Well, a needle is a technology, too

Is there any logic to the fact that doctors, nurses, etc. prescribe (for use with insulin pens, Ozempic pens, etc.) long needles, e.g., 8 mm, for fat people to give themselves subcutaneous injections, usually in the abdomen.

One of the kids is a young OB/GYN, has cut up a few human beings - all of whom are still alive, as far as I know - and he says that

  1. he has never seen a skin layer over the subcutaneous fat more than 3 or 4 mm thick, and
  2. he has never seen a correlation between obesity or any other body habitus and the thickness of the skin over the subcutaneous fat.

Will someone please tell me what’s going on?

I really have a practical reason for wanting to know this.


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I don’t know how it works for others, especially people in the US, but my doctor gives me a prescription for “pen needles” and I decide the rest (type, length) based on personal preference. I prefer the 8 mm needles because I find the 4 mm ones really sting.

I would think that rather than longer needles being recommended for people who are overweight, it would make more sense to recommend shorter needles for people who are skinny so that they don’t accidentally go too deep.

I believe 8 mm is slightly less than 3/8 inch which is the length of the needles Included with the syringes I used and had no issue with them.

My aunt was obese and when she passed I took her 1/2 inch syringe needles and had no issue with them either. I was more concerned with the gauge - preferred 31 g needles. 29 g needles were tolerable but definitely could feel the pinch.

this is a really critical topic!
I’ve been a type 1 for over 15 years with excellent diabetes management (5,8-6,0 HbA1C) but last year started having enourmous problems with controlling my sugar levels. High doses of insulin did not work and sudden drops with limited or almost no insulin injection started. I lost consciousness for the first time in my life. Nothing made sense. We started monitoring the situation with a great medical team of endocrynologists and diabetologists who all got direct access via cloud to my libre system. We followed with extensive tests in a strict controlled environment of a university hospital to figure out what the hell was going on. I have never been tested so much in my life (i guess i was an interesting test subject). we all went through enourmous amount of literature in english, french and italian and literally started testing for diseases which occur in 1 to 30 mln people to find some sort of explanation (weird lung tumors, insulinomas, etc). It seemed like a ‘dr house’ type of situation.
After crossing all of them out we have returned to square one. The insulin was ok, the equipment was ok, I was ok (by all measurable medical standards), so what the hell was wrong? The last thing we started checking was the skin/tissue and injection sites.

We were all quite smart about diabetes (uni hospital full of professors and experts in the fiedl), I have never seen a difference in absorption rates depending on an particular body zone injection site or needle lenght, i am fairly slim and have a hardly detectable lypohypertrophy. But yet - the needles, injection sites and that limited lypo proved to be the source of all problems. Once we changed the needles and injection sites - all returned to normall.

Really little attention is given to injection sites control, needle length/reuse and injection technique. Maybe beacuse this is a slowly growing problem which doesn’t manifest immediately. It also isn’t anybody’s exact domain - this area lies somewhere inbetween the key knowledge of a nurse, a diabetologist, a physiosterapist and dermatologist. And let me be clear - this issue can absolutely destroy your feeling of self confidence in diabetes control.

If you are still injecting with 8mm needle (i did for many years) please go to fit4diabetes.com. This is a great initiative which based on scientific data explains in detail how to inject insulin, what type of needles to use and how to avoid unfortunate consequences of doing it wrong. And 8mm needle or longer - it is a mistake!

Some useful shortcuts:


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Thanks a lot, @Matt; the first pdf you posted is certainly relevant and certainly useful. (I haven’t read the others yet.)

My only problem with the pdfs is their ultimate source. When you manage to squeeze down to the fine print, it turns out that the world-scale philanthropists and saints who run http://www.fit4diabetes.com/ and who distribute those pdfs are none other than… Becton, Dickinson UK Limited. I don’t see how they would make any significant profit from lying on this subject, but I happen to have some inside information about SOME (direct-to-doctor) advertising by SOME giant pharmaceutical companies, and as far as I can see the horror stories are at least sometimes true.

