Fat allows for better absorption of peptides, it's slower and more effective.
From what I remember reading about one attempt at intramuscular administration you'll get rushing nausea at almost any dose, often followed by vomiting. There were no noticeable tanning effects.
I wouldn't even consider an IV injection, and advise anyone else not to either.
If you're struggling for fat I'd advise reading up on Google about 'low body fat subcutaneous injections'.
There should be a couple of good suggestions and information on short needles and injecting at an angle. While all bodies are pretty similar the last little bits of fat can vary so it's a good idea to have a look though, there may be somewhere you hadn't though of.
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I'm only at around 12% bodyfat but it feels like when i pinch fat at my lower belly i'm only pinching skin. Maybe i am still injecting into fat?
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At 12%, you've got nothing to worry about. When a skinfold is like that on the back of your hand, THAT's when you have no body fat. ]
You can also inject into fatty skinfolds in other places - eg the love-handles, buttocks, upper legs, etc. Arguably different sites have different absorption rates, but I've never noticed any significant difference in practice.
And if you really run out of fat, you can pin into the muscle - just aspirate to make sure it's not into a vein. SubQ injections are certainly the recommended option, but on the occasion I've pinned intra-muscularly, I've not experienced any ill effects.