The 10 Most Commonly Ordered Lab Tests For Medical Doctors

A medical doctor (MD) is a licensed healthcare provider with advanced clinical training. Their education and experience allow them to evaluate symptoms, order lab tests, and guide care using the best available research—while following strict legal and ethical standards.

Blood draws and lab tests are a routine part of medical care. According to the American Clinical Laboratory Association (ACLA), more than 14 million lab tests are performed each year in the United States. These tests form a core part of both ongoing health monitoring and early detection efforts.

For doctors, understanding lab testing is important—not only to help identify possible concerns but also to track changes over time and support treatment planning. 

This guide offers a well-organized reference to some of the most commonly ordered lab tests, grouped by their clinical purpose. Understanding how these tests work can help support more informed decisions and proactive care.

Top 10 Commonly Ordered Lab Tests

Here are the top 10 most commonly ordered lab tests that MDs order. 

Core Lab Panels in Everyday Medicine

These panels are essential diagnostic tools that can offer valuable insights into a patient’s current health status and can guide both acute and preventative care strategies.

1. Complete Blood Count (CBC)

The CBC is one of the most common laboratory tests in all of medicine. The test counts the number of circulating red blood cells, white blood cells, and platelets, as well as determining their size, concentrations, volumes.

A CBC can be used to help identify possible infection, inflammation, anemia, leukemia, thrombocytopenia, and a host of other issues. 

2. Basic Metabolic Panel (BMP)

The BMP is designed to provide a physician with a basic insight into how the body’s endocrine system and metabolism are functioning.

A BMP will measure electrolytes (sodium, potassium, chloride, carbon dioxide), kidney function (BUN, creatinine), glucose levels, and calcium levels. It’s a blood test that’s designed to give a general insight into a patient’s overall health.

3. Comprehensive Metabolic Panel (CMP)

For a more detailed look, the CMP measures an additional six substances in the blood: liver enzymes alkaline phosphatase (ALP), alanine aminotransferase (ALT) and aspartate aminotransferase (AST), albumin, protein, and bilirubin.

The CMP can allow for better understanding of chronic disease states, monitoring of medication use, and especially liver function.

Disease-Oriented Diagnostic Panels

While blood counts and metabolic panels are useful, there are some blood panels specific to known disease states and are, therefore, also part of the core group of blood tests.

4. Lipid Panel

A lipid panel gives providers a good look not only into the levels of cholesterol and fat within the patient, but also insight into dietary and lifestyle habits as well as treatment guidelines for cholesterol medications.

In the lipid panel, cholesterol is reported in four primary categories and, occasionally, two other categories of:

• Total cholesterol refers to the overall amount of cholesterol in the blood, including both low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol. It’s one of several markers that healthcare providers may use when evaluating cardiovascular health. 
• Low-density lipoproteins (LDLs), often referred to as ‘bad’ cholesterol, carry cholesterol through the bloodstream and can contribute to the buildup of plaque in the arteries. Higher levels of LDL cholesterol are one of several factors that healthcare providers may consider when evaluating a person’s potential risk for cardiovascular conditions such as heart attack (myocardial infarction) and atherosclerosis.
• High-density lipoproteins (HDLs), commonly known as ‘good’ cholesterol, help transport excess cholesterol from the bloodstream to the liver for removal. Lower levels of HDL cholesterol may be one of several factors considered when assessing cardiovascular health. 
• Triglycerides are a type of fat found in the blood that the body uses for energy. Elevated triglyceride levels may be associated with certain cardiovascular risk factors and are often evaluated as part of a broader lipid profile. 
• All non-HDL cholesterol is a more refined tool in determining risk factors for cardiovascular disease and is often seen as a more comprehensive test than just total cholesterol.
• Cholesterol/HDL ratio is a more precise indicator of ischemic heart disease risk, especially in men, as it compares the benefits of HDLs against the risks of LDLs.

5. Thyroid Function Panel

The thyroid function panel is a group of tests that measure the levels of a variety of hormones involved in thyroid function. These tests are particularly good for helping identify and monitoring disorders such as hyperthyroidism and hypothyroidism.

Thyroid function testing includes:

• Thyroid-stimulating hormone (TSH) is produced by the pituitary gland and stimulates the thyroid for the regulation of metabolic processes, and it is one of the best indicators of thyroid disorders.
• Free T3 is often seen as a secondary test that’s best used for the assessment of thyroid replacement therapies.
• Free T4 is best used in conjunction with TSH measurements and can be particularly helpful in diagnosing and managing central hypothyroidism.
• TPO Antibody results are used in the diagnosis of thyroid-affecting autoimmune disorders, especially Hashimoto’s Thyroiditis.

6. Hemoglobin A1c (HbA1c)

For diabetes management, HbA1c is widely used to assess long-term glucose control. HbA1c measures average blood sugar over the previous three months, making it an excellent indicator of diabetic glucose control, and one that only needs to be done once a quarter.

7. Prostate Specific Antigen (PSA)

PSA is a protein produced by both normal and abnormal cells in the prostate gland. The PSA test is a blood test that measures the level of this protein in the bloodstream and may be used by healthcare providers to evaluate prostate health. 

While elevated PSA levels can be associated with conditions such as prostate enlargement, inflammation, or, in some cases, prostate cancer, they aren’t diagnostic on their own. 

The PSA test is often used as part of early detection efforts, especially in individuals with risk factors or a family history of prostate issues. Healthcare providers may also use PSA levels to monitor for changes over time as part of a broader approach to prostate care.

Inflammatory markers

These tests help clinicians detect and monitor inflammation in the body, offering important clues in the diagnosis and management of acute and chronic conditions.

