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Medical Tests & Diagnostics Explained
Been told you need a test? These plain-language guides explain medical tests, screenings and diagnostic procedures: why a test is ordered, how to prepare, what happens during it, how to read the results, and what usually comes next. Every guide is medically reviewed by Dr. Baraa Alnahhal, MD, and based on published medical sources. Use them to understand your test and prepare questions for your own doctor; they don't replace personal medical advice.
Browse medical test guides
Gastric Emptying Study in Children (Solid-Meal GES): What to Expect
A solid-meal gastric emptying study (GES) for children is a nuclear medicine test that measures how long food takes to leave the stomach. It's most often used to diagnose gastroparesis and dumping syndrome. The test is painless, needs no sedation and usually takes four to five hours. Your child can't eat after midnight the night before.
Dr. Baraa Alnahhal
6 days ago
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Electronic Fetal Monitoring (EFM): Types, Risks and Results
Electronic fetal monitoring (EFM) is a test that continuously records your contractions and your baby's heart rate during labor, helping providers spot and respond to problems quickly. External EFM uses two sensors held on the belly; internal EFM uses a small wire attached to the baby's scalp. Low-risk, unmedicated labors may not need continuous monitoring.
Dr. Baraa Alnahhal
6 days ago
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Cardiac Blood Tests: Heart Disease Risk Tests and Ideal Levels
Cardiac blood tests are blood tests that help estimate your risk of heart and blood vessel disease, such as a heart attack or stroke. They include a cholesterol panel plus more specialized tests, such as lipoprotein (a), C-reactive protein and hemoglobin A1c. You may need to fast for 9 to 12 hours.
Dr. Baraa Alnahhal
6 days ago
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Enzyme Markers: Blood Tests for Heart, Liver and Muscle Damage
Enzyme markers, also called biomarkers, are blood tests that measure enzymes and other proteins that leak into the blood when tissues are damaged or stressed. They help diagnose a heart attack, check for liver disease and find muscle damage. Common examples include troponin, liver enzymes like ALT and AST, and creatine kinase (CK).
Dr. Baraa Alnahhal
6 days ago
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AST Blood Test (Aspartate Transferase): Normal Range and Results
An aspartate transferase (AST) test is a blood test that measures AST, an enzyme found mostly in the liver. It's most often used to check liver health, usually alongside the ALT test. One common normal range is 8 to 33 U/L, though it varies by lab. High AST can point to hepatitis, cirrhosis or alcohol-related liver injury.
Dr. Baraa Alnahhal
6 days ago
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Cisternogram Scan: Tracking Spinal Fluid Flow and Leaks
A cisternogram scan is a nuclear medicine imaging test that shows how cerebrospinal fluid (CSF) flows around the brain and spinal cord. A radioactive tracer is injected into the spinal fluid during a lumbar puncture, and images are taken over 1 to 3 days. It's used to find a CSF leak or a buildup of CSF, such as hydrocephalus.
Dr. Baraa Alnahhal
6 days ago
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Acetaminophen Level Test: Checking for Tylenol Overdose
An acetaminophen level test is a blood test that measures how much acetaminophen (Tylenol) is in the blood. It's used to diagnose a suspected acetaminophen overdose and guide treatment. Too much acetaminophen can cause serious liver damage, sometimes before symptoms appear. The test is usually done about 4 hours after the dose, and treatment works best when started early.
Dr. Baraa Alnahhal
6 days ago
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Contrast Enema for Children: What to Expect for Your Child
A contrast enema for children, also called a pediatric barium enema, is an X-ray test that uses contrast and fluoroscopy (X-ray video) to look at a child's colon. It's most often done to find out why a child has trouble pooping. Your child stays awake and needs no sedation. The test takes 30 to 45 minutes.
Dr. Baraa Alnahhal
6 days ago
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Gastrointestinal (GI) Tests: Types, Preparation and What to Expect
Gastrointestinal (GI) tests and exams are procedures used to find problems in the esophagus, stomach, small intestine, large intestine and rectum. The three main groups are imaging tests, endoscopy, and lab and functional tests of blood, breath, stool or tissue. Preparation ranges from none to fasting and bowel prep, depending on the test.
Dr. Baraa Alnahhal
6 days ago
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MUGA Scan: Measuring How Well Your Heart Pumps
A MUGA scan (multigated acquisition scan) is a nuclear heart imaging test that shows how well the heart pumps by measuring the ejection fraction (EF), the percentage of blood pumped with each beat. It's used to check for heart failure and monitor the heart during cancer treatments that can harm it. A typical EF is 50% to 75%.
Dr. Baraa Alnahhal
6 days ago
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T3 (Triiodothyronine) Test: Normal Levels and What Results Mean
A triiodothyronine (T3) test is a blood test that measures T3, one of the two main hormones the thyroid makes. It's mainly used to help diagnose hyperthyroidism (an overactive thyroid) and to monitor people taking thyroid hormone medicine. It's usually ordered with a T4 test and a TSH test. T3 isn't typically used to diagnose an underactive thyroid.
Dr. Baraa Alnahhal
6 days ago
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DLCO Lung Diffusion Test: Purpose, Normal Range and Results
A lung diffusion test (DLCO) is a pulmonary function test that measures how well oxygen moves from the lungs into the blood. You breathe in a safe, tiny amount of carbon monoxide, hold your breath for 10 seconds, then breathe out into a machine. A result of 75% to 140% of the predicted value is normal.
