Digoxin Level: Normal Range, Toxicity & What Results Mean
Everything you need to know about Digoxin Level: Normal Range, Toxicity & What Results Mean test results, including normal ranges and what abnormal levels might mean.
Reference Range
Unit: ng/mLReference Range
Reference ranges vary by laboratory. Always consult your healthcare provider for interpretation of your specific results.
What is Digoxin?
Digoxin is one of the oldest medications still in use today. Derived from the foxglove plant, it's been used for heart conditions for over 200 years. Despite its age, digoxin remains an important medication for certain heart conditions.
What digoxin does:
- Strengthens heart contractions (positive inotrope)
- Slows heart rate (negative chronotrope)
- Helps control heart rhythm in atrial fibrillation
- Improves symptoms of heart failure
What digoxin testing does: The digoxin level test measures the amount of digoxin in your blood. Because digoxin has a narrow therapeutic window—meaning the effective dose is close to the toxic dose—monitoring blood levels is essential for safety.
Narrow Therapeutic Index
Digoxin has a narrow therapeutic index. The therapeutic range (0.5-2.0 ng/mL) is close to the toxic range (＞2.0 ng/mL). Small changes in dose, kidney function, or electrolyte balance can push levels from therapeutic to toxic. This is why monitoring is essential.
Understanding Your Results
Digoxin is measured in nanograms per milliliter (ng/mL).
Understanding Your Results (ng/mL)
May be ineffective—dose may need adjustment
Effective range—most patients target 0.8-1.5
Toxicity risk—symptoms likely, may need dose reduction
Signs of Digoxin Toxicity
Digoxin toxicity can be serious and even life-threatening. Symptoms include:
Early/mild toxicity:
- Nausea, vomiting, diarrhea
- Loss of appetite
- Fatigue, weakness
- Headache, dizziness
- Visual changes (yellow/green halos around lights, blurred vision)
- Confusion
Severe toxicity:
- Life-threatening heart rhythm abnormalities
- Very slow heart rate (＜60 bpm)
- Heart block
- Ventricular arrhythmias
- Hyperkalemia (high potassium)
- Death (if untreated)
When Digoxin Toxicity Requires Urgent Evaluation
- Digoxin level above 2.0 ng/mL with any symptoms
- Severe nausea, vomiting, or diarrhea
- Visual disturbances (halos, blurred vision, color changes)
- Very slow heart rate (<50 bpm) or irregular heartbeat
- Confusion, extreme weakness, or fainting
- Known overdose or accidental double dose
⚠️ Seek immediate medical attention. Digoxin toxicity can be life-threatening. Call emergency services for severe symptoms or contact your doctor promptly for any concerning symptoms.
Factors Affecting Digoxin Levels
Many factors can affect digoxin levels, pushing them from therapeutic to toxic:
Factors That Increase Digoxin Levels (Toxicity Risk)
| Factor | Effect | What to Do |
|---|---|---|
| Kidney dysfunction | Increases | Digoxin is cleared by kidneys. Reduced kidney function causes accumulation. Dose reduction and closer monitoring needed when creatinine elevated or eGFR decreased. |
| Drug interactions | Increases | Many drugs increase digoxin: amiodarone, quinidine, verapamil, diltiazem, erythromycin, certain antifungals. Dose reduction needed when starting these drugs. |
Always tell your doctor about medications, supplements, and recent health events before testing.
Timing of Digoxin Testing
Digoxin level should be measured at least 6-8 hours after the last dose (ideally 12-24 hours after). Testing too soon after a dose falsely elevates the result. Levels are typically drawn just before the next dose is due (trough level).
When is Digoxin Level Ordered?
Doctors order digoxin levels in several situations:
When Your Doctor Might Check Digoxin Level
Digoxin monitoring is essential for safe treatment.
You just started taking digoxin
Initial level is checked after reaching steady state (about 1 week of daily dosing). This establishes that the dose is therapeutic and not toxic.
Your digoxin dose was changed
After any dose change, recheck level in 1-2 weeks to ensure new dose is therapeutic. This prevents underdosing or toxicity.
