Lab Test Results Explained: Your Complete Beginner’s Guide to Reading Blood Work

Learn how to read and understand your lab test results with this comprehensive guide. Decode CBC, lipid panels, and more medical tests easily.

Introduction

Your blood work is a detailed analysis of what is going on in your body at this moment. It reveals how well your organs are functioning or if you are potentially at risk of developing any disorders. According to the Centers for Disease Control and Prevention (CDC) 70% of healthcare decisions depend on laboratory tests [4]. Physicians use a single latest blood work or a series of past blood work to observe the trend in your results to diagnose or choose an appropriate treatment for you. Hence, it is important for you to understand them in order to make appropriate healthcare decisions.

As a medical professional, I regularly receive lab results from almost all of my family members seeking help for interpretation. During my clerkships at hospitals, I noticed that 80% of the patients who received their lab results automatically through hospital apps feel completely lost! The medical terminology often leaves them confused and anxious about their health. I will walk you through it step by step on how to read these common test results such as complete blood count (CBC), comprehensive metabolic panel (CMP), lipid panel, thyroid function tests, and more.

If you’ve just received your results that look like a foreign language or are a medical professional looking to strengthen your interpretation skills, this guide will help you decode these lab results which many feel like an alien code. By the end of this guide, you will be an expert in reading laboratory reports.

Let’s get started and understand these numbers together.

Understanding Laboratory tests and why do they matter?

Laboratory tests check a sample of your blood, urine, or body tissues. A lab technician analyzes the test samples to see if your results are within the normal range. A reference range is used because what is normal differs from person to person [1].

Why are lab tests ordered?

Lab tests are ordered by your physician for 3 main purposes: Screening, diagnostic and prognosis.

1. Screening tests: these are primarily used for early detection of disease or risk factors.

2. Diagnostic tests: used to establish the presence or absence of disease.

3. Prognostic tests: monitor trend in your results to determine if your medications are effective, if you’re overdosed, or to monitor your condition.

These allow physicians to tailor treatment plans to improve your health outcomes.

Multiple research studies have provided strong evidence for the preventive power of routine blood tests. A long-term clinical trials has shown that a 10% reduction in serum cholesterol resulted in a 30% reduction in coronary events [2]. This has the potential for greatly reducing coronary heart disease (CHD), which still remains the number 1 killer in the United States [2]. Similarly another study conducted at 23 hospital-based clinics in England, Scotland, and Northern Ireland, on diabetic patients showed that every 1% reduction in HbA1c level (a measure of long-term blood sugar control) was associated with 21% reduction on deaths, 14% reduction in myocardial infraction (heart attack) and 37% reduction in microvascular complications such as eye, kidney and nerve diseases that are commonly associated with diabetes [3].

Know your legal rights…

Every patient has the right to access and understand their health information including medical records and test results. This right is protected by the laws like HIPPA [5]. The U.S. Department of Health and Human Services (HHS) issued a final rule in 2014 that allows patients or their representatives direct access to laboratory test reports after having their identities verified, without the need to have the tests sent to a health practitioner first. Hence you can request your results and records to understand your health. This is for:

1. Empowerment: to make informed health decisions

2. Communication: to improve communication between health care providers and patients.

3. Better health outcomes: active involvement of patient in their care results in better prognosis.

4. Mental health: by understanding their results it reduces anxiety and enhances control over their health in patients.

5. Trust: transparent communication of information builds trust between patients and physicians.

How to Read Your Lab Report: The Basics

Now that you know what are these lab tests and why they are important, let’s learn how to read them.

Let’s understand the layout of your lab report…

Sample Lab Reports

I found some lab reports online for your reference:

Note: the below reports are not referring to an actual person and are found on google images.

You will find the following at the top of your report:

1. Patient Information: patient's name, date of birth, contact, etc.

2. Physician Information

3. Laboratory Information: Name and address of the testing laboratory.

4. Date and time the sample was registered, collected, received and reported.

You might find other information which you don’t need to worry about.

