Understanding Common Blood Tests and What They Mean (2023)

If you're having surgery—even a minor procedure—the doctor may order blood tests. While interpreting blood tests are best left to a physician, it may be helpful to understand what the test is looking for, and what's considered a "normal" result.

There are hundreds of different blood tests that can be performed in a lab, but the most common are performed routinely before and after surgery; these tests are very common and should not be cause for alarm.

The providerwants to make sure the patient is in the best possible health for the procedure and to diagnose any conditions that could cause preventable complications. Blood testing is also often done after a procedure to look for bleeding, and to make sure that the organs are functioning well after surgery.

Many times these tests are performed routinely, often the night after surgery. This does not mean that there is an expectation that something is wrong, most often these tests confirm that everything is going well after surgery.

Patients in the ICU can expect to have more frequent blood tests.If you are on a ventilator you can expect an arterial blood gas to be drawn daily or even more often.

Understanding Common Blood Tests and What They Mean (1)

Chem 7

Also known as a blood chemistry, chemistry panel, or basic metabolic panel, this test looks at the levels of essential enzymes in the blood and also checks kidney function. In addition, the glucose level in the blood is obtained through this test and can indicate if a person needs furthertesting for diabetes.

The seven tests included are:

  • Blood urea nitrogen (BUN)
  • Serum glucose
  • Creatinine
  • Carbon dioxide (CO2)
  • Serum chloride
  • Serum sodium
  • Serum potassium

Chem 7 Blood Chemistry Tests: Basic Metabolic Panel

CBC

A complete blood count (CBC), looks at the different cells that make up whole blood. A CBC can inform the doctor if the body is making the appropriate number of each type of cell, and it can also reflect signs of a current or recent infection, bleeding, or clotting issues.

After surgery, the doctor may order this test to see if a blood transfusion is warranted, or to evaluate for infection.

A CBC includes:

  • White blood cell count (WBC)
  • Red blood cell count (RBC)
  • Platelet count (Plt)
  • Hemoglobin
  • Hematocrit

An H&H is similar to a CBC but only looks at the hemoglobin and hematocrit levels.

What Your CBC Blood Test Results Say About Your Health

(Video) Lab Results, Values, and Interpretation (CBC, BMP, CMP, LFT)

PT, PTT, and INR

These tests, known collectively as a coagulation panel, looks at the ability for your blood to clot. Disordered clotting ability can cause problems in surgery, during which bleeding is often expected.

If the result show impaired clotting ability, it may be necessary to delay surgery to prevent significant bleeding during the procedure. This test may also be used to monitor blood-thinning medications, such as Coumadin (warfarin).

Liver Enzymes

Liver function studies, also known as LFTs, are done to determine if the liver is functioning normally. Because the liver plays a role in removing anesthesia from the bloodstream and normal blood clotting, it's essential to know if it's functioning normally prior to the procedure. Elevated numbers can indicate liver damage or poor liver function.

An additional test, called a GGT, may be added to the liver panel. This test can indicate that there is damage to the liver or surrounding ducts but does not specify what type of damage is present.

A typical liver function study includes:

  • Aspartate phosphatase (AST), also known as SGOT
  • Alanine aminotransferase (ALT), also known as SGPT
  • Alkaline phosphatase (ALP)
  • Total bilirubin
  • Direct bilirubin
  • Indirect bilirubin
  • Albumin

Liver Function Tests: Uses, Side Effects, Procedures

Arterial Blood Gas

An arterial blood gas, commonly called an ABG, looks at how the respiratory system is functioning and how much oxygen is in the blood. This test requires blood from an artery, which is fully oxygenated by the lungsand is typically drawn from the radial artery in the wrist.

Abnormal results may indicate that the blood is low in oxygen, that the patient is breathing too much or too little (on a ventilator during the surgical procedure), or that they need additional oxygen.

The ABG is typically performed at least once a day when the patient is on a ventilator for an extended period of time. The results are used to determine if any changes in ventilator settings are necessary.

If the patient is in ICU, a special IV called an arterial line may be placed to make drawing arterial blood easier, particularly when it's being done frequently.

A typical ABG includes:

  • pH: The acid/base balance of arterial blood
  • PC02: How much carbon dioxide is in the blood
  • PO2: How much oxygen is being concentrated in the blood
  • HCO3: Bicarbonate levels may indicate kidney function issues
  • O2: How much oxygen is available for the tissues of the body to use

ABG interpretation is very challenging and is typically done by physicians or providers.

