Tamiflu (Oseltamivir)
Dose Calculator
Fast treatment dosing for infants, children and adults — with mg and mL per dose.
Use this free Tamiflu (oseltamivir) dose calculator to check standard treatment doses for term infants, children, adolescents and adults. It is designed for fast primary-care use in Malaysia and shows both the recommended dose in mg and the calculated liquid volume in mL.
Oseltamivir treatment dose
Oseltamivir treatment dosing
Usual oral treatment regimen for uncomplicated influenza: twice daily for 5 days.
| Patient | Dose | Frequency |
|---|---|---|
| Term infant <9 months | 3 mg/kg/dose | BD × 5 days |
| Term infant 9–11 months | 3.5 mg/kg/dose | BD × 5 days |
| 1–12 years, ≤15 kg | 30 mg | BD × 5 days |
| 1–12 years, >15–23 kg | 45 mg | BD × 5 days |
| 1–12 years, >23–40 kg | 60 mg | BD × 5 days |
| 1–12 years, >40 kg | 75 mg | BD × 5 days |
| ≥13 years / adult | 75 mg | BD × 5 days |
Important: premature infants require postmenstrual-age dosing and are intentionally excluded from the calculator. Renal impairment may require dose adjustment.
When to consider treatment
Start early
Clinical benefit is greatest when oseltamivir is started as soon as possible, particularly within 48 hours of symptom onset.
Do not delay in priority patients
Hospitalised, severe, complicated, progressive or higher-risk influenza warrants prompt antiviral consideration; treatment should not wait for laboratory confirmation when clinically indicated.
Reassess red flags
Respiratory distress, hypoxia, dehydration/shock, altered consciousness, persistent vomiting, chest pain or rapidly progressive illness should prompt escalation rather than routine outpatient management.
Before prescribing
Tamiflu / oseltamivir FAQ
Can oseltamivir still be started after 48 hours?
Yes, in selected patients. Benefit is greatest when started early, but later initiation may still be appropriate in high-risk, severe, progressive or hospitalised influenza. Use clinical judgement and the relevant guideline.
Should I wait for an influenza test result?
Not when antiviral treatment is clinically indicated in a priority patient. Current guidance supports starting treatment promptly without waiting for laboratory confirmation.
What dose is used in pregnancy?
Oseltamivir is the preferred oral antiviral for influenza during pregnancy in current CDC guidance. Standard adult treatment dosing is used when renal adjustment is not required.
Can I use this calculator for prophylaxis?
No. This calculator is intentionally limited to treatment dosing. Chemoprophylaxis differs in dose frequency, eligibility and duration.
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Clinical references
- Ministry of Health Malaysia. Paediatric Protocols for Malaysian Hospitals, 5th Edition — paediatric oseltamivir treatment dosing.
- Ministry of Health Malaysia. Garis Panduan Pengendalian Influenza di Klinik Kesihatan (Pindaan 7 Ogos 2023) — outpatient assessment and influenza management.
- CDC. Influenza Antiviral Medications: Summary for Clinicians — current antiviral treatment principles and special populations.
For healthcare professionals. This tool supports, but does not replace, clinical judgement. Verify dosing against the current product information and applicable MOH/local guidance, especially in premature infants, renal impairment, severe disease and unusual clinical circumstances.