What color tube is used for ammonia blood test

test tube for ammonia blood test

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Blood tests are crucial in healthcare, offering insights into the body’s intricate functions. They are the key to identifying illnesses, tracking health, and informing medical treatment. The test measuring ammonia in your blood is essential for assessing liver health. 

This organ is supposed to convert the potentially harmful ammonia into a safer substance known as urea. Elevated ammonia could signal liver dysfunction or other metabolic disturbances. Thus, this particular test is precious for physicians to uncover and address potential health concerns that may not be immediately apparent.

ammonia blood test

Tube Is Used for Ammonia Blood Test

The appropriate tube color for an ammonia blood test is purple. Understanding the intricacies of blood collection tubes and their intended uses is essential to ensure accuracy in diagnostic testing. The blood test for ammonia levels helps determine the ammonia concentration in someone’s bloodstream. 

When ammonia levels rise, it can be harmful and usually points to the liver failing to turn ammonia into urea properly, which is vital for getting rid of waste substances. For individuals exhibiting symptoms indicative of liver impairment, possible hepatic encephalopathy, or various metabolic disorders, this diagnostic evaluation becomes especially critical.

For the ammonia blood test, we utilize a heparinized green-topped tube. This collection tube is coated with lithium heparin, an anticoagulant that prevents blood from clotting. During the blood draw, heparin is essential as it inhibits key clot-forming elements, particularly thrombin and thromboplastin, ensuring a smooth collection. 

These factors are critical to the blood’s natural clotting mechanism, and their inhibition by heparin ensures the sample remains fluid. For ammonia level assessment, this characteristic of heparin is particularly advantageous because it allows the substance to preserve the sample without altering the ammonia content. 

Therefore, drawing blood into a heparinized green-topped tube is critical for the ammonia test to secure an accurate representation of the ammonia levels, enabling precise diagnostic outcomes.

what color tube is used for ammonia blood test

The green-topped tube is integral to the testing process for several reasons:

Anticoagulation: Immediate plasma separation is required in ammonia testing as ammonia levels can increase in the sample due to red blood cell metabolism if the blood clots. The heparin ensures the blood remains liquid, allowing for prompt plasma separation.

Preventing Preanalytical Variability: The presence of heparin minimizes the chances of pre-analytical variables that could alter the ammonia levels. Such variables include changes in pH or the breakdown of blood cells.

Sample Integrity: The integrity of the blood sample is maintained, as the absence of clotting allows for consistent plasma quality, which is necessary for reliable results.

Using the correct type of tube for the ammonia test is paramount. If an incorrect tube is used—such as one containing a different anticoagulant or a clot activator—the ammonia test results could be compromised. 

For instance, tubes with additives that are not inert could react chemically with the ammonia or influence its production or degradation in the sample, leading to falsely elevated or decreased levels. Such inaccuracies can result in misdiagnosis or inappropriate treatment. 

In a clinical setting, this could mean the difference between timely intervention and a missed opportunity to address a potentially life-threatening condition. Faulty test results have the potential to cause unwarranted stress for patients, lead to subsequent testing, and may result in excessive treatments.

Importance of Correct Tube Selection

Significance of Correct Tube Selection

Preservation of Sample Integrity: Certain tests require plasma, others serum, and some others whole blood. For instance, coagulation tests require plasma from blood collected in a tube containing an anticoagulant like sodium citrate, which preserves clotting factors.

Prevention of Test Interference: Additives in the wrong tube can interfere with the test result. An EDTA tube, for example, chelates calcium, and using it for a calcium test would yield inaccurate results.

Stabilization of Blood Component: Tubes with anticoagulants are essential for complete blood counts (CBC), as they prevent clotting and preserve cell morphology.

Downsides of Incorrect Tube Selection:

  • Hemolysis: Using a tube with an inappropriate additive or a vacuum that is too strong can lead to cell lysis, releasing intracellular contents and distorting test results.
  • Clotting: If a coagulation profile is drawn in a tube without anticoagulant, clotting may occur, rendering the sample useless and delaying diagnosis.
  • Contamination: Some tubes contain substances that can contaminate the sample if used for the wrong test, such as EDTA contaminating chemistry assays.

Examples of Negative Impacts on Patient Outcomes:

A patient’s potassium levels might appear falsely elevated (pseudohyperkalemia) if collected in an EDTA tube, leading to unnecessary treatment for hyperkalemia.

Coagulation tests performed on a clotted sample might suggest a bleeding disorder, prompting unwarranted further testing and anxiety.

Tips and Guidance for Medical Professionals:

  • Tube Selection: Familiarize yourself with the color-coded system of tubes and their corresponding tests.
  • Order of Draw: Follow the recommended order of draw to prevent cross-contamination of additives between tubes.
  • Training and Protocols: Regularly train staff on proper phlebotomy techniques and keep updated protocols accessible.
  • Quality Control: Implement a quality control program to check for sampling and handling errors routinely.
  • Patient Communication: Communicate with patients about the procedures to minimize movement and anxiety can affect the sample quality.
  • Check Expiry Dates: Ensure that tubes are within their shelf life to maintain the efficacy of additives.

