What laboratory tests are recommended for a hypertension workup?

Laboratory Tests for Hypertension Workup

All patients with newly diagnosed hypertension should undergo basic laboratory testing including serum sodium, potassium, creatinine with eGFR, fasting glucose, lipid profile, urinalysis, and a 12-lead ECG, with additional testing reserved for those with clinical features suggesting secondary causes or target organ damage. 1

Essential Basic Laboratory Tests

The following tests should be performed in all patients at initial hypertension evaluation:

Blood Tests (Required)

• Serum electrolytes: Sodium and potassium 1
• Renal function: Serum creatinine with calculated eGFR 1
• Fasting blood glucose (or HbA1c if available) 1
• Lipid profile: Total cholesterol, LDL, HDL, triglycerides 1

Additional Recommended Tests

• Complete blood count 2
• Thyroid-stimulating hormone (TSH) 1, 2
• Liver function tests 1, 2

Urine Testing

• Urinalysis (dipstick) 1
• Urinary albumin-to-creatinine ratio (UACR) - This is superior to dipstick alone for detecting early kidney damage and should be performed instead of or in addition to dipstick 1, 2

Cardiac Assessment

• 12-lead electrocardiogram to detect atrial fibrillation, left ventricular hypertrophy, or ischemic heart disease 1, 2

Rationale for Each Test

Why These Tests Matter for Outcomes

Renal function tests (creatinine, eGFR, UACR) identify kidney damage from hypertension and guide medication choices, particularly before starting ACE inhibitors, ARBs, or diuretics 1, 2. Elevated creatinine or reduced eGFR indicates existing target organ damage and significantly influences treatment decisions 2.

Electrolytes are critical because hypokalemia may indicate primary aldosteronism (a treatable secondary cause affecting 8-20% of resistant hypertension), while baseline values are essential before initiating diuretics or RAS blockers 1, 2, 3.

Glucose/HbA1c identifies comorbid diabetes, which dramatically increases cardiovascular risk and necessitates more aggressive blood pressure targets 1, 2. Recent data shows 8.4% of newly diagnosed hypertensive patients have undiagnosed diabetes 4.

Lipid profile assesses cardiovascular risk and guides decisions about statin therapy in addition to blood pressure management 1, 2. Over 30% of hypertensive patients have dyslipidemia 1.

UACR detects albuminuria (even at low levels), which indicates both kidney damage and heightened cardiovascular risk, and may guide selection of ACE inhibitors or ARBs 1, 2. This test is more sensitive than dipstick for early detection 1.

TSH screens for thyroid disorders, which can cause or exacerbate hypertension 2.

Additional Testing Based on Clinical Suspicion

When to Suspect Secondary Hypertension

Order additional tests if the patient has:

• Age of onset <30 years or abrupt onset at any age 2, 3, 5
• Resistant hypertension (uncontrolled on ≥3 medications including a diuretic) 3, 5
• Sudden deterioration in previously controlled hypertension 3, 5
• Hypertensive emergency 3, 5
• Target organ damage disproportionate to duration/severity of hypertension 3, 5

Specific Tests for Secondary Causes

For primary aldosteronism (suspect if hypokalemia, muscle weakness, resistant hypertension):

• Plasma aldosterone-to-renin ratio 1, 3, 5

For pheochromocytoma (suspect if episodic symptoms, sweating, palpitations, headaches):

• Plasma free metanephrines or 24-hour urinary catecholamines 1, 3, 5

For Cushing syndrome (suspect if weight gain, striae, moon facies):

• Late-night salivary cortisol or other cortisol screening tests 1

For renovascular disease (suspect if abrupt onset, flash pulmonary edema, early-onset in women):

• Renal ultrasound with Duplex Doppler, followed by CT or MR angiography if positive 3, 5

Optional Tests for Target Organ Assessment

Echocardiography if ECG is abnormal, cardiac murmurs detected, or cardiac symptoms present 1, 2

Fundoscopy in severe hypertension to assess for retinopathy, hemorrhages, or papilledema 1, 2

Serum uric acid - Elevated in 25% of hypertensive patients and associated with increased cardiovascular risk 1

Clinical Impact of Laboratory Findings

Recent evidence demonstrates that complete baseline laboratory workup significantly improves blood pressure control. Patients receiving complete testing achieved systolic BP of 129.9 mmHg at 12 months versus 142.8 mmHg in those with partial workup (P = 0.003) 4.

Common Abnormalities Detected

In newly diagnosed hypertensive patients, baseline testing reveals:

• 54.2% have LDL cholesterol >100 mg/dL 4
• 35.5% have elevated creatinine 4
• 8.4% have undiagnosed diabetes (glucose >125 mg/dL) 4
• 7.5% have reduced eGFR <60 mL/min/1.73m² 4
• 7.5% have proteinuria 1

Critical Pitfalls to Avoid

Do not use urine dipstick alone - UACR is more sensitive for detecting early kidney damage and should be the preferred test 1. Moderately elevated UACR (30-300 mg/g) indicates end-organ damage and heightened cardiovascular risk even when dipstick is negative 1.

Obtain baseline values before starting medications - This is essential for monitoring medication side effects, particularly electrolytes and renal function before diuretics or RAS blockers 2.

Do not perform expensive imaging before basic laboratory screening - Complete the basic workup first, then proceed to targeted testing based on clinical suspicion 3, 5.

Screen for medication-induced hypertension before extensive secondary workup - Review all medications including NSAIDs, oral contraceptives, decongestants, and supplements 5.

Consider obstructive sleep apnea in resistant hypertension, especially with obesity, snoring, and daytime sleepiness - This affects 25-50% of resistant hypertension cases 3.