Arterial Blood Gas Testing

(Video) Introduction to lab values and normal ranges | Health & Medicine | Khan Academy

ABO Typing

ABO typing is the medical term for determining the patient's blood type. This is done prior to surgery, so blood can be given in the operating room if necessary. Most surgeries do not require a blood transfusion, but some procedures, such as on-pump heart bypass surgery, routinely require the administration of blood.

You may be asked to sign a consent form for the administration of blood prior to your surgery, even if a transfusion is not a routine part of the procedure, in case the need arises.

Blood Culture and Sensitivity

A blood culture is a process where a small sample of your blood is drawn into a bottle of sterile culture medium that "feeds" bacteria.The sample is kept warm and after a few days, it is checked to see if bacteria is growing. If bacteria are growing, it is likely that the same bacteria is growing in your blood.

If bacteria grow, it is then exposed to different antibiotics to see which antibiotic is the most effective for treating your infection. This is a scientific way to choose the best antibiotic for your infection without giving you multiple antibiotics and hoping one works well.

A Word From Verywell

While it is helpful to have a general understanding of lab results and what they mean, the healthcare provider is ultimately responsible for interpreting the results and determining how to respond to them.

Interpreting lab results is a skill that is honed over the years, so don't feel a need to understand every nuance of your lab results.It is far more important that you listen closely when the provider is explaining their plan and how they would like to proceed with your care.

14 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  1. Devereaux PJ, Biccard BM, Sigamani A, et al. Association of postoperative high-sensitivity troponin levels with myocardial injury and 30-day mortality among patients undergoing noncardiac surgery. JAMA. 2017;317(16):1642-1651.doi:10.1001/jama.2017.4360

  2. Rachakonda KS, Parr M, Aneman A, Bhonagiri S, Micallef S. Rational clinical pathology assessment in the intensive care unit. Anaesth Intensive Care. 2017;45(4):503-510.doi:10.1177/0310057X1704500415

    (Video) Complete Blood Count (CBC) Test Results Interpretation w/ Differential Nursing NCLEX

  3. MedlinePlus. Basic metabolic panel.

  4. Mount Sinai. Basic metabolic panel.

  5. Cleveland Clinic. Complete blood count.

  6. MedilinePlus. Complete blood count (CBC).

  7. Thiruvenkatarajan V, Pruett A, Adhikary SD. Coagulation testing in the perioperative period. Indian J Anaesth. 2014;58(5):565-72. doi:10.4103/0019-5049.144657

  8. MedlinePlus. Liver function tests.

  9. Gamma-glutamyl transferase (GGT) blood test. US National Library of Medicine.

  10. University of Rochester Medical Center. Arterial blood gas (ABG).

  11. Mohammed HN, Abdelatief DA. Easy blood gas analysis: Implications for nursing. Egyptian Journal of Chest Diseases and Tuberculosis. 2016;65(1):369-276. doi:10.1016/j.ejcdt.2015.11.009

  12. Yap CYF, Aw TC. Arterial blood gases. Proceedings of Singapore Healthcare. 2011;20(3). doi:10.1177/201010581102000313

  13. Pei Z, Szallasi A. Prevention of surgical delays by pre-admission type and screen in patients with scheduled surgical procedures: improved efficiency. Blood Transfus. 2015;13(2):310-2. doi:10.2450/2014.0172-14

  14. University of Rochester Medical Center. Blood culture.

Additional Reading

By Jennifer Whitlock, RN, MSN, FN
Jennifer Whitlock, RN, MSN, FNP-C, is a board-certified family nurse practitioner. She has experience in primary care and hospital medicine.

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(Video) Full Blood Count – what it tells your doctor about your health

FAQs

How do you analyze blood test results? ›

Lab results are often shown as a set of numbers known as a reference range. A reference range may also be called "normal values." You may see something like this on your results: "normal: 77-99mg/dL" (milligrams per deciliter). Reference ranges are based on the normal test results of a large group of healthy people.

How do I read my blood test results UK? ›

Reading your results
  1. Result: May be numerical or text (e.g. Positive or negative)
  2. Reference range: tells you within what range you would expect a normal result to lie.
  3. Flag: Tells you whether a result is outside of the expected range. ...
  4. Units: Tells you what the test is measured in.
31 May 2018

What shows up in a common blood test? ›

Complete blood count (CBC) The complete blood count (CBC) is one of the most common blood tests. It is often done as part of a routine checkup. This test measures many different parts of your blood, including red blood cells, white blood cells, and platelets.

