Digoxin Dosing Calculator

Enter patient weight, age, dose rate, and renal function to calculate the adjusted digoxin dose, estimated steady-state plasma level, and key pharmacokinetic parameters.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter Patient Weight (kg)
Input the patient's body weight in kilograms. This is fundamental for weight-based dosing calculations.
2
Specify Dose Rate (mcg/kg/day)
Enter the target digoxin dose rate in micrograms per kilogram per day, typically 2.5–5 mcg/kg/day for heart failure or lower for rate control.
3
Input Patient Age (years)
Provide the patient's age in years. Age influences drug metabolism and distribution, particularly in elderly patients.
4
Select Renal Function
Choose the patient's renal function level from the provided options (Normal, Mild, Moderate, Severe Impairment), as kidney function significantly impacts digoxin clearance.
5
Review Digoxin Dosing Plan
The calculator displays the adjusted daily dose in mg and mcg, estimated steady-state level, half-life, volume of distribution, and adjusted dose rate.

Example Calculation

A 45-year-old patient weighing 70 kg with normal renal function requires digoxin for heart failure, with a target dose rate of 5 mcg/kg/day.

Patient Weight (kg)

Dose Rate (mcg/kg/day)

Patient Age (years)

Renal Function (select)

Normal (CrCl > 60 mL/min)

Results

0.35 mg/day

Tips

Monitor Serum Digoxin Levels

Always monitor serum digoxin levels, especially during initiation and with changes in renal function or interacting medications. The therapeutic range is narrow (0.5–2.0 ng/mL), and levels above 2.0 ng/mL significantly increase toxicity risk.

Consider Drug Interactions

Digoxin has numerous drug interactions that can alter its concentration. Medications like amiodarone, verapamil, and quinidine can increase digoxin levels, necessitating a dose reduction. Always review the patient's full medication list.

Clinical Assessment is Key

While calculations provide a starting point, clinical assessment of the patient's response and tolerance is paramount. Adjust doses based on therapeutic effect, adverse reactions, and serum levels, not solely on calculated values. Consult a licensed pharmacist or physician for all dosing decisions.

The Digoxin Dosing Calculator is an essential clinical tool designed to assist healthcare professionals in precisely determining appropriate digoxin maintenance doses for patients. By integrating critical patient parameters such as weight, age, and renal function, it provides calculated insights into adjusted daily doses, estimated steady-state levels, and drug half-life. This precision is vital for optimizing therapy, minimizing the risk of toxicity, and ensuring patient safety in the complex landscape of cardiac medication management in 2025.

Optimizing Digoxin Therapy for Cardiac Conditions

Digoxin is a potent cardiac glycoside used to manage heart failure and control ventricular rate in atrial fibrillation. Its narrow therapeutic index means that the difference between an effective dose and a toxic dose is very small, typically between 0.5–2.0 ng/mL. This necessitates highly individualized dosing, with careful consideration of patient-specific factors. For instance, elderly patients or those with compromised renal function require significantly lower doses due to reduced drug clearance. A dose of 0.125 mg/day might be appropriate for a patient with normal renal function, while a patient with severe renal impairment might need only 0.0625 mg/day or less to avoid accumulation.

The Pharmacokinetic Formulas Behind Digoxin Dosing

Digoxin dosing involves several pharmacokinetic principles, particularly how the drug is absorbed, distributed, metabolized, and excreted. The calculator integrates these principles to estimate an appropriate maintenance dose and predict steady-state concentrations.

Key formulas used in the calculation:

Adjusted Daily Dose (mcg/kg/day):

Adjusted Dose Rate = Standard Dose Rate × Renal Adjustment Factor

Total Daily Dose (mcg):

Daily Dose (mcg) = Patient Weight (kg) × Adjusted Dose Rate (mcg/kg/day)

Volume of Distribution (Vd): Vd is adjusted by age (e.g., 7.3 L/kg for younger adults, 6.0 L/kg for elderly).
```
Vd Total (L) = Vd per kg (L/kg) × Patient Weight (kg)
```
Estimated Steady-State Level (Css in ng/mL):
```
Css (ng/mL) = (Bioavailability × Daily Dose (mcg)) / (Vd Total (L) × Elimination Rate Constant (per day))
```
The Elimination Rate Constant is derived from the Half-Life, which also varies with renal function.

