Topic summary

A ten-fold dose error caught before injection

Devices › Syringes & needles needle gauge & length worked example syringe units dead volume Closed

This is a generated summary. It shows the 9 most-liked posts from a topic of 104, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

RidgewayTL3Regular26 Feb 2025#4

cohort_notes, post #2: Thank you for the correction. I have edited my earlier post with a note rather than silently, so the thread still makes sense to read. The error was mine and it was the kind that comes from remembering a figure instead of looking it up. Go to post

post #3 is right about the mechanism and I think understates the practical bit.

Reading units correctly: look at the marking from the side, not from above or below. The bottom of the plunger tip is the reading. Parallax error (wrong angle) is a source of dosing error.

31 likes in reply to #2 17mo

c.grimaldiTL2 Moderator31 Mar 2025#15

n.nyberg, post #12: Two things before anyone answers the substance. First, the context in the first post is clear and specific. Second, the question is framed so that an answer can actually address it. Both are the norm here and both matter more than they sound. Go to post

Picking up post #12: that is the part I would want checked first.

For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use.

28 likes in reply to #12 16mo

DOdendaalTL3Regular15 Apr 2025#21

c.grimaldi, post #15: Picking up post #12: that is the part I would want checked first. For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use. Go to post

I read post #19 twice before replying, because I had assumed the opposite.

Needle gauge: smaller numbers (30G) are finer and less painful. Larger numbers (25G) are courser. For subcutaneous injection, 27-30G is typical. Finer needles take longer to draw up but hurt less.

30 likes in reply to #15 15mo

d.tammTL2 Moderator12 Jun 2025#48

This follows post #45 rather than contradicting it.

Fixed versus detachable needles: insulin syringes usually have fixed needles (no dead volume loss to the hub). Luer-lock syringes use detachable needles (more dead volume). Fixed needles are preferred for small doses.

30 likes 14mo

a.novakTL2 Moderator14 Jun 2025#49

s.antonsen, post #33: For anyone arriving from a search: the marked solution above is the direct answer, and the replies underneath it add the caveats that make it safe to use. Go to post

On post #45 — agreed on the reasoning, with one qualification.

Needle length: typical lengths for subcutaneous injection are 4-6 mm (short), 8 mm (standard), or 10-12 mm (longer). Longer needles are needed for deeper tissue or if you have abdominal adiposity.

29 likes in reply to #33 13mo

impurity_tableTL3Analytical chemist28 Jun 2025#56

Dead volume: residual liquid in the hub and needle after withdrawal. Typical residual is 0.01 to 0.02 mL for an insulin syringe with a fixed needle. Accounting for it matters if precision matters.

32 likes 13mo

p.iyer_pharmdTL3Pharmacist7 Jul 2025#61

f.demir, post #52: Sharps disposal: needles and syringes should be disposed in a sharps container (a rigid, puncture-resistant container). Do not put them in regular trash. Many pharmacies accept filled sharps containers. Go to post

Coming back to post #59, because the follow-up matters more than the original answer.

Sharps disposal: needles and syringes should be disposed in a sharps container (a rigid, puncture-resistant container). Do not put them in regular trash. Many pharmacies accept filled sharps containers.

32 likes in reply to #52 13mo

batchlogTL3Regular8 Sep 2025#96

Syringe barrel size: common sizes are 0.3 mL, 0.5 mL, and 1.0 mL. Smaller barrels are more legible for small doses. Larger barrels hold larger volumes. Choose based on your dose.

29 likes 11mo

j.castellanosTL2 Moderator21 Sep 2025#104

b.fonseca, post #47: Reading units correctly: look at the marking from the side, not from above or below. The bottom of the plunger tip is the reading. Parallax error (wrong angle) is a source of dosing error. Go to post

Worth separating two things that post #100 runs together.

Needle gauge: smaller numbers (30G) are finer and less painful. Larger numbers (25G) are courser. For subcutaneous injection, 27-30G is typical. Finer needles take longer to draw up but hurt less.

32 likes in reply to #47 10mo

Read the full topic (104 posts)

This topic was referenced in

About the Syringes & needles categoryDevices › Syringes & needles · 4 replies
Dead volume across syringe and needle combinationsDevices › Syringes & needles · 80 replies
Reading U-100 graduations, with a conversion table — what changed sinceDevices › Syringes & needles · 2 replies

This topic was closed 90 days after the last reply. Closing is automatic for quiet topics so that a settled answer does not collect new questions underneath it. If you have a follow-up, open a new topic and link back to this one — that keeps both readable and gives your question its own title.

Moved from Cold chain by t.vasquez. Category placement is not obvious from outside and getting it wrong is expected. This topic will get better answers here. The move is recorded in the public log citing R7.

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