Reverse BAC

‘Reverse BAC’ is community shorthand for reconstituting a peptide in less bacteriostatic water than a standard reconstitution chart would suggest, in order to produce a more concentrated final solution. The motivation is usually one of two things: smaller injection volumes (which sting less and are easier to draw accurately on a 0.3 mL U-100 syringe), or extending the usable life of a vial by drawing smaller volumes.

The trade-off is dose precision. A higher concentration means each unit on the U-100 syringe corresponds to more micrograms of peptide, which amplifies the impact of small volumetric errors. For low-dose peptides (ipamorelin at 200 mcg, BPC-157 at 250 mcg), this is usually acceptable; for compounds where dose-response is steep, reverse-BAC reconstitution is questionable.

Always run the reconstitution math through a calculator before adopting a reverse-BAC ratio. Eyeballing the conversion is a common source of dose errors.