Understanding Blood Collection Tubes

Several blood collection tubes are used in clinical settings, each designed for specific tests. These tubes have different sizes, colors, and additives that either promote or inhibit blood clotting, stabilize blood components, or preserve particular analytes. The color-coded tops of these tubes allow quick identification and reduce the risk of pre-analytical errors.

Detailed Overview of Tube Types

Serum Tubes

  • Sizes: Generally range from 2 mL to 10 mL
  • Tops: Red, Gold, or Orange (Gold/Orange tops usually indicate a clot activator and gel for serum separation)
  • Uses: Serum testing, including chemistry tests, serology, and immunology tests
  • Significance: These tubes allow blood to clot, and the serum is separated by centrifugation. Clot activators speed up the clotting process, and the gel creates a barrier between serum and cells after centrifugation.

Plasma Tubes

  • Sizes: Vary depending on the test requirements
  • Tops: Light Blue, Green, purple, Gray, and other variations
  • Uses: Coagulation tests (Light Blue), chemistry tests (Green – heparin additive), hematology (Lavender – EDTA), and glucose tolerance tests (Gray – sodium fluoride)
  • Significance: These tubes contain anticoagulants that prevent clotting and preserve the blood in its liquid form. Each anticoagulant serves a different purpose, affecting which tests the plasma will suit.

Whole Blood Tubes

  • Sizes: Similar to plasma tubes
  • Tops: Usually purple or Pink
  • Uses: Complete blood counts (CBC), blood typing, and specific chemistry tests
  • Significance: These tubes often contain EDTA, which preserves the whole blood without altering the blood cell morphology.

Identifying Contents by Tube Top Color

  • Red Top: No additive or clot activator is used for serum determinations in chemistry.
  • Gold/Orange Top: Serum separator tube (SST) with clot activator and gel for serum separation.
  • Light Blue Top: Contains sodium citrate, an anticoagulant used for coagulation assays.
  • Green Top: Heparin as an anticoagulant, used for plasma determinations in chemistry.
  • Lavender Top: EDTA as an anticoagulant, used for most hematology determinations.
  • Gray Top: Sodium fluoride, a glycolysis inhibitor and anticoagulant, is used for glucose and lactate testing.

Examples of Tests by Tube Color

  • Red Top Tube: Hormone levels, infectious disease tests, and metabolic panels.
  • Gold Top Tube: Lipid panels, liver panels, and infectious disease tests.
  • Light Blue Top Tube: Prothrombin Time (PT), Activated Partial Thromboplastin Time (aPTT).
  • Green Top Tube: Renal function tests, ammonia levels, and STAT electrolytes.
  • Lavender Top Tube: CBC, Erythrocyte Sedimentation Rate (ESR), Sickle Cell Screening.
  • Gray Top Tube: Fasting glucose, glucose tolerance tests, and lactate levels.
EDTA tube

Key Components of the Green-Topped Tube

What’s Heparin Anyway?

Heparin is a type of medicine, but it doesn’t cure anything inside these tubes. Instead, it stops blood from clotting, which is helpful when doctors need to test your blood. Imagine putting fresh juice in a bottle – you wouldn’t want it turning into jelly before you could drink it, right? That’s what heparin prevents with blood in the green-topped tubes.

How Heparin Works Its Magic

When I take your blood, it wants to start clotting immediately – that’s what blood does outside your body. But I need the blood to stay liquid so we can run tests to keep you healthy. Heparin jumps into action by sticking to this thing in your blood called antithrombin III (I know, it sounds like a space movie character). Together, they create a tag team that stops clotting in its tracks.

Why I Like Using Heparin Tubes

These green-topped tubes are my go-to because they’re fast. When blood hits the heparin, it’s protected from becoming a clot. Plus, heparin doesn’t mess with any of the machines we use or change how the blood components look so that I can give you accurate test results.

A Couple of Things to Watch Out For

Heparin could be better. In rare cases, it can cause a reaction where your blood platelets drop, but that’s more of an issue if you’re getting heparin as medicine, not just in a tube. There’s always a tiny chance of bleeding more than usual, but again, that’s mainly when it’s used as a treatment.

Keeping Up with Heparin Advances

The people who make heparin are always trying to make it even better. They’ve devised safer and more predictable versions, which is excellent news for everyone. Conversations are underway about creating alternatives that do not rely on animal sources, potentially heralding a significant shift in consumer options.

Ammonia Testing Procedure

Step 1: Preparing for the Test

There’s a bit you need to do before the test. You might have to skip eating for a few hours – your doctor will tell you how long. Refraining from eating before the test is crucial for obtaining precise and unambiguous outcomes.