8. C-reactive Protein (CRP)

CRP is a substance produced by the liver in response to inflammation in the body. A CRP test measures the level of this protein in the blood and may be used by healthcare providers to assess the presence and intensity of systemic inflammation. 

Elevated CRP levels aren’t specific to any one condition but can be associated with a range of inflammatory processes, including infections, chronic diseases, or injuries. Because of its broad applicability, CRP testing is commonly used in clinical settings to support the evaluation of immune system activity and overall inflammatory status.

9. Erythrocyte Sedimentation Rate (ESR)

The ESR test measures how quickly red blood cells settle at the bottom of a test tube over a set period of time. It’s often used alongside other tests, such as C-reactive protein (CRP), to help healthcare providers evaluate general levels of inflammation in the body. 

While a high ESR may be associated with a variety of health conditions—including infections, chronic diseases, or autoimmune activity—it’s a nonspecific marker and doesn’t point to a particular diagnosis on its own. Instead, it may be used to support a broader clinical assessment of inflammatory or immune-related concerns. 

Urine Testing

Urine tests provide a non-invasive way to assess kidney function, detect infections, and monitor metabolic and systemic health.

10. Urinalysis

Urinalysis is a foundational diagnostic test that examines the physical, chemical, and microscopic properties of urine. It can detect signs of urinary tract infections (UTIs), kidney disease, diabetes, dehydration, and other metabolic conditions. 

The test typically includes measurements of urine color, clarity, pH, specific gravity, and the presence of substances such as protein, glucose, ketones, blood, leukocyte esterase, and nitrites. Microscopic analysis may also identify crystals, casts, and cells that provide further diagnostic insight.

Best practices in test utilization

When ordering labs, it’s important to ensure the ordered tests match the patient history and current story. Ideally, tests should be used to guide clinical decisions, monitor conditions, and rule out potentially incorrect diagnosis.

If the labs are meant to be part of an annual physical, then broad-based labs such as the CBC and CMP are best. If specific issues are suspected, such as hypothyroidism due to low TSH, then more specific labs are utilized, such as T4 levels.

Providers should ensure they use proper evidence-based labs, using programs such as the American Board of Internal Medicine’s Choosing Wisely® program.

Once test results are available, MDs are encouraged to interpret them within the broader context of the patient’s overall health, medical history, and presenting symptoms. Rather than focusing solely on individual test values, it’s important to consider how the results align with the full clinical picture to support informed and effective care decisions.

Frequently Asked Questions (FAQs)

When should a provider decide between ordering a BMP or CMP? 

The choice between a BMP and a CMP depends on the type and depth of information needed. A BMP includes tests that assess key markers of kidney function, blood sugar, and electrolyte balance. A CMP includes all of these tests plus additional markers related to liver function, such as liver enzymes and proteins. 

Healthcare providers may choose a CMP when they want a more complete picture of metabolic and organ health, particularly when liver function is a clinical consideration.

Which lab tests are most cost-effective in primary care? 

In many primary care settings, the CBC and BMP are frequently considered among the most cost-effective tests. These panels provide broad, useful information about a patient’s overall health—including red and white blood cell levels, electrolyte balance, and kidney function—which can be helpful for routine evaluations and early detection of imbalances.

What are red-flag lab results in a CBC that require urgent referral? 

Certain findings on a CBC may warrant further evaluation by a specialist. For example, significantly elevated white blood cell counts may suggest a serious infection or other immune-related concern. 

Very high or low red blood cell or platelet counts may also raise concern and prompt additional investigation. However, all test results should be interpreted within the context of the patient’s overall clinical picture, and decisions about referral are best made by a qualified healthcare provider.

What causes falsely elevated or depressed lab values? 

Several factors can influence the accuracy of lab results. These include issues with sample collection (such as improper handling or timing), storage conditions, patient preparation (such as fasting status), and certain medications or supplements. 

In some cases, lab variability or equipment limitations may also affect outcomes. If results appear inconsistent with clinical signs or history, a healthcare provider may consider retesting or using additional diagnostic tools.

When should abnormal tests be repeated? 

Repeating a test may be appropriate when results appear out of range but don’t align with the patient’s symptoms or clinical history. For example, a high white blood cell count in an otherwise asymptomatic person may prompt a provider to retest before pursuing further evaluation. 

On the other hand, abnormal results that are consistent with a known condition—such as low iron levels in someone with diagnosed anemia—may not require immediate repeat testing. These decisions should always be made by a healthcare provider based on the individual situation.

Key Takeaways

• Lab tests are valuable tools that can support clinical decision-making by providing insight into various aspects of a patient’s health. When used thoughtfully, they may help guide monitoring and care planning.
• Individual test results should be interpreted within context. Rather than focusing on isolated values, healthcare providers should consider the patient’s full clinical picture, including symptoms, history, and other relevant findings.
• Thoughtful test ordering helps reduce unnecessary costs and confusion. Selecting appropriate labs based on the clinical question at hand can improve care quality and avoid excess or redundant testing.
• Abnormal results don’t always indicate illness. Variations can result from temporary changes, lab error, or physiological differences. When results appear unexpected or inconsistent, retesting or further evaluation may be needed.
• Laboratory data is only one piece of the puzzle. While lab results can offer important insights, they work best as part of a comprehensive care strategy that includes physical exams, patient history, and clinical judgment.
• Ongoing review of lab ordering practices can help healthcare providers stay current with best practices and ensure that tests are being used effectively and appropriately.

This article is for educational purposes only and is not intended to substitute for professional medical advice, diagnosis, or treatment.