In a patient with a hemoglobin of 13 g/dL who feels dizzy and light‑headed on standing, what is the most likely diagnosis and how should orthostatic hypotension be evaluated and managed?

Orthostatic Hypotension Evaluation and Management

This patient's dizziness and lightheadedness with position changes is most likely orthostatic hypotension (OH), not anemia, since a hemoglobin of 13 g/dL is essentially normal and would not cause positional symptoms.

Diagnostic Confirmation

First, confirm OH by measuring blood pressure supine after 5 minutes of rest, then again at 1 and 3 minutes after standing 1. OH is defined as:

• Drop in systolic BP ≥20 mmHg OR
• Drop in diastolic BP ≥10 mmHg within 3 minutes of standing 1, 2

Important caveat: If bedside testing is negative but clinical suspicion remains high, proceed to head-up tilt table testing 2. Also screen for delayed OH (>3 minutes) and postprandial hypotension, as these frequently coexist 3, 4.

Determine the Underlying Cause

The key distinction is neurogenic versus non-neurogenic OH, as this determines prognosis and treatment approach 4:

Non-neurogenic OH (most common):

• Medications: Diuretics, vasodilators, antihypertensives, SGLT2 inhibitors 5, 6, 7
• Volume depletion: Dehydration, blood loss 1
• Metabolic: Check vitamin B12 levels even without anemia 8

Neurogenic OH:

• Autonomic dysfunction from diabetes, Parkinson's disease, multiple system atrophy, pure autonomic failure 5, 4
• Often presents with supine hypertension (critical to identify) 3, 4

Treatment Algorithm

Step 1: Remove Aggravating Factors

Review and discontinue or reduce offending medications first 3, 7. This includes diuretics, vasodilators, and other antihypertensives not essential for cardiovascular protection.

Step 2: Non-Pharmacological Interventions (First-Line)

These are recommended before any medications 5, 3, 4:

• Acute water ingestion: ≥480 mL provides temporary relief within 30 minutes (avoid adding glucose or salt, which reduces effectiveness) 5
• Increased salt intake: 6-9 grams (1-2 teaspoons) daily to expand plasma volume 5
• Compression garments: Must be at least thigh-high, preferably including abdomen (shorter garments ineffective) 5
• Physical counter-pressure maneuvers: Leg crossing, squatting, or lower body muscle tensing when prodromal symptoms occur 5
• Behavioral modifications: Avoid prolonged standing, rise slowly from supine/seated positions, avoid large meals and hot environments 3

Step 3: Pharmacological Treatment (If Non-Pharmacological Measures Fail)

For neurogenic OH specifically 5:

First-line medications:

• Midodrine: FDA-approved, dose-dependent BP increase. Watch for supine hypertension, scalp tingling, piloerection, urinary retention 5, 3
• Droxidopa: FDA-approved, effective for Parkinson's disease, pure autonomic failure, multiple system atrophy. May reduce falls. Avoid carbidopa in Parkinson's patients as it decreases droxidopa effectiveness 5, 3

Second-line:

• Fludrocortisone: Use only when supine hypertension is absent (it worsens supine hypertension). Increases plasma volume but causes edema, hypokalemia, and at doses >0.3 mg daily can cause adrenal suppression 5, 3

Critical Pitfalls to Avoid

1. Do not assume anemia is the cause with Hgb 13 g/dL—this is a normal value and positional symptoms point to OH 3
2. Always screen for supine hypertension before starting fludrocortisone or aggressive OH treatment, as this complicates management 3, 4, 7
3. Do not focus on blood pressure targets—treatment goals are symptom relief and fall prevention, not specific BP numbers 3
4. Screen high-risk groups even without symptoms: adults >70 years with frailty, neurodegenerative disorders, diabetes, unexplained falls 3, 2