4 mm needles

I just went to pick up some pen needles because I'm running out of the ones that I use for backup (noticed today when I went to do a shot because my BG was 25 / 450 after lunch).

The pharmacist gave me a pack of five needles that are 4 mm. I asked if they had longer ones; the ones I've used in the past (and I haven't needed new ones in something like five years) are 8 mm. Another pharmacy staff member came over and said that I didn't need longer, the 4 mm were the latest and greatest and would work fine. I asked if insulin would leak out of the injection site and she said no.

I only ever use pen needles when my BG is extremely high and really would prefer 8 mm needles so that I'm sure I'm getting the insulin when I do a shot. Does anyone use 4 mm needles, especially if they are overweight? I'm going back tomorrow once I make sure these ones fit my pen, but she's going to be very reluctant to give me 8 mm ones as she's SO convinced that 4 mm ones are better and are thinner and painless. I don't care about pain - though I don't find the 8 mm ones hurt - but I do care about whether my insulin dose when my BG is super high is going to absorb versus leak back out ...

I’ve read some research that has shown that the dermis or skin is the same thickness no matter how obese or thin an individual is (and it’s very thin) so a 4 mm needle will get the injection into the fatty tissue in an obese person but also minimize the risk of hitting muscle in a thin person who has very little sub q tissue for injections.

The BD website has links to research articles and a video I believe. A lot of the research is sponsored by needle manufacturers though.


I’ve always found leak back to be more related to haste and not waiting long enough after injecting before pulling out the needle with either pens or syringe vs needle length.

Thanks fro your comment. That's what the pharmacist said regarding the skin layer being the same thickness no matter what a person weights. I just wonder about people's actual experiences, if anyone has used this needle length.

I’ve only used the 4 mm needles for two or three years now although it’s been a while since I’ve needed a backup shot or was on Victoza. I don’t remember having any problems with the 4mm needles. I don’t remember personally seeing a whole lot of advantages to them either over the longer needles. Although my endo usually has a ton of samples so it’s great for backups for pump failures.


All you have to do in to be sure the needle goes through your skin to the subcutaneous fatty layer. When I realized that this was what was meant by a 'subcutaneous injection', my main thought was that it should be called an 'intradipose injection'.

If you have enough adipose tissue for an 8mm needle, you'll do fine with 4mm. No need to pinch or inject slantwise, just poke at 90 degrees. To convince yourself it's going in, just inspect the injection site right after.

While nowhere close to 'buff', I am now (after D) skinny enough as to not have acres of injection sites. 5mm ('micro', was it?) worked fine, but I like 4mm ('nano') better and returned a box of 8mm ('short') dispensed in error. 8mm would really contract my injection real estate.


hi jen, i havent used 4mm but 5 and 8mm. i havent noticed a difference at all in absorption.

I'm not overweight but the 4mm ones are great. I've used 5mm and 8mm as well and I found the 4mm to best. No leakage, no pain, nothing really bad about it and no need to pinch like with the 8mm. Insulin works the same with all of them though I think as I've not had issues with any of them? the 8mm was a bit uncomfortable though as I have only a little bit of body fat to work with and the one area is hard to do with a pinch (butt) and my tummy has very little to pinch but it works if I have to.

I am pretty new to insulin, but not diabetes. I have the Lantus SoloStar pen and it's needle is 4mm. It works just fine for me and as a needle phobe it's a good idea, one that is longer would creep me out!

It doesn't leak and certainly gets the insulin into my belly.

Give it a try, you may find you like it!

Thanks for the feedback. I will give them a try. I think the reason I am so hesitant is that I tried the shorter sized infusion sets and found they caused lots of leaking and irritation compared to the longer sized ones. Hopefully the injections from needles will be different. :)

I tried the 4mm needles and went back to 8mm. I inject through my clothes and I found I didn't always get proper depth. And I also found that even when injecting directly I had more frequent leakage. And the final point is that when I correct, I do intramuscular injections, I actually want to inject into muscle. So I go right into my quadriceps or my lower buttox.

