What labs should be run for the evaluation of hypertension (HTN)?

Laboratory Evaluation for Hypertension

All patients with newly diagnosed hypertension should undergo a standardized panel of basic laboratory tests to assess cardiovascular risk, detect target organ damage, screen for secondary causes, and establish baseline values before initiating treatment. 1, 2

Essential Basic Laboratory Tests

The following tests should be obtained for every patient with hypertension:

Blood Tests

• Fasting blood glucose (or HbA1c): Screens for diabetes/prediabetes, which coexists in 15-20% of hypertensive patients and significantly increases cardiovascular risk 1, 2, 3
• Complete blood count (CBC): Evaluates for anemia or hematologic abnormalities that may affect treatment decisions 1, 2, 3
• Lipid profile (total cholesterol, LDL, HDL, triglycerides): Essential for cardiovascular risk stratification, as 30% of hypertensive patients have dyslipidemia 1, 2, 3
• Serum creatinine with estimated glomerular filtration rate (eGFR): Assesses kidney function and establishes baseline renal status before medication initiation 1, 2, 3
• Serum electrolytes (sodium, potassium, calcium): Critical for identifying secondary causes like primary aldosteronism (hypokalemia) and monitoring during diuretic or RAS blocker therapy 1, 2, 3
• Thyroid-stimulating hormone (TSH): Screens for thyroid disorders, which are remediable causes of hypertension 1, 2, 3

Urine Tests

• Urinalysis (dipstick): Screens for kidney disease and hematuria 1, 3

Cardiac Assessment

• 12-lead electrocardiogram (ECG): Detects left ventricular hypertrophy, atrial fibrillation, and ischemic heart disease 1, 2, 4, 3

Optional Tests for Enhanced Risk Stratification

These tests provide additional prognostic information and should be considered based on clinical context:

• Urinary albumin-to-creatinine ratio: More sensitive than dipstick urinalysis for detecting early kidney damage; strongly recommended for patients with diabetes, chronic kidney disease, or high cardiovascular risk 1, 2, 4, 3
• Serum uric acid: May provide additional risk stratification information, as hyperuricemia is present in 25% of hypertensive patients 1, 2
• Liver function tests: Useful for baseline assessment, particularly if considering medications metabolized hepatically 1, 3

Additional Testing Based on Specific Clinical Scenarios

When to Order Echocardiography

• Uncontrolled hypertension despite treatment 2, 4
• Abnormal ECG findings 4, 3
• Cardiac murmurs or symptoms suggesting heart failure 4, 3
• Clinical suspicion of left ventricular hypertrophy that would influence treatment decisions 4

When to Suspect Secondary Hypertension

Order targeted testing when clinical features suggest specific causes:

• Primary aldosteronism: Hypokalemia, muscle weakness, or resistant hypertension → aldosterone-renin ratio 1, 3
• Pheochromocytoma: Episodic headaches, sweating, palpitations → plasma free metanephrines 1
• Cushing syndrome: Central obesity, facial rounding, easy bruising → late-night salivary cortisol or 24-hour urinary free cortisol 1
• Renal artery stenosis: Flash pulmonary edema, resistant hypertension, elevated creatinine after ACE inhibitor → renal artery imaging 1
• Obstructive sleep apnea: Snoring, daytime sleepiness, neck circumference >40 cm → sleep study 1, 4

When to Order Renal Imaging

• Age <30 years with hypertension 2
• Poor response to standard treatment 2
• Abnormal kidney function tests 2, 4
• Suspected secondary hypertension 2, 4

Clinical Implications of Laboratory Findings

Understanding test results guides management decisions:

• Hypokalemia (<3.5 mEq/L): Suggests primary aldosteronism; warrants aldosterone-renin ratio 3
• Elevated creatinine or reduced eGFR (<60 mL/min/1.73m²): Indicates kidney damage; influences medication selection and blood pressure targets 4, 3
• Proteinuria or albuminuria: Independent cardiovascular risk factor requiring more aggressive blood pressure control 4, 3
• Elevated glucose or HbA1c: Identifies comorbid diabetes; lowers treatment thresholds and influences medication choice 4, 3
• Abnormal lipids: Guides statin therapy decisions in addition to blood pressure management 3

Critical Pitfalls to Avoid

• Do not rely solely on office blood pressure measurements: Confirm diagnosis with home or ambulatory blood pressure monitoring to avoid misdiagnosing white coat or masked hypertension 2
• Do not use urine dipstick alone: Quantitative urinary albumin-to-creatinine ratio is necessary to detect early kidney damage, as dipstick may miss microalbuminuria 2
• Do not skip baseline testing before medication initiation: Baseline electrolytes and kidney function are essential for monitoring medication side effects, particularly with diuretics and RAS blockers 1, 3
• Do not overlook orthostatic blood pressure measurement: Especially important in older adults to detect orthostatic hypotension before treatment 1
• Do not ignore trace or 1+ protein on dipstick: These findings require follow-up quantitative testing with albumin-to-creatinine ratio 5

Evidence Supporting Baseline Testing

A 2025 multicenter study demonstrated that complete baseline laboratory workup in newly diagnosed hypertensive patients resulted in significantly better blood pressure control at 12 months (129.9 vs 142.8 mmHg systolic, p=0.003) compared to partial or no workup 6. The testing unmasked important comorbidities: 8.4% had undiagnosed diabetes, 54.2% had elevated LDL cholesterol, and 7.5% had chronic kidney disease with eGFR <60 mL/min/1.73m² 6.