How the dose is calculated
Fluconazole is dosed once daily in mg/kg, with the specific mg/kg figure and maximum dose depending on the indication and severity. Because fluconazole has a long elimination half-life (roughly 30 hours in adults), a higher loading dose on day 1 is commonly used for oropharyngeal and oesophageal candidiasis so therapeutic levels are reached faster, followed by a lower once-daily maintenance dose. The calculator above covers only once-daily regimens — total treatment duration (how many days or weeks the regimen continues) and the two once-weekly regimens that exist for this drug are covered separately below, since duration and weekly frequency aren't things a single per-dose calculation can capture.
Typical dosing by indication
| Indication | Dose | Frequency | Max | Duration |
|---|---|---|---|---|
| Oropharyngeal candidiasis — loading | 6 mg/kg | once, Day 1 | 400 mg | Day 1 only, then switch to maintenance below |
| Oropharyngeal candidiasis — maintenance | 3 mg/kg/day | once daily | 200 mg/day | 7–14 days total (including loading day) |
| Oesophageal candidiasis — maintenance | 6 mg/kg/day | once daily | 400 mg/day | 14–21 days total |
| Invasive/systemic candidiasis | 6–12 mg/kg/day | once daily | 800 mg/day | Per clinical response & culture clearance (often 2 weeks after first negative culture) |
| Tinea capitis — daily regimen | 6 mg/kg/day | once daily | 400 mg/day | ~20 days |
Every regimen above is dosed once daily — this calculator does not cover once-weekly regimens. Two common weekly fluconazole regimens exist and are not represented by the daily calculator above:
| Indication | Dose | Frequency | Duration |
|---|---|---|---|
| Tinea capitis — weekly alternative | 6 mg/kg (weight-based) | once weekly | 8–12 weeks |
| Recurrent vulvovaginal candidiasis — maintenance | 150 mg (fixed adult dose) | once weekly | 6 months |
For the weekly tinea capitis regimen, enter the weight and use the same 6 mg/kg figure from the daily row above — only the frequency changes (once weekly instead of once daily), so calculate the per-dose amount using the daily calculator and disregard its "per day" labelling for this specific regimen.
Fixed adult dosing (not weight-based)
Some common adult indications use a fixed dose rather than mg/kg — these aren't covered by the calculator above since they don't scale with weight.
| Indication | Dose | Duration |
|---|---|---|
| Vulvovaginal candidiasis | 150 mg | single oral dose |
| Recurrent vulvovaginal candidiasis — maintenance | 150 mg once weekly | 6 months |
| Oesophageal candidiasis (adult) | 200 mg Day 1, then 100–400 mg once daily | 14–21 days |
| Candidaemia (adult) | 800 mg loading, then 400 mg once daily | per clinical response |
Clinical use
- Fluconazole is first-line for most mucosal Candida infections (oropharyngeal, oesophageal, vulvovaginal) because of excellent oral bioavailability and a simple once-daily regimen.
- It is not reliably active against Candida krusei or many Candida glabrata isolates — local antifungal susceptibility patterns should guide empirical choice in severe or refractory infection.
- High-dose or prolonged fluconazole in pregnancy (especially the first trimester) has been associated with a rare pattern of congenital anomalies — a single low-dose (150 mg) course for vaginal candidiasis is generally considered lower risk, but avoid unless clearly needed.
- Dose reduction is required in significant renal impairment (fluconazole is predominantly renally cleared) — verify against local renal dosing guidance.
Frequently asked questions
What is the usual paediatric fluconazole dose?
For oropharyngeal candidiasis, 6 mg/kg (max 400 mg) as a loading dose on day 1, then 3 mg/kg (max 200 mg) once daily as maintenance. Invasive candidiasis uses a higher range, 6–12 mg/kg/day. Select the matching indication above and enter the weight for the exact figure.
Why is a loading dose used for fluconazole?
Fluconazole's elimination half-life is roughly 30 hours, so once-daily maintenance dosing alone would take several days to reach steady-state blood levels. A higher first-day loading dose (typically double the maintenance dose) reaches effective concentrations faster.
What is the single-dose fluconazole regimen for vaginal candidiasis?
150 mg as a single oral dose — this is a fixed adult dose, not weight-based, and is one of the most common outpatient antifungal regimens prescribed.
Is fluconazole dosed daily or weekly?
Most indications (oropharyngeal/oesophageal/invasive candidiasis, the daily tinea capitis regimen) are dosed once daily — that's what the calculator above computes. Two indications instead use a once-weekly schedule: a weekly tinea capitis alternative (6 mg/kg once weekly for 8–12 weeks) and recurrent vulvovaginal candidiasis maintenance therapy (150 mg once weekly for 6 months, a fixed adult dose). See the "Duration" and weekly-regimen tables above for the full picture before assuming every course is a simple daily count.
How many days is a typical fluconazole course?
It varies by indication: oropharyngeal candidiasis is usually 7–14 days total, oesophageal candidiasis 14–21 days, tinea capitis around 20 days (daily regimen) or 8–12 weeks (weekly regimen), and invasive candidiasis continues per clinical response and culture clearance rather than a fixed day count. Recurrent vulvovaginal candidiasis maintenance therapy runs much longer — 6 months of once-weekly dosing.
Can fluconazole be taken with food?
Yes — fluconazole absorption is not significantly affected by food, so it can be taken with or without meals.
Is fluconazole safe in pregnancy?
A single low-dose (150 mg) course for vaginal candidiasis is generally considered lower risk, but high-dose or prolonged courses — particularly in the first trimester — have been associated with a rare pattern of congenital anomalies. Discuss alternatives with the prescriber if pregnancy is confirmed or suspected.
References
- Pappas PG, et al. Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the IDSA. Clin Infect Dis. 2016.
- British National Formulary for Children (BNFC) — Fluconazole.
- Tripathi KD. Essentials of Medical Pharmacology, 8th edition — Antifungal agents, azoles.