On the subject in the title: Angle of injection and whether 90 degrees is always right Working notes rather than a conclusion.
Something about angle of injection does not reconcile and I would like a second pair of eyes before I decide which half is wrong.
Two sources, both reputable, giving figures that cannot both be right unless they are measuring different quantities. My suspicion is that they are, and I cannot see how.
I had written a reply contradicting the opening post and deleted it. Here is what survived.
Leak-back after withdrawal: a small amount of liquid on the skin after withdrawal is ordinary. Whether you lost a "meaningful" dose depends on concentration and your target dose, but some leak-back is universal and does not need to be treated as an error.
If you have to inject at a different time of day than usual, that is a much smaller perturbation than it feels for a weekly compound with a week-long half-life.
Old habit: I write down the expected answer before I calculate it.
One more thing on angle of injection that took me far too long to see: the two figures people quote are not measuring the same quantity. Once you notice that, the apparent contradiction disappears.
Post #2 is right about the mechanism and I think understates the practical bit.
Summarising the angle of injection thread so far, since it is long and the answer is buried: the first reply has the method, the fourth has the correction to it, and the rest is people agreeing at length.
Coming back to post #4, because the follow-up matters more than the original answer.
A new needle for each injection is not fussiness. A needle blunts on first use and a blunted needle is the reason the second injection hurts more than the first.
The general answer and the answer for your case may diverge here.
Bleeding at the injection site: normal and usually minimal. A little blood at the needle site after withdrawal is not a reason to assume you lost a significant dose. The needle passed through tissue and there is a small amount of bleeding in the tract.
That is consistent with mine, for whatever one more account is worth.
If you have to inject at a different time of day than usual, that is a much smaller perturbation than it feels for a weekly compound with a week-long half-life.
That is the version I would defend. It is not the version I started with.
On post #12 — agreed on the reasoning, with one qualification.
Offering a way to settle angle of injection rather than another opinion about it. Two measurements, taken the same way, a fortnight apart. If the difference is within the noise, the question was not answerable at this precision.
Cold solution and stinging: warming the vial in your hands for a minute before injection reduces the stinging sensation substantially. This is the simplest thing to try if injections are uncomfortable.
A guess, clearly labelled as one.
Thank you for taking the time. That was more work than a reply usually is.
Angle of injection: 90 degrees into pinched tissue ensures subcutaneous placement. It is not always necessary and shallower angles can work, but 90 degrees into a small pinch is the safest technique to learn first.
Narrowing post #19, because the general version has more than one answer.
I have three months of notes on angle of injection and the honest summary is that the trend is real and the week-to-week numbers are noise. I nearly drew the opposite conclusion from the first fortnight.
Post #20 answers the question as asked. The question underneath it is different.
Air bubbles in a subcutaneous injection: the honest risk assessment is low. Tiny air bubbles in subcutaneous tissue do not behave like an air embolism in a blood vessel. A few air bubbles are not a reason to restart the entire injection.
Somebody will have a better source than mine, and I hope they post it.
I read post #19 twice before replying, because I had assumed the opposite.
Injection discomfort: comes from needle gauge (finer = less discomfort), volume (smaller = less discomfort), temperature (room temperature or warmed is less uncomfortable than cold), and technique (smooth, purposeful injection is less uncomfortable than hesitant). All four are under your control.
It is worth stating the boring hypothesis before the interesting one.
Drawing up with one needle and injecting with another: a reasonable practice if you have extra needles. Fresh needle for injection reduces tissue drag and can decrease discomfort. Not necessary, but not harmful either.
Post #24 is right about the mechanism and I think understates the practical bit.
If you have to inject at a different time of day than usual, that is a much smaller perturbation than it feels for a weekly compound with a week-long half-life.
Not the answer, but possibly the question that gets there.
Subcutaneous injection into abdominal tissue, thigh or upper arm is what the licensed labelling in this class describes, and the published comparisons found the differences in exposure between those sites small.
I have kept the units in throughout, for the obvious reason.
Pinch or no pinch: the decision depends on needle length and on your own anatomy. A longer needle (8 mm and up) reaches subcutaneous tissue easily without a pinch. A shorter needle (4-6 mm) is safer with a gentle pinch. The pinch size matters less than people think; the injection angle matters more.
On post #26 — agreed on the reasoning, with one qualification.
Pinching a fold is useful for lean tissue and unnecessary elsewhere. The point is to keep the needle out of muscle, and whether you need to depends on the site and on you.
It is one reading of the data and not the only reasonable one.
Marking my uncertainty on angle of injection explicitly. I am confident about the direction, much less confident about the size, and not confident at all that it generalises past the case in the first post.
If someone has run angle of injection properly I would rather read that than my own reconstruction of it. Posting mine only because the thread has gone quiet.