mcg vs mg vs IU
Peptide labels and research papers mix several units. Here is how they relate.
Weight: mcg and mg
1 mg (milligram) is 1000 mcg (micrograms). A 5 mg vial holds 5000 mcg.
Volume: mL and units
Millilitres measure liquid. On a U-100 insulin syringe, 100 units is 1 mL, so 1 unit is 0.01 mL.
Turning weight into volume
You need the concentration: vial mg divided by water mL. 5 mg in 2 mL is 2.5 mg/mL, so 250 mcg is 0.1 mL, or 10 units.
IU
International units measure biological activity. They are used for compounds like HGH (somatropin), where 1 mg is commonly given as about 3 IU. IU does not convert the same way for other peptides.