14 Most Commonly Ordered Lab Tests For Nurse Practitioners

Every day, nurse practitioners make critical decisions guided by lab test results that can significantly impact patient outcomes and treatment plans. These diagnostic tools are the foundation for accurate diagnosis, treatment monitoring, and preventive care strategies.

Understanding the most commonly ordered lab tests is vital for nurse practitioners at all experience levels. Laboratory findings influence clinical decisions, making lab test proficiency an essential skill in modern healthcare practice. 

This guide explores the 14 most frequently ordered lab tests by nurse practitioners, providing practical insights to enhance clinical practice with an evidence-based, patient-centered approach.

The importance of lab tests in nurse practitioner practice

Laboratory testing is a cornerstone of clinical decision-making, providing objective data guiding diagnosis, treatment selection, and monitoring.

Role of lab testing in primary care

Lab tests provide objective measurements that complement the clinical picture, helping nurse practitioners distinguish between similar conditions and confirm suspected diagnoses. 

Regular screening tests also facilitate early disease detection, often before symptoms appear, enabling more effective interventions and improved patient outcomes. 

In primary care settings, appropriate test selection balances diagnostic thoroughness with cost-effectiveness and patient comfort.

How lab results guide diagnosis and treatment

Lab results offer critical information that helps nurse practitioners develop and modify treatment plans based on objective data rather than symptoms alone. 

These tests establish baseline measurements before initiating treatments, monitor therapeutic responses, and detect potential medication side effects. Integrating lab findings with clinical observations, patient history, and evidence-based guidelines creates a comprehensive approach to patient care that improves accuracy and effectiveness.

Legal and ethical considerations when ordering labs

Nurse practitioners must practice within their state-defined scope of practice regarding lab test ordering and interpretation. This includes understanding collaborative agreement requirements, documentation standards, and follow-up protocols. 

Ethical considerations include ordering only clinically necessary tests, ensuring informed consent, maintaining confidentiality, and addressing incidental findings appropriately. 

These legal and ethical frameworks protect patients and providers while promoting high-quality care.

The link between lab results and evidence-based care

Evidence-based guidelines often incorporate specific lab parameters such as diagnostic criteria, treatment thresholds, or monitoring benchmarks. Following these guidelines helps standardize care while allowing for personalization based on individual patient factors. 

Regular updates to clinical guidelines may change recommended testing frequencies, interpretation standards, or decision thresholds, requiring nurse practitioners to stay current with evolving evidence.

Top 14 most commonly ordered lab tests by nurse practitioners

Understanding the clinical applications and interpretation of these frequently ordered tests forms the foundation of effective diagnostic and treatment decisions.

1. Complete blood count (CBC)

The CBC evaluates blood composition through key parameters, including:

• White blood cells (screens for infection and inflammation)
• Red blood cells (screens for oxygen-carrying capacity)
• Hemoglobin (screens for anemia)
• Hematocrit (screens for hydration status)
• Platelets (screens for clotting function)

Clinical applications include diagnosing various types of anemia, detecting infections, evaluating bleeding disorders, monitoring bone marrow function, establishing baselines before procedures, and tracking responses to treatments such as antibiotics or nutritional interventions. 

Abnormal results should be correlated with patient symptoms and may indicate the need for additional, more specific testing.

2. Basic metabolic panel (BMP)

The BMP evaluates essential electrolytes, kidney function, and glucose levels through eight components: 

• Sodium
• Potassium
• Chloride
• Bicarbonate (CO₂)
• Blood urea nitrogen (BUN)
• Creatinine
• Glucose
• Calcium

This panel helps identify electrolyte imbalances that may cause cardiac arrhythmias or neurological symptoms, assesses kidney function (particularly important when prescribing medications eliminated through renal pathways), and monitors chronic conditions like hypertension, heart failure, and diabetes. 