Hmm, good point about the clothes! I don't inject through clothing too often now that I'm on a pump, but I used to all the time on MDI. And if I'm away at camp and need to inject, I might end up doing so through clothing if others are around. Although I'm sure the pharmacist would be horrified if I told her this was why I wanted the longer needles ... lol.

Jen, when I was doing MDI I started with 8's and moved to the 4's after about 3 weeks. Everything said about how and why they are better was true for me (less painful, no pinching up necessary, etc.), and they worked very well.

Even in my -- ahem! -- thicker areas. Like you, I occasionally use a pen in addition to my pump when BG is just being wonky. I love how quick they are... Install needle, dial, poke, inject, done. Not having to two-hand it with a pinch makes a bigger convenience difference than you might think.

I'm afraid to inject through clothing

It was quite a leap for me to stop sterilizing the site each time with an alc pad, and then move on to reusing a needle a few times. I was so OCD about this stuff when I first started insulin, then heard from the veterans here, and relaxed a bit.

Not there yet with punching that needle right through clothing that's been exposed to all the contaminants and bacteria floating around in the air and on every surface. You're still here and fine, Brian, so I'm just paranoid.

Although I'm sure the pharmacist would be horrified if I told her this was why I wanted the longer needles ... lol

I'm constantly amused by the "fake world" that the vast majority of the health care industry lives in vis a vis Diabetes and the "real world" all of us actual diabetics live in.

You know, the one where an a1c of 5.5 is really great and something to strive for, where lancets are reused again and again (and again), fingers are licked clean after a BG test, insulin injected through clothing, and on and on.

Golly, how much better might D care be if our care providers inhabited the same universe we do? Not necessarily being a diabetic, but at least having a "realism" address in the same universe we live in?

My wife doesn't like my injecting through my clothes. She thinks it ruins them by putting holes in them and that it leaves blood spots. Blood spots happen and the needles are too small to actually damage anything but the finest fabrics (I don't wear fine fabrics). My wife actually went with me to an endo appointment and told my endo about my "bad habit." She then asked my endo to tell me not to inject through my clothes. My endo turned to me, winked and said "tsk, tsk don't inject through your clothes."

I still do it, if I ever see evidence that it is bad I'll stop.

I didn't pinch even with 8 mm needles. I don't think I've done that since I was a kid and the needles were 12 mm and a lower gauge (so thicker).

Oh, no worries, Brian! My paranoia is... paranoia :-)

Yeah, you can get away with that if you're inject into a "well-insulated" :-) area. I could inject no-pinch on my love-handles with the 8's. However, the 4's opened up leaner areas that were too much of a (metaphorical) pain to use because of the two-handed-mombo required to get there.

Almost nothing to lose if you can get a handful of needles to try out. I don't 5 will be enough to really get an idea, but a few days worth would probably be enough to make a determination.

Oh, and those old low-gauge needles? I'm soooooo glad I never had to use those. I've heard they were rather painful much of the time.

My syringes are 8mm, my pen needles are 4mm. I usually find the syringes less painful for some reason, but not always. Not sure what is going on there. I didn't realize there are 4mm syringe needles but like you I don't use them much- only at the end of my pens usually so I will use the 8mm needles up before trying those maybe. I often angle the syringe to a diagonal if injecting into my stomach area due to less fat etc. there so I don't hit the muscle, I'm not sure if that is necessary or not there, sometimes it feels like I hit a muscle with either needle in my legs or stomach, but I'm not sure if that's the case.

I have injected through clothes once or twice but I don't like it due to not being able to see where exactly I'm injecting and what is going on and worrying about blood stains if I bleed a bit. I don't worry about damaging clothing if the material is thicker.

Ha, I ended up getting 8 mm ones. The pharmacist tired to convince me that the 4 mm were what was recommended now, but I've used 8 mm for years and they work, so I didn't feel like changing. Plus, I do want the flexibility to inject through clothing if I need to (didn't tell her that, though!).