What are the most important blood test results? ›

Here are the 10 most important blood tests for determining your health status.
  1. Complete Metabolic and Lipid Panel. This is the test you might receive at an annual physical. ...
  2. Vitamin D-25 Hydroxy. ...
  3. Hemoglobin A1C. ...
  4. DHEA. ...
  5. Homocysteine. ...
  6. C-reactive protein. ...
  7. Thyroid-stimulating hormone. ...
  8. Testosterone (free testosterone)

What are the 5 main blood tests? ›

Common ones include:
  • Complete blood count (CBC). This test measures different parts of your blood, including red and white blood cells, platelets, and hemoglobin. ...
  • Basic metabolic panel. ...
  • Blood enzyme tests. ...
  • Blood tests to check for heart disease. ...
  • Blood clotting tests, also known as a coagulation panel.
9 Mar 2021

What are the three main blood tests? ›

A blood test is typically composed of three main tests: a complete blood count, a metabolic panel and a lipid panel.

What are the inflammatory markers in blood? ›

The three most commonly used inflammatory markers are called C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and plasma viscosity (PV).

What do the Colours mean on blood test? ›

The tests each bottle is used for are the same: the purple one is for cell count, the yellow one is for electrolytes, albumin and LDH, the grey one is for glucose, and blood culture bottles can be used for fluid cultures.

What should I look for in a blood test report? ›

Red blood cells (RBCs) White blood cells (WBCs) Platelets. Hemoglobin (protein in RBCs)
...
The abnormal levels of these lab tests can indicate:
  • Lack of enough blood cells.
  • Nutritional deficiencies, such as vitamin B6 or B12.
  • Tissue inflammation.
  • Iron deficiency.
  • Signs of an infection.
  • Heart conditions.
16 Mar 2021

What should you not do before a blood test? ›

Avoiding specific foods and drinks such as cooked meats, herbal tea, or alcohol. Making sure not to overeat the day before a test. Not smoking. Avoiding specific behaviors such as strenuous exercise or sexual activity.

What does MCV mean in a blood test? ›

MCV stands for mean corpuscular volume. An MCV blood test measures the average size of your red blood cells. Red blood cells carry oxygen from your lungs to every cell in your body.

What are the 5 classic signs of inflammation? ›

Based on visual observation, the ancients characterised inflammation by five cardinal signs, namely redness (rubor), swelling (tumour), heat (calor; only applicable to the body' extremities), pain (dolor) and loss of function (functio laesa).

What blood tests show chronic inflammation? ›

A CRP test may be used to help find or monitor inflammation in acute or chronic conditions, including: Infections from bacteria or viruses. Inflammatory bowel disease, disorders of the intestines that include Crohn's disease and ulcerative colitis.

What cancers have high CRP? ›

Additionally, elevated CRP levels are associated with poor survival in many malignant tumors, such as soft tissue sarcoma, prostate cancer, breast cancer, renal cell carcinoma, colorectal cancer, non-small-cell lung cancer, malignant lymphoma, and pancreatic cancer (10, 13-20).

What is a flag on blood test? ›

Flags: for paper results

On lab printouts, labs that are abnormal are indicated with a mark. There is often an empty column with marks identifying which rows contain abnormal bloodwork results. The mark may be an asterisk, or an "H" for high or "L" for low or "A" for abnormal.

What is a yellow blood test for? ›

The gold (or 'yellow') top is used for a wide range of biochemistry tests. The gold top, also known as the 'yellow' top, is one of the most commonly used blood bottles. It is used for a whole variety of biochemistry tests ranging from urea & electrolytes to lipid profiles.

Why are colonoscopies not recommended after age 75? ›

There are risks involved with colonoscopy, such as bleeding and perforation of the colon, and also risks involved with the preparation, especially in older people,” Dr. Umar said.

What age do you stop doing colonoscopies? ›

There's no upper age limit for colon cancer screening. But most medical organizations in the United States agree that the benefits of screening decline after age 75 for most people and there's little evidence to support continuing screening after age 85. Discuss colon cancer screening with your health care provider.

What are the three most common functional tests for older adults? ›

Among the most commonly used instruments, the usual gait speed test, the Short Physical Performance Battery, the handgrip strength, the Timed Up-and-Go test, the 6-minute walk test, and the 400-meter walk test are widely adopted by clinicians and researchers.

How much water should you drink before a blood test? ›

Ideally, start drinking more fluids the day before your blood draw, and continue to drink water before you have your blood drawn. Excessive amounts aren't necessary; most sources ecommend that an adult drink 64 ounces of water per day for good health, which is more than adequate for having your blood drawn.