Step 2: Drawing the Blood

On the day of the test, I sat in a chair, and a lab tech wrapped this band around my arm to make my veins pop. It felt tight, but it wasn’t too bad. They found a good vein, cleaned the spot with antiseptic, and then – whoosh – in went the needle. It was a quick pinch; before I knew it, my blood filled up this special tube.

Step 3: Stopping the Clotting

Remember those green-topped tubes I mentioned earlier? One of them was used here, too. These tubes have a little heparin, which prevents blood from clotting so the lab can test it properly.

Step 4: Keeping It Cool

After they took enough blood, the lab tech pressed some gauze over the spot to stop bleeding. Then, they labeled my blood sample and immediately put it on ice. Ammonia levels can change quickly, so keeping the blood chilled is important to get an accurate reading.

Step 5: The Analysis

My chilled sample was rushed to the lab. Scientists used special machines to measure how much ammonia was in my blood there. Elevated ammonia levels in the body may indicate underlying liver or kidney function issues, as these organs are primarily responsible for processing and eliminating this byproduct.

Factors Affecting Blood Ammonia Levels

Several conditions can lead to altered blood ammonia levels. High ammonia levels in the blood can arise from various medical issues, including liver impairments linked to cirrhosis or hepatitis. Additionally, high alcohol intake can disrupt the liver’s ability to transform ammonia into urea efficiently. 

Furthermore, inherited anomalies in urea cycle enzyme function, critical heart failure, Reye’s syndrome, and various metabolic disorders can also contribute to higher ammonia levels. Timely testing after sample collection is crucial because ammonia levels can rise due to prolonged exposure to room temperature and cellular metabolism. 

Within 20 minutes to an hour of drawing blood, blood samples should be transported on ice and analyzed as soon as possible to preserve the integrity of the test results.

purple color test tube

Handling and Transportation of Blood Samples

Sample Identification

  • Labeling: Every vial must be labeled immediately after collection with the patient’s full name, date of birth, date and time of sample collection, and type of test to be performed.
  • Verification: Double-check the information on the label with the patient’s identification band or documents to ensure accuracy.


  • Technique: Utilize aseptic techniques to prevent contamination.
  • Order of Draw: Follow the correct order of draw when collecting multiple samples to prevent cross-contamination of additives between tubes.
  • Volume: Ensure the correct volume is drawn; insufficient or excessive volume can compromise test results.


  • Immediate Processing: Some blood tests require the sample to be processed immediately, while others can be temporarily stored.
  • Temperature Control: Samples that must be stored should be kept at appropriate temperatures depending on the analyte stability.


  • Secure Packaging: Use leak-proof transport bags and fast tubes in racks or padded containers.
  • Upright Position: Keep blood tubes upright whenever possible to prevent hemolysis and spillage.

Temperature and Timing Considerations for Safe Transportation

Given the variety of tests and the potential for blood samples to deteriorate or give inaccurate results if mishandled, adherence to temperature and timing standards is crucial. The following are the general guidelines; however, they always refer to local regulations and specific test requirements.

Optimum Temperature Ranges for Different Types of Samples

  • Room Temperature (15-25°C): Most routine chemistry and hematology samples.
  • Refrigerated (2-8°C): Hormone assays, drug levels, and specific serology tests.
  • Frozen (-20 °C or colder): Genetic tests, viral loads, and other specialized assays requiring preservation of RNA/DNA.

Safety Precautions to Avoid Contamination

  • Separation: Separate samples that may emit vapors or have high infection risk.
  • Sealed Containers: Use screw-cap tubes and ensure they are tightly sealed.
  • Spill Kits: Always have spill kits and biohazard containers ready in case of accidental breakage or leakage.

Critical Timing Requirements for Laboratory Analysis

  • Stat Samples: Should arrive at the lab within 1 hour of collection for immediate analysis.
  • Routine Samples: Typically processed within 24 hours; verify stability for each test.
  • Frozen Samples: Must be transported to the lab immediately to be frozen upon arrival.

Last words

Using the appropriate tube, specifically a green-top heparinized tube, is a critical step in obtaining accurate ammonia test results. Precise results are essential for correctly diagnosing and managing medical conditions that affect liver and kidney function and metabolic disorders. Incorrect collection methods may lead to faulty data, adversely affecting patient outcomes.

Medical practitioners possess the expertise in current standards to guarantee accurate administration of diagnostic evaluations. Following their guidance ensures that the most cannot be overstated that professional medical advice should be sought for any concerns related to health or testing methods. Reliable results are obtained, which is the cornerstone of effective treatment plans.

Consult a medical expert to determine the most suitable plan for your health requirements. This ensures that all medical evaluations, such as ammonia blood testing, are performed with precision and care.

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