Hydroxychloroquine Dose Calculator
Enter your weight and current daily dose to see whether your hydroxychloroquine prescription stays within the American Academy of Ophthalmology safe limit of 5 mg/kg per day. The calculator also shows your maximum allowable dose, mg-per-kg ratio, retinopathy risk category, and cumulative dose if you enter years of use. Switch between kilograms and pounds at the top.
What is hydroxychloroquine and why does the dose matter?
Hydroxychloroquine (sold as Plaquenil) is an antimalarial drug widely used to treat autoimmune conditions including systemic lupus erythematosus (SLE), rheumatoid arthritis, Sjogren syndrome, and dermatomyositis. It suppresses immune system overactivity and reduces inflammation. Because the drug accumulates in the retinal pigment epithelium over time, taking too high a daily dose or continuing for many years without monitoring increases the risk of hydroxychloroquine retinopathy, a form of irreversible damage to the macula that can cause permanent vision loss. Getting the dose right relative to body weight is the single most important way to reduce that risk.
The AAO 5 mg/kg guideline and the old 6.5 mg/kg rule
Before 2016, many prescribers followed a limit of 6.5 mg/kg of ideal or lean body weight per day. The American Academy of Ophthalmology revised this in 2016 based on large-scale retinopathy data, tightening the limit to 5 mg/kg of actual (real) body weight per day, with an absolute cap of 400 mg per day. The switch from ideal to actual weight matters: a taller, heavier patient under the old rule would have received a proportionally larger dose than was safe. Using actual weight and the lower 5 mg/kg threshold has been shown to reduce the 10-year retinopathy rate from around 10% (at higher doses) to under 2%. Doses approaching 6 mg/kg/day or above markedly accelerate risk regardless of duration.
How to use this calculator
Select your weight unit, enter your body weight, then type your current daily dose. The calculator instantly shows the maximum safe dose for your weight, your dose expressed as mg/kg/day, how far above or below the limit you are, and a retinopathy risk category. If you enter how long you have been taking hydroxychloroquine, it also calculates your cumulative dose in grams and refines the risk estimate. You can flag additional risk factors (such as renal impairment or concurrent tamoxifen use) to reflect that your personal risk may be higher than the duration alone suggests. The chart below the results shows how your cumulative dose would compare with the safe-limit trajectory over 20 years of use.
Screening and monitoring recommendations
The AAO recommends a baseline ophthalmology exam, including optical coherence tomography (OCT), fundus autofluorescence (FAF), and visual field testing, soon after starting hydroxychloroquine. Annual screening can often be deferred for the first 5 years when there are no additional risk factors and the dose is within limits. From year 5 onward, annual retinal screening is recommended for all patients. Patients with one or more additional risk factors (kidney disease, concurrent tamoxifen use, pre-existing retinal disease, age over 60, or obesity) should begin annual screening earlier. Retinopathy detected early, before it is visible on dilated exam, can sometimes be slowed or halted by dose reduction. Once visible retinal damage is present, some progression may continue even after the drug is stopped.
Hydroxychloroquine retinopathy risk by dose and duration
| Daily dose | Duration | Approximate retinopathy risk | Risk level |
|---|---|---|---|
| <=5 mg/kg/day | First 5 years | Below 1% | Low |
| <=5 mg/kg/day | 5-10 years | Under 2% | Low-moderate |
| <=5 mg/kg/day | Over 20 years | Almost 20% (cumulative) | Moderate |
| >5 mg/kg/day | First 5 years | Elevated above baseline | Elevated |
| >5 mg/kg/day | Over 10 years | Up to 10% | High |
| >6 mg/kg/day | Any duration | Markedly higher | High |
Based on AAO 2016 guideline data. Risk percentages apply to patients dosed at or near the safe limit. Higher doses accelerate risk considerably.
Frequently asked questions
Should I use my actual weight or my ideal body weight for this calculation?
Use your actual (real) body weight. The 2016 AAO guideline explicitly changed from ideal body weight to actual body weight as the basis for the 5 mg/kg limit. The only exception is for severely obese patients, where the guideline recommends erring toward a lower calculated dose and maintaining the 400 mg/day hard cap, because drug distribution at very high body mass is less predictable.
What is a safe daily dose of hydroxychloroquine?
For most adults, the maximum safe dose is 5 mg/kg of actual body weight per day, with an absolute ceiling of 400 mg/day. For a person weighing 60 kg that is 300 mg/day; for 70 kg it is 350 mg/day; for 80 kg or more it is capped at 400 mg/day. Common prescriptions of 200 mg or 400 mg per day are within the limit for most patients, but anyone weighing under 40 kg may need a lower dose.
What is hydroxychloroquine retinopathy?
Hydroxychloroquine retinopathy is damage to the macula, the central part of the retina, caused by the drug accumulating in retinal pigment epithelial cells over time. Early changes are often asymptomatic and detectable only by specialized imaging (OCT or fundus autofluorescence). Advanced retinopathy causes a characteristic "bull's eye" maculopathy and can lead to loss of central vision. Because the damage is irreversible and may continue after the drug is stopped, prevention through correct dosing and regular screening is essential.
How does treatment duration affect retinopathy risk?
Even at the safe 5 mg/kg/day dose, retinopathy risk accumulates over time because the drug builds up in retinal tissue. The AAO 2016 statement puts the risk at under 1% for the first 5 years and under 2% up to 10 years, but says it rises to almost 20% after 20 years of use. Reassuringly, a patient who is still free of toxicity at 20 years has only about a 4% chance of developing it in the following year. At doses above 5 mg/kg/day the Kaplan-Meier curves climb far more steeply, reaching roughly 40% by around 20 years. Duration of treatment is therefore a key reason why ophthalmology monitoring should continue throughout the course of therapy.
What are the additional risk factors for retinopathy?
Several factors independently increase retinopathy risk above what dose and duration alone would predict: chronic kidney disease (the drug is cleared renally and can accumulate further), concurrent tamoxifen use (a major synergistic risk factor), pre-existing retinal or macular disease, age over 60, and obesity. Patients with any of these should discuss earlier and more frequent ophthalmology screening with their eye doctor.
What is the cumulative dose and why does it matter?
Cumulative dose is the total amount of hydroxychloroquine taken over the entire treatment period, expressed in grams. Some ophthalmologists use a cumulative dose threshold of around 1,000 g as a rough marker for increased retinopathy risk, regardless of daily dose or years alone. At a typical dose of 400 mg/day, 1,000 g is reached in about 6.8 years. At a lower dose of 200 mg/day, it takes about 13.7 years. The calculator above shows your estimated cumulative dose when you enter your years of use.