How this instrument works
Morphine milligram equivalents, MME, translate a daily opioid dose into the dose of oral morphine that would produce roughly the same effect. Every opioid gets a conversion factor benchmarked against morphine: oxycodone at 1.5, hydrocodone at 1.0, hydromorphone at 4.0, oxymorphone at 3.0, codeine at 0.15. Multiply the daily milligrams of whichever drug is prescribed by its factor and the result lands on the same axis as every other opioid a clinician might compare it against.
The factors themselves come from the CDC, published alongside its Clinical Practice Guideline for Prescribing Opioids for Pain and carried forward, largely unchanged, from the original 2016 guideline through the 2022 update. Pharmacy systems, insurers, and prescription drug monitoring programs all lean on the same table, which is exactly the point — a chart written in oxycodone milligrams and one written in hydromorphone milligrams become directly comparable the moment both are converted to MME.
Cumulative MME per day is also used as a rough flag for risk. The CDC guideline notes that overdose risk climbs measurably at higher cumulative doses, and it calls out roughly 50 and 90 MME per day as thresholds where extra caution and closer review are warranted — not hard ceilings, but points where a second look at the regimen makes sense.
- Choose the opioid from the Drug menu — each option carries its own fixed conversion factor.
- Enter the Total daily dose in milligrams, summed across every dose taken in a day.
- Read MME/day; the working block shows the multiplication in full.
- Re-run the figure whenever a dose or drug changes — MME is a snapshot of the current regimen, not a running total.
Worked example — 30 mg/day of oxycodone
A patient takes 30 mg of oxycodone daily, split across several doses. Oxycodone's conversion factor is 1.5, so 30 × 1.5 = 45 MME per day.
Switch the same arithmetic to a stronger drug and the gap shows up fast: 8 mg per day of hydromorphone, factor 4.0, also works out to 32 MME per day — nearly as much risk-equivalent exposure from a quarter of the milligrams, because hydromorphone is that much more potent gram for gram. At the weaker end, 120 mg per day of codeine, factor 0.15, comes to only 18 MME per day, despite being the largest number of milligrams of the three.
Questions
Can I use MME to switch a patient directly from one opioid to another?
No, and this is the single most important limitation of the tool. MME conversion factors are population averages built for surveillance and risk flagging, not individualized recipes for opioid rotation. Real people vary in genetics, tolerance, drug interactions, and incomplete cross-tolerance when moving between drugs — the same calculated MME can be more or less potent from one person to the next. Switching opioids safely requires a qualified clinician, a deliberate reduction from the calculated equivalent dose (rather than a milligram-for-milligram swap), and close monitoring, because equianalgesic tables are approximations and naive conversion carries a real overdose risk.
Why do MME thresholds like 50 or 90 matter?
The CDC's guideline cites cumulative doses above roughly 50 and 90 MME per day as points where overdose risk rises enough to warrant extra caution — closer monitoring, a documented reason for the dose, or consideration of naloxone co-prescribing. These are review triggers for clinicians and prescription monitoring programs, not fixed limits that make a dose unsafe below the line or automatically safe above it.
Where do the conversion factors come from?
From the CDC, first published with its 2016 opioid prescribing guideline and carried forward without change through the 2022 update (MMWR Recomm Rep. 2022;71(3):1-95). They were derived from pharmacologic potency data and expert consensus, benchmarked so that 1 mg of oral morphine equals 1 MME.
Does MME account for tolerance or how long someone has taken opioids?
No. The calculation only multiplies a dose by a fixed factor — it has no memory of how long a person has been on therapy or how their body has adapted. Two patients on identical MME figures can have very different real-world risk depending on how long they have been stable at that dose versus just starting it.
Is a higher MME always more dangerous?
Generally, yes, in the aggregate — population studies show overdose risk trending upward with cumulative MME. But it is a statistical association, not a certainty for any one patient, and factors like concurrent benzodiazepine use, sleep apnea, and renal or hepatic function matter alongside the raw number.
Why does hydromorphone have such a high conversion factor?
Because it is roughly four times more potent than morphine milligram for milligram — a much smaller dose produces a comparable analgesic and respiratory-depressant effect. The factor of 4.0 reflects that pharmacologic strength, not anything about how the drug is dosed in practice.
References
- CDC Clinical Practice Guideline for Prescribing Opioids for Pain — United States, 2022 (MMWR Recomm Rep. 2022;71(3):1-95)
- CDC — Calculating Total Daily Dose of Opioids for Safer Dosage (conversion factor table)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.