Drug Calculations

Loading Dose Calculator

First dose needed to reach a target drug level, from volume of distribution.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Turn on JavaScript to use this calculator, or open it in the web app.

Formula

Vd * Target Concentration

How it is used

• Loading dose = Vd × target concentration; when Vd is given in L/kg, multiply by weight first. Divide by bioavailability for an oral dose.
• A loading dose reaches the target level at once instead of after about five half-lives.
• It depends on volume, not clearance, so kidney failure seldom changes the loading dose; edema and ascites can enlarge Vd.

Same formula as the app. Open it in the web app.

Related one-pagers

• Mental Health: Meds and CommunicationFront-loading · Frequent large doses of diazepam or chlordiazepoxide · Severe (CIWA-Ar ≥19) or high risk
• CEN: Bites, Exposures and Wound CareNo control: repeat the same loading dose. Two doses fail: toxicologist or poison center.
• Endocrine EmergenciesIV levothyroxine loading dose, then daily; lower doses in older or cardiac patients
• Acute Kidney InjuryPharmacist review: full loading doses, adjusted maintenance, drug levels; avoid morphine and NSAIDs

Drip cards with a dose ↔ mL/h converter

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For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.