Oral Hydromorphone to Morphine Conversion
A 2 mg oral hydromorphone tablet is equivalent to approximately 8-10 mg of oral morphine.
Conversion Ratio
Based on the most authoritative guideline evidence, the oral hydromorphone to oral morphine conversion ratio is 1:4 1. This means:
- 2 mg oral hydromorphone = 8 mg oral morphine
The 2025 NCCN Cancer Pain Guidelines explicitly state that 7.5 mg oral hydromorphone equals 30 mg oral morphine 1, which calculates to a 1:4 ratio. This is further supported by their equianalgesic table showing this consistent conversion factor.
Alternative Conversion Ratios in Guidelines
There is some variability in published conversion ratios:
- CDC 2022 Guidelines: Use a conversion factor of 5.0 2, meaning 2 mg oral hydromorphone = 10 mg oral morphine
- CDC 2016 Guidelines: Also used a conversion factor of 4 3, consistent with NCCN
The most recent high-quality guideline (NCCN 2025) supports the 1:4 ratio, making 8 mg of oral morphine the most evidence-based equivalent.
Important Clinical Caveats
When converting between opioids in practice, you must reduce the calculated equianalgesic dose by 25-50% to account for incomplete cross-tolerance 1, 4. This safety measure prevents overdose due to individual variability in opioid pharmacokinetics and the phenomenon of incomplete cross-tolerance between different opioid molecules.
For example, if converting a patient from 2 mg oral hydromorphone to oral morphine:
- Calculate equianalgesic dose: 8 mg morphine
- Reduce by 25-50%: Start with 4-6 mg morphine
- Titrate upward based on response
The conversion factor range (4-5) reflects real-world variability in opioid response between individuals. Using the lower conversion factor (1:4) provides a more conservative approach that prioritizes patient safety.