What are the recommended baseline labs, including urine tests, for a patient with newly diagnosed hypertension?

Baseline Laboratory Tests for Newly Diagnosed Hypertension

All patients with newly diagnosed hypertension should undergo a standardized panel of basic laboratory tests including serum creatinine with eGFR, electrolytes (sodium, potassium, calcium), fasting blood glucose, lipid profile, thyroid-stimulating hormone, complete blood count, urinalysis, and urinary albumin-to-creatinine ratio, along with a 12-lead electrocardiogram. 1

Essential Blood Tests

The following blood tests are mandatory for all newly diagnosed hypertensive patients:

• Serum creatinine with estimated glomerular filtration rate (eGFR) to assess baseline kidney function and identify chronic kidney disease 1
• Serum electrolytes including sodium, potassium, and calcium to screen for secondary causes (particularly primary aldosteronism if hypokalemia is present) and establish baseline values before starting diuretics or RAS blockers 1, 2
• Fasting blood glucose to identify diabetes, which significantly increases cardiovascular risk and influences treatment decisions 1, 3
• Lipid profile (total cholesterol, LDL, HDL, triglycerides) to assess cardiovascular risk and guide statin therapy decisions 1, 2
• Thyroid-stimulating hormone (TSH) to exclude thyroid dysfunction as a secondary cause of hypertension 1, 2
• Complete blood count to establish baseline hematologic parameters 1

Essential Urine Tests

Urinary albumin-to-creatinine ratio (UACR) is the preferred test over urine dipstick alone because it detects earlier kidney damage (albuminuria 30-300 mg/g) that indicates end-organ damage from hypertension and heightened cardiovascular risk. 1 The 2024 ESC guidelines specifically recommend measuring urine albumin-to-creatinine ratio in all patients with hypertension. 1

• Urinalysis provides basic screening for hematuria, proteinuria, and urinary tract abnormalities 1
• Urinary albumin-to-creatinine ratio is superior to dipstick for detecting microalbuminuria and should be the standard test 1, 2

Electrocardiogram

A 12-lead ECG is mandatory for all patients with newly diagnosed hypertension to detect left ventricular hypertrophy, atrial fibrillation, and ischemic heart disease. 1, 2

Optional Tests Based on Clinical Context

The following tests should be ordered when specific clinical features suggest target organ damage or secondary causes:

• Echocardiogram when ECG shows abnormalities, cardiac murmurs are present, or cardiac symptoms exist 1, 2
• Hemoglobin A1c provides additional diabetes screening, particularly useful when fasting glucose is borderline 1, 3
• Uric acid may be considered but is optional 1
• Liver function tests are recommended by ESC guidelines 1, 2

Clinical Rationale for Testing

These laboratory tests serve three critical purposes:

First, they identify target organ damage including kidney dysfunction (elevated creatinine, reduced eGFR, albuminuria), which affects treatment choices and prognosis. 1, 2 Studies show that 35.5% of newly diagnosed hypertensive patients have elevated creatinine and 7.5% have eGFR <60 mL/min/1.73m². 3

Second, they screen for secondary causes of hypertension. Hypokalemia suggests primary aldosteronism (affecting 8-20% of resistant hypertension cases), while abnormal TSH indicates thyroid dysfunction. 1, 2, 4 The 2024 ESC guidelines now recommend measuring renin and aldosterone in all adults with confirmed hypertension, representing a significant shift toward broader screening. 4

Third, they establish baseline values before initiating medications. This is essential for monitoring medication side effects, particularly with diuretics (which can cause hypokalemia) and RAS blockers (which can affect kidney function and potassium levels). 1, 2

Impact on Clinical Outcomes

Patients who receive complete baseline laboratory workup achieve significantly better blood pressure control compared to those with partial or no testing. 3 In one study, patients with complete workup had systolic blood pressure of 129.9 mmHg at 12 months versus 142.8 mmHg in the partial workup group (P = 0.003). 3

Baseline testing frequently uncovers important comorbidities: 8.4% have undiagnosed diabetes (fasting glucose >125 mg/dL), 54.2% have elevated LDL cholesterol requiring statin therapy, and 7.5% have significant kidney disease (eGFR <60). 3, 5

Common Pitfalls to Avoid

Do not rely on urine dipstick alone for kidney assessment—it misses microalbuminuria, an early marker of hypertensive kidney damage and cardiovascular risk. 1 The KDOQI guidelines specifically recommend UACR over dipstick for screening. 1

Do not stage hypertension based on a single blood pressure measurement. Despite guidelines recommending multiple measurements, 85% of patients in practice studies had hypertension staged on a single reading. 6

Do not skip baseline testing before starting medications. Without baseline electrolytes and kidney function, you cannot safely monitor for medication side effects or detect deterioration. 2, 7

Do not order expensive imaging studies before completing basic laboratory screening. The systematic approach starts with blood and urine tests, reserving imaging for patients with specific clinical clues suggesting secondary causes. 4