain a backup of pens/syringes/vials. 3. If you like pens, try the Novolog Echo for 1/2 unit dosing (it requires cartridges, but other than that is pretty much the same); alternately, try the InPen, it keeps track of doses/times and wireless reports to a couple of apps on phones/pads.



The line marked 5 is indeed 5 units. I agree with what Eric shows in his pictures. If you were talking about the headspace above the plunger when the plunger is pushed all the way in, that space doesn’t count because any insulin in that space can’t be delivered into your body because the plunger doesn’t go any farther. As an aside, that turned out to be important with the covid vaccines: if they used a special syringe that was designed to expell every last drop out of the headspace, they could get one extra dose out of a vial of covid vaccine.


Thanks! I was about to post a picture of what I was talking about re: the area above the first line.
Am I losing it? Or does it seem like that area above the first line on some syringes (I use BD 8 mm, 31 G) is pretty large? When I got to looking at it, it threw me for a loop. I never thought about it before. Doesn’t it look like there is at least a 1/2 a unit there?


4 mm vs 8 mm - pros and cons?

Tell me more about the pens, I don’t really know much about them and sometimes I need 1/2 unit. I don’t like the 1/2 unit labeled syringes, and I end up going back and forth with the plunger forever, before I’m satisfied that I’ve got a 1/2 unit. For my Lantus, 11 is too much but 10 isn’t quite enough.

But we could all use a refresher/reminder now and then, and learn from each other! I live in a pretty rural area, so don’t know anyone who is T1D. In fact, in the whole 43 years of being T1D, I haven’t known any T1Ds. So this forum is a blessing!

Yes! I learned this the hard way too! Novalog in the kitchen, Lantus in the bedroom (I take it at night).

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:thinking: This one I’ll have to think about. What keeps the plunger from going any farther? It sure looks like there is insulin in that headspace in @Eric 's photos. Maybe I’m just being obtuse. Or bull-headed :ox:, but I just want to understand it. :person_shrugging:


Some syringes have 1/2 unit markings also! Are you using those syringes?

If you can take a pic of your syringe and post it, that might help.


The plunger can’t push any further.

Try this analogy…
Imagine a full glass of iced tea. You take one sip from a straw. The only part you drink is what goes in your mouth. There is still some drink in the straw when you are finished with the sip, right? You did not drink that part.

So imagine the insulin left in the needle after you are done injecting. Does that go in your body? No, it stays in the needle, right? Because the plunger is not going into the needle to push it into your body.

With every syringe, there is some dead space. Insulin that can’t get pushed into your body.


When I was using those things (more than 20 years ago) I counted backwards; the first broad line is clearly labelled and there is, and never has been, a “0” even though I personally think that is pretty damned stupid. So I counted backward from 5 if I actually had to do that. At that time if I wasn’t shooting up at least 5 I was probably wasting my time.


@Jan You apparently have internet, so I recommend doing a google or YouTube search for “insulin pen” and “insulin pen half unit” to find references so you can evaluate for yourself. My experience is with only one brand. That said, here’s my commentary:

I can’t speak to pros/cons of 4 vs 8mm. I’ve only used 4s. Differences are obviously depth, potential discomfort, and potential for going IM (intramuscular) vs sub-c (I don’t think 8mm would go IM, but others here can advise with direct knowledge).

Ref pens: They exist for about every insulin type. Most are self-contained plastic throw away units with 3ml each, boxes of five (5) pens. They use screw/twist on disposable needles that seem fairly standardized connectors in various lengths/gauges and bought separately from pens; I like BDs, others like other brands, costs vary. Most are U100, but other strengths exist. Some are “smart” like Inpen and internally record/link to apps via Bluetooth for logging when and how much; InPens are good for one year, then you buy another, cost is often covered by insurance, but you can buy for $35. Some pens, like Novolog Echo, have 1/2 unit dosing (others exist, just google for 1/2 unit insulin pens). The Echo (How to use NovoPen Echo® - Quick Guide - YouTube), while a pen, uses cartridges of insulin, instead of being self contained; the exterior appears to be metal cap and body with plastic cartridge holder inside that twists off the metal pen body that holds the plunger/dosing mechanism. To avoid confusion, the InPen and Echo (probably others that take cartridges) come in colors to differentiate short and long acting insulins. Both have similar twist dialing for dose, except you dial in half units instead of full units.

If you’re using Lantus with 10/11 units once a day, splitting your dose is pretty easy. I’m no doc and you should discuss with him/her before or after as you’re comfortable with. I did it on my own, tried splitting the dose that seemed to cause early morning lows in half (instead of 12 at night, I took 6 one night at bedtime, then another 6 the next morning, my times were slightly asymmetrical, not strictly 12 hours apart). I noticed I ran a bit higher at night and between meals, so I upped the morning dose 1 unit after a couple of days; I still had the problem at night, so upped the evening dose 1 unit for a total of 14 per day. NOTE: If you do this yourself, I recommend giving yourself 2-3 days for each change to let things “settle” in and ensure it’s working/not working, alternately talk about with your doc. If it works for you, great! If it doesn’t switch back, but watch for a low that first day as you’ll have ≈50% more in your system for that first higher dose. I’ve heard from a few others having similar experiences as mine, so you could find you will need a slightly increased Lantus dose total.

