DecodeMyChart — Medical Abbreviation & Lab Value Reference
The most comprehensive plain-English guide to medical abbreviations, lab result interpretation, and healthcare terminology — free for patients, caregivers, students, and anyone trying to understand their medical records.
This site covers 238 medical abbreviations across 20 clinical categories including general medicine, pharmacy, cardiology, labs, emergency medicine, neurology, pulmonology, orthopedics, gastroenterology, oncology, OB/GYN, psychiatry, pediatrics, endocrinology, nephrology, dermatology, rehabilitation, and medical billing. For lab results, the interactive tool lets you enter your value and instantly see whether it falls within the normal reference range, with plain-English explanations of what abnormal results may mean.
General Medical Terms
SOB — Shortness of Breath
Difficulty breathing or feeling breathless. One of the most common symptoms documented in medical charts. Shortness of breath can be caused by conditions ranging from anxiety, asthma, and pneumonia to heart failure, pulmonary embolism, and COPD. When shortness of breath occurs only during physical activity, it is documented as DOE (dyspnea on exertion). When it worsens lying flat, it is called orthopnea and is often a sign of heart failure.
CC — Chief Complaint
The primary reason the patient is seeking medical care, recorded in the patient's own words. The chief complaint is always the starting point of every clinical encounter. Examples include "chest pain for two days," "shortness of breath getting worse," or "swelling in my right leg." The chief complaint guides the history of present illness and the entire diagnostic workup.
HPI — History of Present Illness
A detailed narrative describing the patient's current medical problem, including when it started, what makes it better or worse, associated symptoms, and how it has progressed over time. The HPI is one of the most important parts of a clinical note and is typically recorded in SOAP format (Subjective, Objective, Assessment, Plan).
PMH — Past Medical History
A complete record of the patient's prior medical conditions, diagnoses, hospitalizations, surgeries, and significant medical events. The past medical history helps clinicians understand a patient's baseline health status and identify relevant risk factors. Common abbreviations within PMH include HTN (hypertension), DM (diabetes mellitus), CAD (coronary artery disease), and GERD (gastroesophageal reflux disease).
NPO — Nothing by Mouth
From the Latin nil per os, meaning the patient must not eat, drink, or take anything by mouth. NPO orders are required before surgery, most procedures requiring anesthesia or sedation, and certain diagnostic tests. Patients on NPO orders receive hydration and medications through intravenous (IV) lines. Violation of NPO status can result in aspiration of stomach contents into the lungs during anesthesia, which can be life-threatening.
DNR — Do Not Resuscitate
A legally binding medical order specifying that if the patient's heart stops or they stop breathing, no cardiopulmonary resuscitation (CPR) or resuscitation efforts should be performed. DNR orders are based on the patient's own wishes or those of their legal healthcare proxy, established through advance directives and goals of care conversations. DNR is often documented alongside DNI (do not intubate), which specifies the patient should not be placed on mechanical ventilation.
Dx, Tx, Sx, Rx — Diagnosis, Treatment, Symptoms, Prescription
These four abbreviations are among the most universally used in medicine. Dx is the diagnosis — the identified disease or condition. Tx is the treatment plan. Sx refers to symptoms reported by the patient. Rx is a prescription or treatment order. These shorthand forms appear on discharge summaries, after-visit notes, and clinical documentation throughout the medical record.
WNL — Within Normal Limits
A common charting shorthand indicating that a physical examination finding, test result, or measurement falls within the expected normal range for a patient of that age and sex. When clinicians document "heart and lungs WNL," it means the cardiac and pulmonary exam found nothing outside of normal. WNL is sometimes jokingly expanded to "we never looked" in medical humor, emphasizing the importance of actually documenting specific findings.
Lab Values and Normal Ranges
For each lab value below, DecodeMyChart provides an interactive checker where you can enter your specific result and instantly see whether it is normal, low, or high, along with a plain-English explanation of what the result may mean.