Test Results:

Lab tests are grouped into categories like:

1. Complete Blood Count (CBC)

2. Basic/Comprehensive Metabolic Panel (BMP/CMP)

3. Lipid Panel

4. Specific Tests like thyroid panel, hormone levels, B12 levels, Vitamin D levels, and more

In each category you will find:

1. Name of the specific blood test component

2. Result: a numerical value and/ or “high, low or normal”

3. Units: mg/dL, cells/uL, mmol/L, etc

4. Reference Range: normal range of values for the test

5. Flags: result is printed in bold or red, marketed with “</ low“, “>/ high“, "*" if the result is outside the reference range.

The following sections are found in some reports

Clinical Comments:

Here the physician provides additional comments regarding the purpose of the test. The comments explain what it means if the results are outside the reference range and the potential implication on the patient’s health. It may also suggest follow up tests and consultations if required.

Summary:

This section provides a brief overview of the key findings and highlights the critical values or trends compared to your previous tests if available.

Why reference ranges can vary between labs?

You might notice that results from different labs have different reference ranges, this causes dilemma in many people. However, you just need to follow the reference noted on your report.

Labs establish their reference ranges by testing large groups of healthy people to determine a “normal” range for that group. The variation between reference ranges in different labs is because of the following:

1. Method of assessment used.

2. The health of the population in the area where the reference ranges were established.

3. Reflects what is typical based on age, gender, and other factors in the chosen population by the lab or the area.

4. Different standard deviation from the mean used in their sample set.

5. Different analytical methodologies, testing equipment, or reagents.

6. A lab may also cite references established by test manufacturers.

Red flags vs. minor variations in results

A normal lab result doesn’t always mean all is well. An abnormal one doesn’t always mean trouble either.

Understanding reference ranges

Reference ranges show where 95% of healthy people fall. That means 5 percent of healthy folks will have results outside the range. So if you see an “H” or “L” on your report, don’t assume the worst.

Normal Isn’t Always Reassuring

Likewise some values can look fine on paper but still raise concern when viewed over time. For example, your cholesterol might be in range but creeping upward from your previous normal result, implies early cardiovascular risk.

This is why doctors don’t just scan for flags. They watch patterns. A glucose level that is normal but has increased 20 points over 2 years indicates that you are developing insulin resistance, even though your result is within the reference range.

One number sometimes don’t tell us the whole story, patterns do. Regular checkups and personal records will help you spot issues early—before they become something you can’t ignore. Catching disease early is great. Avoiding it altogether is better!

Minor Variations That Usually Aren't Concerning

Small deviations from normal ranges often reflect temporary changes or individual variations:

1. Low HDL, can be improved with exercise.

2. Total cholesterol is high but you have good HDL, it is not worrying.

3. Glucose slightly high means pre diabetic which can be managed with lifestyle changes.

4. Slightly elevated liver enzymes can be due to ongoing medications or alcohol consumption.

5. Low vitamin levels are often corrected with diet.

The point is, labs aren’t always an emergency. They’re part of a bigger picture.

Critical values that need immediate care

Most abnormal results can wait for a routine follow-up. However, some values are considered medical emergencies that require immediate care. I’ve created a reference table of these “critical” or “panic” values using reputable websites like lab corp and main line health.

You can download the table from the link below:

https://drive.google.com/file/d/1i_raJwO1EW37MN_-e98VkP9G_dnoVxzC/view?usp=sharing

* If you have critical values, your doctor will usually call you immediately, sometimes even before your lab results are posted to your patient portal.*

What to do after getting you results?

Understanding your lab results is just the first step. Here's how to make the most out of your results.

Prepare questions for your provider…

Patients frequently attend lab result appointments without any preparation and walk away confused about why their treatment changed, why they're starting new medications, and what to expect going forward.

Look over your results, flag what stands out, and come in ready.

If something’s off:

1. What’s likely causing this?

2. How urgent is it?

3. What are my options to fix it?

4. How will we track it going forward?

If everything looks fine:

1. Is anything changing in a way that could be a problem later?

2. Should I be doing anything now to prevent issues down the line?

3. When should I repeat these tests?

For context:

1. How do I compare to others my age and sex?

2. Could any lifestyle habits be messing with these numbers?

3. Are my meds or supplements skewing anything?

Clear questions lead to clear answers. Don’t waste the visit.