What's the best thing to drink before blood work? ›

It's actually good to drink water before a blood test. It helps keep more fluid in your veins, which can make it easier to draw blood.

What is best to drink before blood test? ›

Fasting means you don't eat or drink anything but water usually for 8 to 12 hours beforehand. If your appointment is at 8 a.m. and you're told to fast for 8 hours, only water is OK after midnight. If it's a 12-hour fast, avoid food and drink after 8 p.m. the night before.

What tests should be done at age 60? ›

Medical Tests for Your 60s and Up
  • Blood pressure. ...
  • Stepping on the scales. ...
  • Colorectal cancer screening. ...
  • Prostate cancer screening. ...
  • For women, a breast exam and mammogram. ...
  • For women, a pelvic exam, Pap smear and HPV test. ...
  • Protecting your eyes. ...
  • Hearing test.
12 Sept 2020

What tests should a woman have at 65? ›

All women age 65 or older should have a bone density test (DEXA scan).
...
  • Women may do a monthly breast self-exam. ...
  • Your provider may do a clinical breast exam during your preventive exam. ...
  • Women up to age 75 should have a mammogram every 1 to 2 years, depending on their risk factors, to check for breast cancer.

What tests should a 55 year old woman have? ›

What are the recommended medical tests by age 50?
  • Blood pressure check. ...
  • Bloodwork. ...
  • Colorectal cancer screening. ...
  • Immunizations. ...
  • Skin and mole check. ...
  • Joint care assessment. ...
  • Vision exam.
17 Aug 2020

What do doctors look for in blood test results? ›

Blood tests can be used for many different things, including to check cholesterol and blood glucose levels. These help monitor your risk of heart and circulatory diseases and diabetes, or how your condition is being managed. Tests for different chemicals and proteins can indicate how your liver or kidneys are working.

What should I look for in a blood test report? ›

Red blood cells (RBCs) White blood cells (WBCs) Platelets. Hemoglobin (protein in RBCs)
...
The abnormal levels of these lab tests can indicate:
  • Lack of enough blood cells.
  • Nutritional deficiencies, such as vitamin B6 or B12.
  • Tissue inflammation.
  • Iron deficiency.
  • Signs of an infection.
  • Heart conditions.
16 Mar 2021

What is a normal blood analysis? ›

A routine complete blood count (CBC) checks for levels of 10 different components of every major cell in your blood: white blood cells, red blood cells, and platelets. Important components this test measures include red blood cell count, hemoglobin, and hematocrit.

What are normal ranges for blood test results? ›

Normal Laboratory Values
Laboratory TestNormal Range in US UnitsNormal Range in SI Units
High160-189 mg/dL4.14 – 4.89 mmol/L
Very High>190 mg/dL>4.91 mmol/L
Cholesterol, HDL>60 mg/dL>1.55 mmol/L
Moderate40-60 mg/dL1.03-1.55 mmol/L
36 more rows

Do doctors check for everything in a blood test? ›

They test the blood for white blood cells, red blood cells, hemoglobin, hematocrit, and platelets. CBC tests can detect if you have anemia, nutritional deficiencies, an infection, cancer, and bone marrow problems. If any of these results come back as abnormal, your doctor may order more specific testing.

What should you not do before a blood test? ›

Avoiding specific foods and drinks such as cooked meats, herbal tea, or alcohol. Making sure not to overeat the day before a test. Not smoking. Avoiding specific behaviors such as strenuous exercise or sexual activity.

Would a full blood count show anything serious? ›

Full blood count (FBC)

This can help give an indication of your general health, as well as provide important clues about certain health problems you may have. For example, an FBC may detect signs of: iron deficiency anaemia or vitamin B12 deficiency anaemia. infection or inflammation.

What is Flag A on test results? ›

Flags: for paper results

The mark may be an asterisk, or an "H" for high or "L" for low or "A" for abnormal. In this printout, normal results are indicated with an "N". Results outside the range of normal have an "A".

What indicates infection in a blood test? ›

If your white blood cell count is higher than normal, you may have an infection or inflammation. Or, it could indicate that you have an immune system disorder or a bone marrow disease. A high white blood cell count can also be a reaction to medication.

What is Flag H in blood test? ›

If your blood counts fall outside of the normal range, which is shown in the “Reference interval” column, their values will be reported in the “Flag” column with an 'L' for low and an 'H' for high.

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