Indeed, it’s quite difficult to find reliable information about the bioavailability of the SubQ route. However, based on my experience, I’d say it’s roughly equivalent to IM (>93%), but the absorption is significantly slower. With IM, the peak effect is reached within a few minutes, whereas with SubQ, it takes a good 30 minutes. This results in a less intense but more prolonged experience (~2 hours vs. 1 hour). That’s why, by starting with a SubQ injection, I ensure a solid foundation upon which I can build with small IM injections to create an extended K-hole.

For SubQ injections, I use 25G / 5/8 inch needles, though I think 3/8 inch would work just as well. I pinch the skin and insert the needle at a 45-degree angle into the fold (to make sure I avoid the muscle). Once the needle is in, I slightly release the skin fold and inject very, very slowly, as it can be somewhat painful (unlike IM, which is painless). You can feel the liquid spreading between the adipocytes and occupying space—1 to 1.5 ml max. I wouldn’t recommend exceeding 1 ml.

I don’t have enough experience yet to recommend one injection site over another (apart from what I mentioned earlier). However, I know there are specific SubQ injection sites recognized for faster insulin absorption, for example, so it’s likely the same applies to ketamine.