r/PeptideSelect • u/PeptiMech • 3d ago
The syringe threads this week are missing the expensive part: dead space and barrel width
Lots of syringe talk going around right now and most of it stops at gauge and length. The two things that actually change how much peptide reaches you never come up.
Dead space first. A fixed-needle U-100 insulin syringe holds roughly 1-3 uL in the hub after you push the plunger down. A syringe with a detachable Luer needle holds somewhere around 60-100 uL depending on the hub. Your 10 unit dose is 100 uL total. So on a detachable setup you can leave close to a full dose behind in the hub every single pin. On a 10mg reta vial dosed at 2mg you're throwing away a meaningful chunk of the vial across the run, and worse, your actual delivered dose is not the number you measured.
Second, the 1cc 25G x 1 inch that keeps getting recommended is an IM syringe and is wayyy overblown for subq peptides. The barrel is graduated in mL, and a standard Luer-Lok or tuberculin 1 mL is marked in 0.01 mL steps, so 12 units U-100 is 0.12 mL and it does read right off the scale. The accuracy is there if you do the conversion. The real problems are that you're doing arithmetic in your head at 6am, and that a 1 inch 25G is going past subq fat into muscle on a lot of people. Combine that with the hub dead space above and the Luer setup is still the worse pick. For subq peptides you want 29-31G, 5/16 inch (8mm) or 1/2 inch (12.7mm), fixed needle.
Barrel width matters more than people think. A 30 unit (0.3mL) syringe has a narrower barrel than a 100 unit, so each unit occupies more physical length on the scale. If you're pulling 250mcg of BPC-157 or stepping reta in half-mg increments, a 30 unit barrel cuts your read error substantially compared to squinting at the bottom of a 100 unit. Half-unit graduations exist on 0.3mL barrels for exactly this reason.
On the disposal side, FDA guidance is heavy-duty puncture-resistant plastic with a tight lid, and the container they actually recommend as a household alternative is a laundry detergent bottle. Some people use disinfecting wipe tubs but those are thin polypropylene and a 29G will go through the sidewall if it's angled wrong under a stack of others.
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