Dr. Baraa Alnahhal
6 days ago
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Cardiac PYP Scan: Testing for ATTR Cardiac Amyloidosis
A cardiac PYP scan, or pyrophosphate scan, is a noninvasive nuclear imaging test that shows whether transthyretin amyloidosis (ATTR) is causing cardiac amyloidosis, a condition where abnormal proteins build up in the heart muscle. It helps tell ATTR apart from AL amyloidosis and often avoids the need for a heart biopsy. Expect to spend 3 to 4 hours.
Dr. Baraa Alnahhal
6 days ago
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Partial Thromboplastin Time (PTT) Test: Normal Range and Results
A partial thromboplastin time (PTT) test is a blood test that measures how long the blood takes to form a clot. A normal PTT is about 25 to 35 seconds, though ranges vary by lab. It's used to investigate unusual bleeding or bruising, check bleeding risk before a procedure and monitor heparin, a blood thinner.
Dr. Baraa Alnahhal
6 days ago
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Carotid Intima-Media Thickness (CIMT) Test: Checking Artery Walls
A carotid intima-media thickness (CIMT) test is a painless ultrasound that measures the thickness of the inner two layers of the carotid artery walls in the neck. Thicker walls can be an early sign of atherosclerosis and a higher risk of heart attack and stroke. It needs no preparation, uses no radiation and takes 30 to 45 minutes.
Dr. Baraa Alnahhal
6 days ago
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Blood Volume Testing: How It Works and What Results Mean
Blood volume testing is a nuclear medicine test that measures how much blood is in the body and compares it with what's normal for your height, weight and sex. A small amount of radioactive tracer is injected into a vein, and several blood samples are drawn. It's used mostly in intensive care. The test takes under 90 minutes.
Dr. Baraa Alnahhal
6 days ago
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Cardiac Telemetry Monitoring: Real-Time Heart Rhythm Monitoring
Cardiac telemetry monitoring is the continuous, real-time recording of the heart rhythm, usually in a hospital. Electrode patches on the chest send the heart's electrical signals to a central monitor watched by trained staff, so they can respond quickly to dangerous rhythm changes. It's used for chest pain, palpitations, a heart attack, stroke, fainting or after surgery.
Dr. Baraa Alnahhal
6 days ago
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Corneal Pachymetry: Measuring Corneal Thickness for Glaucoma and LASIK
A corneal pachymetry test is a quick, painless test that measures the thickness of the cornea, the clear dome at the front of the eye. It's important for glaucoma care, because corneal thickness affects eye pressure readings and a thinner cornea is linked to higher glaucoma risk. It's also required before LASIK. Results are available right away.
Dr. Baraa Alnahhal
6 days ago
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Liver-Spleen Scan: Nuclear Imaging of Liver and Spleen Function
A liver-spleen scan is a nuclear medicine imaging test that shows how well the liver and spleen are working. A radioactive tracer is injected into a vein, and a gamma camera creates pictures. It's used to monitor chronic liver disease such as cirrhosis, find liver or spleen lesions and assess injury after trauma. The test takes an hour.
Dr. Baraa Alnahhal
6 days ago
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Fractional Flow Reserve (FFR): Deciding Whether You Need a Stent
Fractional flow reserve (FFR) is a test done during a coronary angiogram that measures how much a narrowed heart artery limits blood flow. A normal FFR is 0.94 to 1. An FFR of 0.80 or higher usually means the narrowing can be treated with medicine, while lower values usually mean a stent will help.
Dr. Baraa Alnahhal
6 days ago
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Bacteria Culture Test: Types, How It Works and Results
A bacteria culture test is a lab test that checks a sample of blood, urine, stool, mucus, skin, a wound or spinal fluid to see whether bacteria are growing and causing an infection. A follow-up antibiotic susceptibility test often shows which antibiotics will work best. Most cultures need no preparation, and results take about 1 to 5 days.
Dr. Baraa Alnahhal
6 days ago
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Heart Biopsy (Endomyocardial Biopsy): Procedure, Risks and Results
A heart biopsy, also called an endomyocardial or cardiac biopsy, removes tiny pieces of tissue from the inner lining of the heart muscle for examination under a microscope. It's used to check for rejection after a heart transplant and to diagnose conditions such as myocarditis and cardiomyopathy. Serious complications occur in fewer than 1% of cases.
Dr. Baraa Alnahhal
6 days ago
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Testicular Ultrasound: Checking Lumps, Pain and Swelling
A testicular ultrasound, also called a scrotal ultrasound, uses sound waves to create pictures of the testicles and nearby tissues. It's the main imaging test for lumps, swelling, pain or injury in the scrotum. It can find testicular cancer, cysts and testicular torsion, which needs emergency surgery. The test is painless and takes under 30 minutes.
Dr. Baraa Alnahhal
6 days ago
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Spurling Test: Checking for a Pinched Nerve in the Neck
The Spurling test is a quick physical exam that helps diagnose cervical radiculopathy, a pinched nerve in the neck. The provider tilts your head toward the side of your symptoms and presses lightly on top. Pain, numbness or tingling that travels into the shoulder or arm means a positive test. A negative test doesn't fully rule it out.
Dr. Baraa Alnahhal
6 days ago
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