CBC — Complete Blood Count
The most commonly ordered blood test in medicine, measuring five key components: white blood cells (WBC), red blood cells (RBC), hemoglobin (Hgb), hematocrit (Hct), and platelets (Plt). A CBC is ordered to screen for anemia, infection, bleeding disorders, and many other conditions. It is routinely ordered as part of annual wellness exams, pre-operative workups, and evaluations of fatigue, fever, or unexplained weight loss.
WBC — White Blood Cell Count (Normal range: 4.5–11.0 K/uL)
White blood cells are the immune system's primary infection-fighting cells. A high WBC count (leukocytosis, above 11.0) typically signals infection, inflammation, or stress on the body. It can also be caused by certain medications, steroids, or in rare cases, leukemia. A low WBC (leukopenia, below 4.5) may result from viral infections, autoimmune conditions, bone marrow problems, or chemotherapy side effects. The WBC differential breaks down the specific types of white cells, helping identify the nature of the problem.
Hgb — Hemoglobin (Normal range: 11.5–17.5 g/dL)
Hemoglobin is the protein inside red blood cells that binds and carries oxygen from the lungs to all tissues in the body. Low hemoglobin is the defining finding of anemia, causing fatigue, pallor, shortness of breath, and reduced exercise tolerance. The most common causes of low hemoglobin are iron deficiency (especially in menstruating women), vitamin B12 or folate deficiency, chronic kidney disease, and chronic inflammatory conditions. High hemoglobin can indicate dehydration, chronic lung disease, or polycythemia vera.
HbA1c — Hemoglobin A1c (Normal range: 4.0–5.7%)
Hemoglobin A1c is a critically important blood test that reflects the average blood glucose level over the past two to three months by measuring the percentage of hemoglobin that has glucose attached to it. Because it captures long-term blood sugar control rather than a single moment, it is the gold standard for diagnosing and monitoring diabetes. A result of 5.7 to 6.4 percent indicates prediabetes, while 6.5 percent or above on two separate tests confirms a diabetes diagnosis. For most diabetic patients, the treatment goal is below 7 percent. Each one percent reduction in HbA1c significantly reduces the risk of diabetic complications including kidney disease, blindness, and nerve damage.
TSH — Thyroid-Stimulating Hormone (Normal range: 0.4–4.0 mIU/L)
TSH is produced by the pituitary gland and regulates how much thyroid hormone the thyroid gland makes. Paradoxically, a high TSH means the thyroid is underactive (hypothyroidism) — the pituitary is working harder to stimulate a sluggish thyroid. A low TSH means the thyroid is overactive (hyperthyroidism). Hypothyroidism causes fatigue, weight gain, cold intolerance, constipation, and depression, and is treated with levothyroxine. Hyperthyroidism causes weight loss, rapid heartbeat, anxiety, heat intolerance, and tremors, and is treated with medications, radioactive iodine, or surgery.
BMP and CMP — Basic and Comprehensive Metabolic Panels
The basic metabolic panel (BMP) measures eight values: sodium, potassium, chloride, bicarbonate, blood urea nitrogen (BUN), creatinine, glucose, and calcium. These values assess kidney function, electrolyte balance, acid-base status, and blood sugar. The comprehensive metabolic panel (CMP) adds liver function tests including ALT, AST, alkaline phosphatase, bilirubin, albumin, and total protein, providing a more complete picture of organ health. Both panels are routinely ordered for annual physicals, hospital admissions, and monitoring of chronic conditions.
INR — International Normalized Ratio (Normal range: 0.8–1.1)
The INR is a standardized measurement of how long blood takes to clot through the extrinsic coagulation pathway. For patients not on blood thinners, a normal INR is close to 1.0. Patients taking warfarin (Coumadin) for conditions like atrial fibrillation or mechanical heart valves require regular INR monitoring, with a therapeutic target typically between 2.0 and 3.0. An INR above 3.5 significantly increases the risk of dangerous bleeding, while an INR below the therapeutic range increases clot risk. INR levels are affected by diet (especially vitamin K-rich foods), other medications, and illness.