I agree with learning, I’ve learned more about being/treating T1 diabetes (dosing for carbs, dosing for fat/protein, pumps, CGMs, etc.) from JuiceBox, Taming the Dragon, FUD, TCOYD, T1Exchange, etc., than I ever have in 15 minute appts at my doc or Endo (not dis’ing Dr’s, just the time our system allows them to dedicate per person and the lack of a team approach, i.e. including a CDE, dietician, DNP). And I’m still learning from all comers: old, young, long-time T1s, short-time T1s, and a bunch of non-T1 parents of T1s!


Thanks so much for all your useful info. It’s very helpful!
I know I can find info online, but nothing beats personal experience. :bowing_woman:


The right length needle for YOU depends upon where you do your injections. Generally you’re trying to get the insulin into the fat layer or the interstitial layer between skin and the muscle.
If you do them in the abdomen it’s not that critical. If you do them in the arms and you’re muscular without much body fat you probably want a shorter needle than an 8 mm and may want to pinch… I’ve been using a 6 mm 31ga. for the past 10 years. It’s an adequate length as long as I always inject carefully at right angles to the surface. As far as technique, if you go to the ADA website the materials they have for newly diagnosed persons with type one are pretty clear.


Thanks for the info, and the lead to a good resource. :clap:


There are also Youtube videos.
Here’s a good one if you want to restart as if it’s completely new to you.

If the presentation style doesnlt suit you, the suggested videos list that is on the same page has links to training videos for registeded nurses, lessons by pharmacists.

When I want to mke sure that I’m doing something following best practice, I look at multiple article of videos on thesame topic. Usually by the end of the 4th video, I’ve identified what they all have in common, and I’ll do that unless there is an explicit warning not to that makes objective sense to me.

The exception is disposal. Imo, any product made of recycleable materials that isn’t designed to be as recycleable as is safe is bad. Insulin syringes and infusion sets are two badly designed products. Hospitals can justify throwing stuff away and pay “someone else” to hande it because of cost of skilled labor and higher risk, I can’t .

If I accepted the “it’s touched biood, so it’s dangerous” line, I’d have to put my used test strips into a sharps container, not just the lancettes and syringes. Also bloody tissue used to stop a bloody nose and a blister pack if I cut mysef opening it. I don’t.

I’ve done 3-6x injections every day for too many decades. Doing what I was taught I carefully recapped the needles and the plungers and oput the whole thing into a sharps container- where they sat. (I’ve never stuck myself with a needle by accident).
For the first 10 years I had large orange sharps containers accumulating in my apartments with no place to dispose of them. The stores that sold me syringes wouldn’t take them, nor my doctors. Relatively recntly that has changed. Some doctors will add patients sharps to their own collecton boxes

(the following mght be deleted by a moderator if it violates site permission, but I have to say it anyway. )
I got past the “we donl’t accept that” by reducing the size of a years sharps by 80%. I recap the needle, break the needle and hub off the distal end of a used syringe, separate the plunger and rubber seal. Only the needle and hub and lancettes go in my sharps containers, which are red-capped Coffeemate canisters labeled with a permanent marker. I use clear plastic packaging tape to seal them when they are filled. These are small enough that they donkt take much soace and my local seniors center will accept them for later collection.

The broken syringe can’t be used for injections, isn’t sharp and is less potentially dangerous than a sharp pencil. The cartons, bags, plunger caps, plungers and syringe bodies are different types of recyclable materials and put into similar material containers for possible disposal as recycleable waste. Separation takes less than 10 seconds per syringe.

The disposal volumes dropped by 75% when I started re-using syringes when at home. The number last year was down to 365.

Officially, both these practices are strongly discouraged, but I have never been accidentally stabbed by a syringe, my re-capped sharps and lancettes are safer than intact syringes thrown into sharps containers withiut cappin. Containers of non-sharp syringe components that are labelled with my name and put into recycling have never returned to me.

It looks like I’ll have to go though a similar exercize with CGM and pump “waste-ables”.


Welcome to FUD @psfud123, your contributions are awesome for a new poster. Thank you!
As far as site permissions, we are pretty easy bunch to get along with, since we are a completely private, self managed organization that receives no money from anyone. So please, don’t try to sell us anything and share your experience and you are unlikely to run afoul of our “rules”.

The only potential issue is politics, we keep all political talk in the politics area. Other than that, feel free to contribute anything you would like. If you want to see the wilder side of some of our members do a search on Intramuscular injection technique or any number of other edge topics. Knowledge is power.