How this instrument works
Hydroxychloroquine is taken long-term for conditions like systemic lupus erythematosus and rheumatoid arthritis, and its main dose-limiting concern is hydroxychloroquine retinopathy — progressive, and potentially irreversible, damage to the retina. Risk rises with both the daily dose relative to body weight and the cumulative duration of treatment, which is why prescribers work from a weight-based daily maximum rather than a single fixed dose for everyone.
In 2016, the American Academy of Ophthalmology (Marmor et al.) revised its screening and dosing guidance, lowering the recommended maximum from the older, commonly cited figure of roughly 6.5 mg/kg calculated against ideal body weight, to 5.0 mg/kg/day calculated against actual (real) body weight. Both parts of that change — the lower multiplier and the switch from ideal to real body weight — were made because dosing by actual weight was found to correlate better with observed retinopathy risk than dosing by ideal weight. Following the revised ceiling was associated with keeping the 5-year risk of retinopathy under about 1% and the 10-year risk under about 2% in the data the guideline reviewed.
This calculator performs only the mg/kg arithmetic. It doesn't know the condition being treated, kidney or liver function, concurrent medications such as tamoxifen, pre-existing retinal disease, or other factors that can raise individual risk — all of which the prescribing clinician weighs. Prescribed doses are also commonly rounded to available tablet strengths and may be set lower than the calculated maximum at the clinician's discretion.
- Enter the patient's actual (real) body weight in kilograms — not ideal body weight.
- The calculator applies the current ceiling of 5.0 mg/kg/day of actual body weight automatically.
- Read the maximum recommended dose in mg/day, calculated at 5.0 mg/kg/day of actual body weight.
Worked example — 70 kg, 50 kg, and 90 kg patients
A 70 kg patient: 70 × 5.0 = 350 mg/day is the maximum recommended dose under the current 2016 AAO guidance.
A lighter 50 kg patient: 50 × 5.0 = 250 mg/day — the same 5.0 mg/kg/day ceiling applied to a smaller patient's actual body weight, scaling the maximum dose down accordingly.
A heavier 90 kg patient: 90 × 5.0 = 450 mg/day. Because the formula uses actual weight, the ceiling scales up with a heavier patient's real weight; the prescribed dose is still typically rounded to an available tablet strength and may be set lower based on the treating clinician's judgment.
Questions
Why did the recommended maximum dose change in 2016?
The American Academy of Ophthalmology's 2016 revision (Marmor et al.) lowered the widely used maximum from roughly 6.5 mg/kg of ideal body weight to 5.0 mg/kg/day of actual (real) body weight. Both changes were made because dosing by actual weight correlated better with observed retinopathy risk in the data reviewed, and the lower multiplier further reduced the risk of retinal toxicity.
What is hydroxychloroquine retinopathy?
It's progressive damage to the retina that can occur with long-term hydroxychloroquine use, and it can be irreversible if not caught early. Risk increases with higher daily dose relative to body weight and with longer cumulative duration of treatment, which is why a weight-based dose ceiling and regular retinal screening are both part of standard long-term management.
Why does this calculator use actual (real) body weight instead of ideal body weight?
That's part of what the 2016 AAO revision changed. Earlier guidance calculated the maximum against ideal body weight, but the 2016 recommendations found that dosing by actual body weight correlated better with real-world retinopathy risk, so the current guidance is expressed in mg/kg of actual weight, not ideal weight.
What retinal screening is recommended for someone on long-term hydroxychloroquine?
Standard practice includes a baseline retinal exam around the time treatment starts, then annual screening beginning after five years of continuous use for patients without additional major risk factors (screening may start sooner if other risk factors, such as kidney disease or tamoxifen use, are present). Your ophthalmologist determines the specific tests and schedule.
Does staying under the calculated maximum guarantee no retinopathy risk?
No. Dose is one major risk factor among several, alongside cumulative duration of use, kidney function, concurrent tamoxifen use, and pre-existing retinal disease. Even at doses within the recommended ceiling, the 2016 guideline reports roughly 1% risk of retinopathy at 5 years and 2% at 10 years — lower than at higher doses, but not zero.
Who is this calculator for?
Clinicians and patients checking a prescribed dose against the published weight-based maximum. It is not a substitute for the prescribing decision itself, which also accounts for the condition being treated, kidney and liver function, other medications, and individual retinopathy risk factors.
Should I change my own dose based on this calculator?
No. Never adjust a prescribed medication dose without talking to the prescribing clinician first. This tool is meant as a reference for checking a prescribed dose against the published guideline maximum, not as a self-dosing tool.
References
- Marmor MF et al. (AAO) — HCQ Retinopathy Screening (2016). Ophthalmology 2016;123(6):1386-94. PMID 26992838
- MedlinePlus (U.S. National Library of Medicine) — Hydroxychloroquine drug information
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.