Blood Test: What to Expect and What Your Results Mean

A blood test is a common laboratory procedure in which a small sample of your blood is collected and analyzed to evaluate your overall health, screen for medical conditions, or monitor a diagnosis you already have. The sample is checked for blood cells, chemicals, proteins, and other markers that show how well your organs and body systems are functioning.

The Blood Ammonia Test measures the level of ammonia in your bloodstream. Ammonia is a waste product that is normally processed by your liver and excreted from your body. When your liver cannot properly remove ammonia, it can build up in your blood and potentially reach your brain, causing serious health problems.

Your doctor may order this test to help diagnose the cause of symptoms such as fatigue, weakness, or unexplained changes in your body, to screen for conditions before they cause problems, to check how well your organs are working, or to track whether a treatment or medication is helping you as expected.

Your doctor may order this test if you have symptoms such as confusion, drowsiness, trembling hands, or difficulty speaking. It is commonly used to: assess liver function, monitor liver disease progression, evaluate for hepatic encephalopathy (a condition where liver disease affects brain function), and detect certain metabolic or genetic disorders.

Preparation is usually simple. Continue taking your regular medications unless your doctor tells you otherwise, and drink plenty of water so your veins are easier to find. If fasting is required, avoid all food and drinks except water for 8 to 12 hours before the test. Wear a shirt with loose sleeves so the draw site on your arm is easy to reach.

Follow these important preparation steps: Fast (do not eat) for 8-12 hours before the test as instructed by your doctor. Avoid smoking before the test, as smoking can increase ammonia levels. Inform your doctor about all medications you are taking, as some medicines can affect test results. Avoid strenuous exercise before the test, as exercise can temporarily increase ammonia levels. Rest quietly before having your blood drawn.

A trained phlebotomist will wrap an elastic band around your upper arm, clean the site with an antiseptic, and insert a thin needle into a vein, usually in your arm. You may feel a quick pinch or a slight sting. The blood is collected into one or more small tubes, the needle is removed, and a bandage is applied. The whole process usually takes less than ten minutes.

A healthcare professional will draw a small blood sample from a vein in your arm using a needle. The sample will be placed in a special tube and sent to a laboratory for analysis. The test itself takes only a few minutes, and you may experience minor discomfort or bruising at the injection site.

Your report will list your values next to a reference range, which represents the levels typically seen in healthy people. A value slightly outside the range does not always mean something is wrong, because factors such as age, diet, hydration, and medications can affect results. Review your results with your doctor, who will explain what they mean for you and whether any follow-up testing or treatment is needed.

Normal ammonia levels typically range from 15 to 45 micromoles per liter (μmol/L), though reference ranges may vary by laboratory. High ammonia levels (hyperammonemia) may indicate liver disease, liver failure, hepatitis, cirrhosis, or certain metabolic disorders. Your doctor will interpret your results based on your overall health, symptoms, and other test results.