The BMP is valuable for evaluating acute presentations such as dehydration, vomiting, and altered mental status, making it one of the most frequently ordered tests in both inpatient and outpatient settings.

3. Comprehensive metabolic panel (CMP)

The CMP expands on the BMP by adding liver function tests and protein measurements, including: 

• Albumin
• Total protein
• Alkaline phosphatase
• Alanine aminotransferase (ALT)
• Aspartate aminotransferase (AST)
• Bilirubin

This more extensive panel provides a broader assessment of metabolic function, helping detect liver disorders, monitor medication effects on hepatic function, and assess nutritional status. 

The CMP is particularly valuable when evaluating undifferentiated symptoms, screening for undiagnosed conditions, or monitoring patients with multiple chronic diseases affecting metabolic processes.

4. Lipid panel

The lipid panel assesses cardiovascular risk by measuring:

• Total cholesterol
• Low-density lipoprotein (LDL)
• High-density lipoprotein (HDL)
• Triglycerides

Clinical applications include screening for dyslipidemia, evaluating cardiovascular risk, establishing treatment goals, and monitoring responses to lifestyle modifications and lipid-lowering medications. 

Current guidelines emphasize individualized risk assessment rather than fixed targets, considering factors such as age, gender, comorbidities, and overall cardiovascular risk profile to guide testing frequency and treatment decisions.

5. Hemoglobin A1c (HbA1c)

HbA1c measures average blood glucose levels over the previous two—three months, providing insight into long-term glycemic control that point-in-time glucose measurements can’t offer. 

The test is used for diabetes screening, diagnosis (values ≥6.5% indicate diabetes), monitoring treatment effectiveness, and guiding therapy adjustments. 

HbA1c targets typically range from <7% to <8% depending on patient factors such as age, comorbidities, and hypoglycemia risk, with monitoring usually recommended every three—six months to assess treatment adherence and efficacy in preventing diabetes-related complications.

6. Thyroid function tests (TSH, Free T4, Free T3)

Thyroid function tests evaluate this essential metabolic regulator. Thyroid-stimulating hormone (TSH) typically serves as the initial screening test, followed by free thyroxine (T4) and sometimes triiodothyronine (T3) when abnormalities are detected. 

These tests help diagnose hypothyroidism, hyperthyroidism, and subclinical thyroid disorders, monitor response to thyroid medication, adjust dosing, and evaluate thyroid nodules or goiter. 

Interpretation requires understanding the negative feedback relationship between TSH and thyroid hormones—elevated TSH typically indicates hypothyroidism, while suppressed TSH suggests hyperthyroidism.

7. Urinalysis

Urinalysis examines the physical, chemical, and microscopic properties of urine, including color, clarity, specific gravity, pH, glucose, protein, ketones, blood, leukocyte esterase, nitrites, and microscopic elements such as cells, casts, and crystals. 

This versatile test screens for urinary tract infections, kidney disorders, diabetes, liver disease, and metabolic conditions, providing valuable information during pregnancy, preoperative evaluations, and routine health assessments. 

Results should be interpreted considering collection method, timing, hydration status, medications, and menstruation (in females), which can all affect findings.

8. Liver function tests (LFTs)

Liver function tests assess hepatic health by measuring enzymes (ALT, AST, alkaline phosphatase, gamma-glutamyl transferase (GGT)), proteins (albumin, total protein), and metabolic products (bilirubin). 

These tests help diagnose liver disorders, monitor medication effects on hepatic function, screen for alcohol-related liver damage, and evaluate jaundice or abnormal liver imaging findings. 

Pattern recognition is essential in interpretation. Elevated aminotransferases suggest hepatocellular injury, while increased alkaline phosphatase and GGT indicate cholestatic disorders. The timing and magnitude of abnormalities provide insights into acute versus chronic conditions and disease severity.

9. Vitamin D levels

Vitamin D testing measures 25-hydroxyvitamin D, the main circulating form used to assess vitamin D status. Deficiency is associated with bone disorders, increased fall risk, and potentially other chronic conditions. 