LDL and HDL — Cholesterol Values
LDL (low-density lipoprotein) is commonly called bad cholesterol because elevated LDL promotes the buildup of plaque in artery walls (atherosclerosis), increasing the risk of heart attack and stroke. The optimal LDL is below 100 mg/dL for most people, and below 70 mg/dL for high-risk patients with established heart disease. HDL (high-density lipoprotein) is good cholesterol because it removes excess cholesterol from arteries and carries it to the liver for elimination. Low HDL (below 40 mg/dL) is an independent cardiovascular risk factor. Statin medications are the primary treatment for elevated LDL.
Creatinine and eGFR — Kidney Function Tests
Creatinine is a waste product from normal muscle metabolism that is filtered and excreted by the kidneys. When kidney function declines, creatinine accumulates in the blood. Normal creatinine is 0.6–1.2 mg/dL. The estimated glomerular filtration rate (eGFR) is calculated from creatinine, age, and sex, and provides a more clinically useful estimate of kidney filtering capacity. An eGFR above 60 mL/min is generally normal. Values below 60 indicate chronic kidney disease (CKD), which is staged from 1 to 5 based on eGFR. Stage 5 (eGFR below 15) indicates kidney failure requiring dialysis or transplant.
Pharmacy and Dosing Abbreviations
PRN — As Needed
From the Latin pro re nata, meaning as the situation demands. A PRN medication is taken only when a specific symptom occurs, rather than on a fixed daily schedule. Pain relievers, anti-nausea medications, and sleep aids are commonly prescribed PRN. The prescription will usually specify a maximum frequency, such as "ibuprofen 400mg by mouth every 6 hours as needed for pain." This distinguishes it from scheduled medications like blood pressure pills that must be taken daily regardless of symptoms.
BID, TID, QID, QD — Dosing Frequency
These Latin abbreviations specify how often a medication should be taken. QD (quaque die) means once daily. BID (bis in die) means twice daily, typically morning and evening. TID (ter in die) means three times daily. QID (quater in die) means four times daily. QHS means every bedtime. AC means before meals; PC means after meals. STAT means immediately. Understanding these abbreviations is essential for taking medications correctly — a QID medication missed once per day results in significantly reduced drug levels in the blood.
PO, IV, IM, SQ — Routes of Administration
PO (per os, by mouth) is the most common route — pills, tablets, capsules, or liquids swallowed orally. IV (intravenous) delivers medication directly into a vein for immediate absorption — used in hospitals for antibiotics, fluids, and emergency medications. IM (intramuscular) injection goes into muscle tissue and is absorbed faster than subcutaneous but slower than IV — used for vaccines and some antibiotics. SQ or SubQ (subcutaneous) injection goes into the fatty tissue just below the skin — used for insulin, blood thinners like enoxaparin, and many biologics.
Cardiology Terms
MI — Myocardial Infarction (Heart Attack)
A myocardial infarction occurs when blood flow to a portion of the heart muscle (myocardium) is completely blocked, usually by a ruptured atherosclerotic plaque, causing that area of muscle to die from lack of oxygen. Classic symptoms include crushing chest pain radiating to the left arm or jaw, shortness of breath, sweating, and nausea. A STEMI (ST-elevation MI) is the most severe type, showing a characteristic pattern on EKG indicating complete blockage of a major artery and requiring emergency catheterization. An NSTEMI involves partial blockage and elevated troponin levels without the ST elevation pattern.
CHF — Congestive Heart Failure
Heart failure occurs when the heart cannot pump blood efficiently enough to meet the body's needs, causing fluid to back up into the lungs (causing shortness of breath) and the legs (causing edema). CHF is classified by ejection fraction — HFrEF (heart failure with reduced ejection fraction, EF below 40%) and HFpEF (preserved EF above 50%). Symptoms include shortness of breath at rest or with minimal exertion, inability to lie flat, leg swelling, and fatigue. BNP levels are elevated in CHF and used to guide diagnosis and treatment. Management includes diuretics, ACE inhibitors, beta-blockers, and sodium restriction.
