Resting Heart Rate of 55 BPM at Age 48: What It Means and What to Do

A resting heart rate (RHR) of 55 bpm is below the standard adult range of 60–100 bpm. In a 48-year-old woman, this warrants evaluation—though context determines significance.

Possible Benign Causes

• Athletic conditioning: Endurance athletes commonly 40–60 bpm (high vagal tone, stroke volume)
• Medications: β-blockers, calcium channel blockers, digoxin, clonidine, ivabradine
• High vagal tone: Yoga, meditation, breathwork practitioners

Potentially Concerning Causes

• Conduction abnormalities: Heart block, sick sinus syndrome
• Electrolyte imbalance: Hyperkalemia, hypercalcemia
• Endocrine: Hypothyroidism, adrenal insufficiency
• Medication toxicity: Digoxin, β-blocker overdose
• Infiltrative diseases: Amyloidosis, sarcoidosis
• Autonomic neuropathy: Diabetes, Parkinson's

Recommended Evaluation

1. Medication review — most common reversible cause
2. ECG — rhythm, intervals, conduction
3. Basic labs: CBC, CMP (K⁺, Ca²⁺, Mg²⁺, glucose), TSH, ferritin
4. Symptom correlation: Syncope, near-syncope, fatigue, exercise intolerance, dizziness, confusion
5. Ambulatory monitoring (Holter) if intermittent symptoms
6. Echocardiogram if structural concern

When It's Likely Benign

• Asymptomatic, long-distance runner/cyclist/swimmer
• On known rate-limiting medication, stable dose, no symptoms
• Consistently 50–60 for years, normal ECG

Action

Contact your primary care physician or cardiologist. Do not stop medications. Bring medication list, symptom diary, exercise log. Most causes are identifiable and manageable.