This test helps diagnose and monitor the treatment of vitamin D deficiency, especially in at-risk populations such as older adults, those with limited sun exposure, individuals with malabsorption, and patients with osteoporosis or fractures. 

While not recommended for universal screening, targeted testing in high-risk groups can guide supplementation strategies to maintain optimal levels, generally considered above 30 ng/mL for most adults.

10. C-reactive protein (CRP) and high-sensitivity CRP (hs-CRP)

CRP is an acute-phase protein produced by the liver in response to inflammation. Standard CRP measures moderate to high levels associated with infection or inflammatory conditions, while hs-CRP detects lower levels relevant to cardiovascular risk assessment. 

Clinical applications include monitoring inflammatory diseases, detecting infections, assessing cardiovascular risk (particularly with hs-CRP), and guiding antibiotic therapy decisions. 

Interpretation should consider that CRP is a non-specific marker—elevated levels indicate inflammation but not its cause, necessitating clinical correlation and sometimes additional testing.

11. Prostate-specific antigen (PSA)

PSA testing measures a protein produced by the prostate gland that may be elevated in prostate cancer, benign prostatic hyperplasia (BPH), prostatitis, or after prostate manipulation. 

Current guidelines recommend informed decision-making rather than routine screening, with testing generally considered for men aged 55—69 years based on individual risk factors and preferences. 

Interpretation considers total PSA levels, PSA velocity (rate of change over time), free-to-total PSA ratio, and age-adjusted reference ranges, with elevated results, typically prompting urological referral for further evaluation.

12. Partial thromboplastin time (PTT)

The aPTT evaluates the intrinsic and common coagulation pathways, measuring the time it takes for blood to clot after adding activating agents. 

Primary applications include:

• Monitoring unfractionated heparin therapy
• Screening for coagulation factor deficiencies (except Factor VII and Factor XIII)
• Evaluating unexplained bleeding or clotting disorders
• Preoperative screening in patients with a bleeding history or on anticoagulants

Prolonged aPTT may indicate coagulation factor deficiencies, liver disease, disseminated intravascular coagulation (DIC), or the presence of inhibitors such as lupus anticoagulant. 

When healthcare providers refer to “PTT” today, they’re typically referring to the activated version (aPTT).

13. Arterial blood gas (ABG)

ABG analysis measures blood pH, partial pressures of oxygen (PaO₂) and carbon dioxide (PaCO₂), bicarbonate (HCO₃⁻), and oxygen saturation to evaluate respiratory and metabolic acid-base status. 

This test is essential for managing critically ill patients, assessing respiratory function, diagnosing acid-base disorders, guiding oxygen therapy and ventilator management, and monitoring treatment response in conditions like chronic obstructive pulmonary disease (COPD), asthma, pneumonia, and metabolic acidosis or alkalosis. 

Interpretation follows a systematic approach to identifying primary disorders and compensatory mechanisms, helping distinguish between respiratory and metabolic causes of acid-base imbalances.

14. Red blood cell indices (MCV, MCH, MCHC)

Red blood cell indices—mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC)—provide insights into red cell size and hemoglobin content, essential for classifying types of anemia. 

MCV categorizes anemias as:

• Microcytic (small cells), often seen in iron deficiency
• Normocytic (normal-sized cells), often seen in chronic disease
• Macrocytic (large cells), associated with B12/folate deficiency

MCH and MCHC further characterize hemoglobin content and concentration. 

These indices guide diagnostic workup and treatment approaches. Patterns of abnormality suggest specific causes that can be confirmed with additional testing, such as iron studies, B12 levels, or hemoglobin electrophoresis.

Factors influencing lab test ordering patterns

Several factors affect which tests nurse practitioners order and how frequently they’re utilized in clinical practice.

Patient demographics, chronic conditions, and age

Patient characteristics significantly influence lab test selection and frequency, with age-related reference ranges and screening recommendations varying across the lifespan. 

