relative potencies of morphine via various routes

Last reviewed 09/2021

The relative potency of morphine when given by various routes is given below:

Route Potency relative to oral morphine
oral morphine 1
rectal morphine 1
subcutaneous morphine 2
intravenous morphine 3
subcutaneous diamorphine 3

i.e. 3mg oral morphine is equivalent to 1mg of subcutaneous diamorphine

Check summary of product characteristics before prescribing any drugs mentioned.


  1. West Midlands Palliative Care Physicians (2003). Palliative care - guidelines for the use of drugs in symptom control.