A-Fib — Atrial Fibrillation
Atrial fibrillation is the most common sustained cardiac arrhythmia, affecting over 33 million people worldwide. In A-Fib, the upper chambers of the heart (atria) fire chaotically rather than in organized beats, causing an irregular, often rapid heart rate. The most dangerous complication of A-Fib is stroke — the irregular pumping allows blood to pool and form clots in the left atrial appendage, which can break off and travel to the brain. Most patients with A-Fib require anticoagulation (blood thinners) to prevent stroke. Treatment options include rate control medications, rhythm control (cardioversion or ablation), and anticoagulation.
Emergency and Critical Care
Sepsis
Sepsis is a life-threatening medical emergency in which the body's response to an infection spirals out of control, causing widespread inflammation, organ dysfunction, and potentially death. Any infection can lead to sepsis — most commonly pneumonia, urinary tract infections, skin infections, and abdominal infections. The Sepsis-3 criteria define sepsis as infection plus acute organ dysfunction, measured by the SOFA score. Septic shock is the most severe form, characterized by dangerously low blood pressure despite fluid resuscitation. Treatment requires immediate broad-spectrum antibiotics, IV fluids, and ICU-level monitoring. Every hour of delay in antibiotic treatment significantly increases mortality.
GCS — Glasgow Coma Scale
The Glasgow Coma Scale is a standardized neurological assessment tool scoring a patient's level of consciousness from 3 (completely unresponsive) to 15 (fully awake and oriented), based on three parameters: eye opening (1–4 points), verbal response (1–5 points), and motor response (1–6 points). A GCS of 15 is normal. A GCS of 8 or below generally indicates severe brain injury and typically requires intubation to protect the airway. The GCS is used in trauma assessment, monitoring of brain injury, and determining the need for intubation. It is documented as a component score (e.g., E3V4M5 = GCS 12).
PE — Pulmonary Embolism
A pulmonary embolism occurs when a blood clot (usually originating as a deep vein thrombosis in the leg) breaks off and travels through the bloodstream to block one or more arteries in the lungs. Symptoms include sudden onset shortness of breath, chest pain that worsens with breathing, rapid heart rate, and low oxygen saturation. Large PE can cause cardiovascular collapse and death. Diagnosis is confirmed with CT pulmonary angiography (CTA chest). Treatment is anticoagulation (blood thinners) or, in massive PE with hemodynamic compromise, thrombolytics (clot-busting drugs) or surgical clot removal.
Endocrinology and Diabetes
DM1 and DM2 — Type 1 and Type 2 Diabetes
Type 1 diabetes mellitus (DM1) is an autoimmune condition in which the body's immune system destroys the insulin-producing beta cells in the pancreas. Without insulin, glucose cannot enter cells and accumulates dangerously in the bloodstream. DM1 typically presents in childhood or young adulthood and requires lifelong insulin therapy. Type 2 diabetes mellitus (DM2) is far more common, accounting for 90 to 95 percent of all diabetes cases. In DM2, cells become resistant to insulin and the pancreas cannot produce enough to compensate. DM2 is strongly associated with obesity, physical inactivity, and family history. It is managed with lifestyle changes, oral medications like metformin, and insulin when needed.
Hypoglycemia — Low Blood Sugar
Hypoglycemia is defined as blood glucose below 70 mg/dL and represents a medical emergency in people with diabetes. Symptoms include shakiness, sweating, confusion, rapid heartbeat, and fainting. Severe hypoglycemia can cause seizures, loss of consciousness, and brain damage if untreated. Treatment consists of fast-acting carbohydrates — 15 grams of glucose (juice, regular soda, glucose tablets), then rechecking blood sugar in 15 minutes. People on insulin or certain diabetes medications are at highest risk. Glucagon injections are available for severe cases where the patient cannot swallow.