I don’t trust pharma advertising, and I suppose that I will be driven to doing a bunch of searches on the new spiffed up PubMed. In the meantime, I suppose I will provisionally treat the no-need-for-long-needles position as being true for my purposes.

Thanks a lot.

Nicely noticed! Well they sell needles so the more needles we use… absolutely understand the level of distrust. Big pharma are profit driven corporations and trusting them to advertise accordingly, advance breakthroughs and cure diseases (especially such as diabetes which guarantee high spending customers for life) is like believing oil companies’ ultimate goal is to quickly transition the world to renouvable energy sources;)
Regardless of who the donors/distributors are I recommended the site because Ive done some research on my own and what they presented seemed not only scientifically valid but also straightforward and comprehensive.

There aren’t many sites / articles discussing this issue comprehensively. If you find some additional material - please share.

Cheers, M.

I took a quick stroll through PubMed to see what I might find on the subject. I found exactly one article that was exactly spot-on. I’ve downloaded a copy of the full article (oodles of money or some kind of subscription access required), but if I understand correctly I can’t post it here because of copyright laws. However, think I can post some short excerpts here without the slightest problem, and send you the whole article if you like.

First, the ‘cite’:

Naushira Pandya, Nancy Losben, Jane Moore, “Optimizing insulin delivery for patients with diabetes”,
Geriatric Nursing, Volume 39, Issue 2, 2018, Pages 138-142,
ISSN 0197-4572, https://doi.org/10.1016/j.gerinurse.2017.11.007.
From p. 140, more or less:

  1. The safest pen needle is the 4 mm one, which is suitable for
    adults and children, regardless of age, sex, ethnicity or BMI, and
    it should be inserted perpendicular to the skin surface, whether
    or not a skinfold is raised. A 5 mm pen needle is also accept-
    able for obese patients. Injecting perpendicular to the skin
    represents a shift from older guidelines which recommended in-
    jecting at a 45-degree angle.28
  2. The safest currently available syringe needle is the 6 mm one,
    but when this is used either in children, in extremely thin adults,
    or into the arm, a skinfold should be raised because of the ex-
    cessively high risk of intramuscular injections.
  3. To minimize the risk of needle stick injury (NSI) through a
    skinfold, it is recommended that 4 mm and 5 mm pen needles,
    and 6 mm syringe needles, be used without a raised skinfold.
  4. Patients… should never inject into sites
    of lipohypertrophy, inflammation, edema, ulceration or infec-
    tion, or through clothing.
  5. Patients should be trained in proper site rotation and use of larger
    injection zones, as a primary measure to avoid development of
    lipohypertrophic lesions, and as a secondary measure to mini-
    mize worsening of existing lesions.
  6. Pens should never be shared, since they are no longer sterile after
    a use.29 Prior to injection they should be primed, completely in-
    serted, and care taken to hold down the thumb button for a full
    10 seconds, and pressure on the button maintained until the
    needle is completely removed, to prevent insulin leakage and
    to prevent the patient from pulling the pen away before a full
    dose is received.
  7. Syringe needles should also be used only once. Unlike pens, the
    needle does not need to be left under the skin for a count of 10.
  8. Patients should receive specific instruction and practice in choos-
    ing sites for injection, particularly in avoiding sites of
    lipohypertrophy (LH) and in site rotation. Additionally, sites
    should be examined for LH at least once a year, or more fre-
    quently if LH is already present.
  9. Safety injection devices should be considered first-line choice
    if injections are given by a third party. Pens and syringes with
    needles used in this setting should have protective mecha-
    nisms for all sharp ends of the delivery device.

To get back to our point, from what I understand from the rest of the article, 4mm needles should be fine for any patients, just as said surgeon told me. (The 3 or 4 mm skin thickness is my typo; it should be 1 or 2.) Noone on earth needs longer than 5 mm.