In the context of HRT, there is little to no difference between intramuscular and subcutaneous injections. Subcutaneous injections are absorbed more slowly than intramuscular injections, however this is generally not significant enough of a difference to impact dosing. It should also be noted that an injection is rarely deposited fully in muscle or fully in the subcutaneous layer which blurs any difference together even further on an injection-by-injection basis.
As a side note, pharmaceutical sources for estradiol vials typically say they are for intramuscular injections only because that is what they are technically approved for. It does not matter though.
+As a side note, pharmaceutical sources for estradiol vials typically say they are for intramuscular injections only because that is what they are technically approved for, but there is not an inherent difference. The vial contents are often identical regardless, and vial contents are ultimately what matter. Keep reading.
Source code available here on GitHub.
Full Compilation Datetime: Sat Jan 10 15:35:08 2026
+Full Compilation Datetime: Sat Jan 10 15:47:28 2026
(There aren’t LaTeXML bindings for datetime2, hanging, or hyphenat, so the formatting is slightly ugly. If you’d really like to help me out, please write those bindings!!!)
@@ -2840,7 +2840,7 @@