Chronic conditions often require specific monitoring panels—diabetes necessitates regular HbA1c and renal function tests, while cardiac conditions may warrant more frequent lipid panels and electrolyte monitoring. 

Understanding how demographic factors affect test results and interpretation is vital for accurate clinical decision-making and personalized care planning.

Legal scope of practice and collaborative agreements

State regulations and collaborative practice agreements may impact nurse practitioners’ autonomy in ordering and interpreting certain laboratory tests. 

These legal frameworks vary significantly by state, with some allowing independent practice and others requiring physician supervision or collaboration. Nurse practitioners should understand their state’s specific requirements regarding lab test ordering, result interpretation, and follow-up responsibilities to ensure compliant practice while efficiently meeting patient needs.

Accessibility of lab facilities and insurance coverage

Practical considerations like laboratory accessibility, insurance coverage, and patient financial constraints often influence test selection and frequency. 

Rural or underserved areas may have limited access to specialized testing, necessitating strategic test ordering and patient referrals. 

Insurance coverage varies widely, with some plans limiting specific tests or requiring prior authorization, particularly for specialty or genetic testing. 

Understanding these practical barriers helps nurse practitioners develop realistic testing strategies that balance clinical needs with patient resources.

Evidence-based clinical guidelines and protocols

Professional organizations and specialty societies publish evidence-based guidelines for appropriate test selection, frequency, and interpretation. 

These recommendations are based on research evidence, expert consensus, and cost-effectiveness analyses, providing standardized approaches to common clinical scenarios. 

Staying current with evolving guidelines ensures that nurse practitioners’ testing practices reflect the latest scientific understanding while aligning with accepted standards of care.

Best practices for interpreting and communicating lab results

Effective interpretation and communication of lab results are essential skills that impact patient understanding and treatment adherence.

Contextual and holistic interpretation of lab data

Lab results should never be interpreted in isolation but considered within the context of the patient’s clinical presentation, medical history, current medications, and other relevant factors. 

A holistic approach considers patterns across multiple tests, trends over time, and the significance of even subtle variations within reference ranges.

For an additional resource to help you get started, check out Fullscript’s provider’s guide to optimal biomarker ranges. 

This guide, developed by the Fullscript Medical Advisory Team, utilizes medical research and advanced technology to refine optimal ranges through large datasets from trusted sources like ScienceDirect and PubMeb. 

Download the guide

Patient-centered communication strategies

Communicating lab results effectively requires adapting language and detail level to each patient’s health literacy, emotional state, and information preferences. 

Key strategies include using plain language, explaining the significance of results rather than just the numbers, connecting findings to symptoms or concerns, and providing written summaries for reference. 

Visual aids such as graphs showing trends over time or simplified ranges can enhance understanding, particularly for patients monitoring chronic conditions through regular testing.

Ethical disclosure and shared decision-making

Test result disclosure should follow ethical principles of transparency while considering timing, setting, and patient readiness for information. 

Abnormal results requiring significant intervention or indicating severe conditions may warrant in-person discussion rather than electronic or phone communication. 

Shared decision-making involves educating patients about the implications of their results, presenting evidence-based management options, and respecting patient preferences and values when developing treatment plans based on laboratory findings.

Overcoming common challenges in lab testing

Nurse practitioners regularly encounter several key challenges related to lab testing that require strategic approaches to ensure optimal patient care. 

These include managing slightly abnormal or borderline results through baseline comparison and trend analysis, addressing pre-analytical variables, and determining appropriate follow-up actions such as watchful waiting or additional testing. 

Many patients also experience test-related anxiety, which nurse practitioners can mitigate by providing clear pre-test information, explaining the purpose of tests, setting realistic timelines for results, and implementing supportive follow-up procedures for those with severe concerns.