Insurance and Medical Billing
EOB — Explanation of Benefits
An Explanation of Benefits is a document sent by your health insurance company after a medical claim has been processed. It is one of the most misunderstood documents in healthcare — patients frequently mistake it for a bill when it is actually an informational statement. The EOB shows the provider's billed amount, the insurance company's negotiated rate, the amount the insurance paid, and the amount you may owe as the patient. Reviewing your EOB against any subsequent bill from your provider is an important way to catch billing errors, which are surprisingly common in healthcare.
Prior Authorization and Formularies
Prior authorization (PA) is a requirement by insurance companies that your doctor obtain approval before prescribing certain medications, ordering certain tests, or performing certain procedures. The PA process requires your doctor to submit clinical documentation proving medical necessity. Denials can be appealed. A formulary is the list of drugs covered by your insurance plan, organized into tiers that determine your copay — generic drugs are on lower tiers with lower copays, brand-name drugs on higher tiers with higher copays. Understanding your formulary can save hundreds of dollars per year in medication costs.
HMO vs PPO — Insurance Plan Types
A Health Maintenance Organization (HMO) requires you to choose a primary care provider (PCP) and get referrals from your PCP before seeing specialists. HMOs typically have lower premiums and out-of-pocket costs but less flexibility. A Preferred Provider Organization (PPO) allows you to see specialists without referrals and use out-of-network providers, but at higher cost. Understanding your plan type helps you navigate referral requirements, know which providers are in-network, and estimate your expected costs before seeking care.
Mental Health Terms
MDD — Major Depressive Disorder
Major depressive disorder is a mood disorder characterized by persistent low mood, loss of interest or pleasure in activities, changes in sleep and appetite, fatigue, difficulty concentrating, and feelings of worthlessness or hopelessness, lasting at least two weeks and impairing daily function. MDD affects over 280 million people worldwide. Treatment includes psychotherapy (particularly cognitive behavioral therapy, CBT), antidepressant medications (SSRIs are first-line), and for severe cases, electroconvulsive therapy (ECT). The PHQ-9 is a standardized 9-question screening tool used to assess depression severity on a scale of 0–27.
PTSD — Post-Traumatic Stress Disorder
Post-traumatic stress disorder develops in some people following exposure to a traumatic event involving actual or threatened death, serious injury, or sexual violence. Symptoms include intrusive memories and flashbacks, nightmares, avoidance of trauma reminders, negative thoughts and feelings, and hyperarousal (being easily startled, difficulty sleeping, irritability). PTSD affects approximately 20 percent of people who experience a traumatic event. Evidence-based treatments include trauma-focused CBT, EMDR (Eye Movement Desensitization and Reprocessing), and medications including SSRIs and prazosin for nightmares.
OB/GYN Terms
LMP, EDD, and Gestational Age
LMP stands for last menstrual period — the first day of a woman's most recent period. It is the starting point for calculating gestational age and estimated due date (EDD) in pregnancy. A normal pregnancy lasts 40 weeks from the LMP. EDD is calculated as LMP plus 280 days (Naegele's rule), but early ultrasound is the most accurate way to confirm gestational age. Gestational age is expressed in weeks and days — "28 weeks and 3 days" means the pregnancy is in its 29th week. Preterm birth is defined as delivery before 37 completed weeks of gestation.
PCOS — Polycystic Ovary Syndrome
Polycystic ovary syndrome is the most common hormonal disorder in women of reproductive age, affecting 8 to 13 percent of women. PCOS is characterized by irregular or absent menstrual periods, elevated androgens (male hormones) causing acne and excess hair growth, and polycystic ovaries on ultrasound. PCOS is a leading cause of infertility and is associated with insulin resistance, obesity, type 2 diabetes, and cardiovascular disease. Treatment is individualized and may include lifestyle changes, metformin, hormonal contraceptives, and fertility medications for women trying to conceive.
Educational Reference Only. DecodeMyChart.com is provided for general informational and educational purposes only and does not constitute medical advice, diagnosis, or treatment. Normal laboratory reference ranges can vary between laboratories, patient populations, age groups, and sex. Always consult a qualified healthcare provider regarding your specific medical records, symptoms, test results, or health concerns. Do not make medical decisions based solely on information from this website.