Using Patient Portals Effectively

Most hospitals/clinic are now offering patient portals where you can access your results online.

Here's how to use them effectively:

1. Set up notifications to alert you when new results are posted

2. Review your results and using the information we learnt above

3. Use the messaging, video call, and/or phone call feature if you have any questions about your results.

4. Print or save important results for your records.

5. Schedule your next follow-up appointments with your provider.

6. Fill out pre-visit forms online, if available. This will help you save time during your visit.

Keeping Track of Your Lab History

Maintaining your own records isn’t just helpful but also smart.

1. Use a simple spreadsheet to log key values—cholesterol, blood sugar, blood pressure. Track how they change over time.

2. Add context when it matters. If you were sick, started a new med, or went on a weekend party, make a note

3. Bring your records to appointments. It saves time and helps your doctor see patterns faster.

4. When you switch providers, showing up with your own lab history provides valuable data.

What’s Coming Up in the Lab Results Series?

Now that you’ve got the basics of reading lab reports, it’s time to understand the major tests you’ll actually see on your reports.

Next up:

1. Complete Blood Count (CBC) Results: Understanding your WBC, RBC, hemoglobin, platelets, and more.

2. Metabolic Panel Interpretation: for kidney function, liver health, blood sugar levels, etc.

3. Lipid Panel Breakdown: for cholesterol

4. Specialized Tests: Thyroid function, inflammation markers, and hormone levels

Each post will build on what you already know, giving you knowledge to understand any blood test result. Save this guide, use it as your go to resource to understand those test results and share it to family and friends who always texts you their labs.

Subscribe to get notified when the next post in this series is published, and never miss important health insights that could change your life.

Disclaimer note for the readers…

This content is for educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition, treatment options, or health concerns. See our full medical disclaimer: https://nikithagovula.substack.com/about#§medical-disclaimer

References

1. MedlinePlus. Last updated 2017, December 13. Laboratory tests. U.S. National Library of Medicine. https://medlineplus.gov/laboratorytests.html

2. Cohen JD. A population-based approach to cholesterol control. Am J Med. 1997 Feb 17;102(2A):23-5. doi: 10.1016/s0002-9343(97)00463-4. PMID: 9217582.

3. Stratton I M, Adler A I, Neil H A W, Matthews D R, Manley S E, Cull C A et al. Association of glycaemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study BMJ 2000; 321 :405 doi:10.1136/bmj.321.7258.405

4. Centers for Medicare & Medicaid Services. (2023, January 18). FDA and CMS statement: Americans deserve accurate and reliable diagnostic tests, wherever they are made. Pre release Press Release. U.S. Department of Health & Human Services. https://www.cms.gov/newsroom/press‑releases/fda‑and‑cms‑statement‑americans‑deserve‑accurate‑and‑reliable‑diagnostic‑tests‑wherever‑they‑are‑made

5. Individuals’ Right under HIPAA to Access their Health Information. 45 CFR Sec 164.524 https://www.hhs.gov/hipaa/for-professionals/privacy/guidance/access/index.html#newlyreleasedfaqs

6. Testing.com. (2021, January 27). Deciphering your lab report. Testing.com. https://www.testing.com/articles/how-to-read-your-laboratory-report/

7. Labcorp. (n.d.). Critical values. Labcorp. https://www.labcorp.com/test-menu/resources/critical-values

8. Main Line Health. (n.d.). Services for health care professionals: Critical values. Main Line Health. https://www.mainlinehealth.org/specialties/labs-and-pathology/services-for-health-care-professionals/critical-values

9. Optimal DX. (n.d.). Why labs offer different standard reference ranges. Optimal DX. https://www.optimaldx.com/research-blog/why-labs-offer-different-standard-reference-ranges

10. Sanderson, V. (2023, May 1). Understanding lab reference ranges: A primer. NP Reasoning. https://www.npreasoning.com/lab-test-interpretation/understanding-lab-reference-ranges-a-primer