Establishing systematic approaches to test follow-up represents another critical challenge. This requires designated staff responsibilities, standardized documentation, patient reminders, and mechanisms to flag overdue testing. 

Patient engagement through shared goal-setting and technology can significantly improve monitoring compliance. 

For nurse practitioners in rural or underserved areas, resource limitations present additional obstacles that can be addressed through:

• Point-of-care testing
• Relationships with reference laboratories
• Scheduled lab days
• Mobile health units
• Telehealth consultations for complex result interpretation
• Patient assistance programs to overcome financial barriers to necessary testing

Frequently asked questions (FAQs)

Consider the following frequently asked questions about lab testing ordered by nurse practitioners.

What are the most essential lab tests nurse practitioners should know? 

The most essential tests include CBC, BMP/CMP, lipid panel, HbA1c, thyroid function tests, and urinalysis. These provide fundamental information about overall health status, metabolic function, and common disease processes for preventive care and diagnostic evaluation.

How often should common lab tests be ordered for patients? 

Testing frequency depends on individual patient factors, underlying conditions, medications, and evidence-based guidelines. Healthy adults might need screening every 1-3 years, while patients with chronic conditions typically require monitoring every 1-6 months based on clinical stability.

Can nurse practitioners order all types of lab tests? 

Ordering authority varies by state practice regulations and collaborative agreements. Most states allow nurse practitioners to order routine diagnostic tests, while some may restrict specific specialized or genetic tests.

How do nurse practitioners interpret slightly abnormal lab results? 

Interpretation involves considering the degree of abnormality, trending from previous results, clinical presentation, and potential confounding factors like medications or collection issues. 

Slightly abnormal results often warrant repeat testing before intervention, while persistent patterns may suggest early disease processes requiring further investigation.

What steps should be taken if lab results indicate a serious condition? 

When results suggest a serious condition, nurse practitioners should confirm accuracy, consult physicians or specialists, and ensure timely patient notification with documented follow-up plans. 

Developing an immediate intervention plan with appropriate referrals and precise documentation of all communications protects both patient safety and provider liability.

What legal limitations exist around lab test ordering by nurse practitioners? 

Legal limitations vary by state but may include requirements for physician co-signatures, restrictions on specific test categories, and mandated physician review of abnormal results. 

Facility policies may impose further restrictions beyond state regulations, particularly for high-cost or specialized testing.

How do evidence-based guidelines influence lab test selections? 

Evidence-based guidelines provide standardized recommendations for screening intervals, diagnostic workups, and result interpretation thresholds. 

These guidelines help prevent over-testing while ensuring appropriate detection and monitoring of health conditions, ultimately improving care quality and resource utilization.

What factors should nurse practitioners consider when interpreting lab results in special populations? 

Special populations require adjusted interpretation frameworks, including age-specific reference ranges for pediatric and geriatric patients and physiological adjustments for pregnant women. 

Factors such as ethnicity, chronic conditions, and medications can establish personal baselines that differ from population norms but represent the patient’s optimal health status.

Key takeaways

• Understanding the most commonly ordered lab tests gives nurse practitioners essential knowledge to enhance diagnostic accuracy, improve treatment monitoring, and optimize patient outcomes. 
• By combining clinical expertise with evidence-based interpretation of laboratory data, nurse practitioners can develop comprehensive care plans that address acute and chronic health needs. 
• Effective communication of results using patient-centered strategies ensures that individuals understand the significance of their findings and are motivated to adhere to recommended interventions. 
• As healthcare evolves, nurse practitioners who maintain current knowledge of laboratory testing best practices will be well-positioned to deliver high-quality, cost-effective care that supports optimal health across diverse patient populations.

Disclaimer: This content is for educational purposes only and does not constitute legal or medical advice. Nurse practitioners should consult their state’s specific laws, regulations, and professional licensing boards to determine their individual scope of practice and legal responsibilities. Always seek appropriate legal counsel or institutional guidance when interpreting regulatory requirements.