You have symptoms of digoxin toxicity
Nausea, visual changes, or heart rhythm changes prompt level checking. If elevated, dose is reduced or medication temporarily stopped.
Your kidney function changed
Since digoxin is cleared by kidneys, any change in kidney function (creatinine, eGFR) warrants level checking. Dose adjustment may be needed.
You started a medication that interacts with digoxin
Many drugs affect digoxin levels. Amiodarone, quinidine, verapamil, diltiazem, and certain antibiotics can raise digoxin levels. Check level after starting interacting medications.
You have atrial fibrillation with poor rate control
If heart rate remains rapid despite digoxin, level checking ensures the dose is adequate. Subtherapeutic levels may require dose increase.
Your Action Plan Based on Results
If your digoxin level is below 0.5 ng/mL (Subtherapeutic):
- May be ineffective for heart failure or atrial fibrillation control
- Discuss with your doctor—dose increase may be needed
- Recheck level 1-2 weeks after any dose change
- Consider if symptoms are still present despite medication
If your digoxin level is 0.5-2.0 ng/mL (Therapeutic):
- Continue current dose
- Periodic monitoring still needed (every 6-12 months if stable)
- Report any concerning symptoms to your doctor immediately
- Maintain stable kidney function and electrolytes
- Be cautious with new medications that may interact
If your digoxin level is above 2.0 ng/mL (Potential Toxicity):
- Contact your doctor promptly
- Dose reduction or temporary discontinuation likely needed
- Monitor for symptoms of toxicity
- Check potassium and magnesium levels
- ECG monitoring may be needed
- For severe toxicity (＞4.0 ng/mL with symptoms), hospitalization and digoxin-specific antibody fragments (Digibind) may be needed
If you have symptoms regardless of level:
- Report symptoms to your doctor
- Even therapeutic levels can cause toxicity if potassium is low
- Clinical picture matters more than the number alone
- When in doubt, seek evaluation
Treatment of Digoxin Toxicity
Treatment depends on severity:
Mild toxicity (level 2.0-3.0 ng/mL, minimal symptoms):
- Stop digoxin temporarily
- Monitor heart rhythm and symptoms
- Correct low potassium and magnesium
- Restart at lower dose after symptoms resolve
Moderate toxicity (level 3.0-4.0 ng/mL, concerning symptoms):
- Discontinue digoxin
- Hospitalization for monitoring
- Correct electrolyte abnormalities
- Consider digoxin-specific antibody fragments if severe
- May need temporary cardiac pacing for heart block
Severe toxicity (level ＞4.0 ng/mL, life-threatening symptoms):
- Hospitalization in intensive care
- Digoxin-specific antibody fragments (Digibind)
- Cardiac monitoring and support
- Treatment of arrhythmias and heart block
- Hemodialysis (rarely needed, Digibind is preferred)
Drug Interactions
Many medications interact with digoxin:
Medications that INCREASE digoxin levels:
- Amiodarone, quinidine, dronedarone (antiarrhythmics)
- Verapamil, diltiazem (calcium channel blockers)
- Erythromycin, clarithromycin, azithromycin (antibiotics)
- Itraconazole, ketoconazole (antifungals)
- Cyclosporine, tacrolimus (immunosuppressants)
- Spironolactone (potassium-sparing diuretic)
Medications that DECREASE digoxin levels:
- Certain antacids and binders (cholestyramine)
- St. John's wort
- Rifampin
- Certain anti-seizure medications
Medications that increase toxicity risk without changing levels:
- Diuretics (cause low potassium and low magnesium)
- Beta-blockers, calcium channel blockers (additive heart rate slowing)
Always Tell Your Doctor About New Medications
Before starting any new medication (prescription or over-the-counter), tell your doctor you take digoxin. Many common drugs interact with digoxin, requiring dose adjustments or closer monitoring. This includes antibiotics, antifungals, heart medications, and herbal supplements.
Common Questions
Disclaimer: This information is for educational purposes only and does not constitute medical advice. Always consult your healthcare provider to interpret your digoxin level and determine appropriate management.
Track Your Digoxin Level Results
Monitor your levels over time, identify trends, and share your history with your doctor.