💡 For other medications requiring precise weight-based administration, our Medication Dosage by Weight Calculator can help ensure accurate dosing.

Dosing Digoxin for a Geriatric Patient: A Worked Example

Consider an 80-year-old patient weighing 60 kg with moderate renal impairment (CrCl 15–30 mL/min), requiring digoxin for rate control at a standard dose rate of 2.5 mcg/kg/day.

Identify Patient Weight: 60 kg.
Identify Dose Rate: 2.5 mcg/kg/day.
Identify Patient Age: 80 years.
Identify Renal Function: Moderate Impairment.
- Renal Adjustment Factor for moderate impairment is 0.5.
- Vd per kg for age 80 is 6.0 L/kg.
- Half-Life for moderate impairment is 73 hours.
Calculate Adjusted Dose Rate: 2.5 mcg/kg/day × 0.5 = 1.25 mcg/kg/day.
Calculate Daily Dose (mcg): 60 kg × 1.25 mcg/kg/day = 75 mcg/day.
Calculate Daily Dose (mg): 75 mcg / 1000 = 0.075 mg/day.
Calculate Total Vd: 6.0 L/kg × 60 kg = 360 L.
Calculate Elimination Rate Constant (ke): 0.693 / (73 hours / 24 hours/day) ≈ 0.227 per day.
Calculate Estimated Steady-State Level (Css): Css = (0.7 × 75 mcg) / (360 L × 0.227 per day) = 52.5 / 81.72 ≈ 0.64 ng/mL.

The Adjusted Daily Dose is 0.075 mg/day, with an Estimated Steady-State Level of 0.64 ng/mL, which falls within the lower end of the therapeutic range (0.5–2.0 ng/mL).

💡 To ensure a medication achieves its intended effect without underdosing, our Minimum Effective Dose Calculator can help determine the lowest necessary dose.

The Historical Context of Digoxin Therapy

Digoxin is one of the oldest cardiac medications still in use, with its origins tracing back to the discovery of foxglove (Digitalis purpurea) by William Withering in 1785. Withering, an English physician, documented its effectiveness in treating "dropsy" (edema) and heart failure. For centuries, digitalis extracts were used with varying success and significant toxicity due to inconsistent potency. It wasn't until the early 20th century that pure digoxin was isolated, allowing for standardized dosing and a better understanding of its pharmacokinetics. Despite the advent of newer heart failure medications, digoxin remains a vital drug, particularly for symptom control in patients with advanced heart failure and for rate control in atrial fibrillation, a testament to its enduring legacy in cardiology spanning over two centuries.

Frequently Asked Questions

What is the Digoxin Dosing Calculator used for?

The Digoxin Dosing Calculator helps healthcare professionals determine an appropriate maintenance dose of digoxin for patients, taking into account crucial factors like patient weight, age, and renal function. It provides estimations for the adjusted daily dose, steady-state drug levels, and half-life, aiding in safe and effective medication management in 2025.

Why is renal function a critical factor in digoxin dosing?

Digoxin is primarily eliminated by the kidneys, so impaired renal function significantly prolongs its half-life and increases the risk of accumulation and toxicity. Patients with reduced kidney function require lower doses and careful monitoring to maintain therapeutic levels within the narrow therapeutic window and prevent adverse drug reactions.

What is the therapeutic range for digoxin and why is it narrow?

The therapeutic range for digoxin is typically 0.5–2.0 ng/mL, which is considered very narrow. This means there is a small difference between a dose that is effective and one that causes toxicity. Levels below 0.5 ng/mL may not be effective, while levels above 2.0 ng/mL significantly increase the risk of serious adverse effects like cardiac arrhythmias, necessitating precise dosing and close monitoring.