DecodeMyChart — Medical Abbreviation Reference
Plain-English definitions for medical abbreviations, acronyms, and lab values. Free reference for patients, caregivers, and students.
General Medical Terms
SOB — Shortness of Breath
Difficulty breathing or feeling breathless. A very common symptom documented in charts to describe respiratory complaints. Patients presenting with SOB may have conditions ranging from anxiety and asthma to heart failure and pulmonary embolism.
CC — Chief Complaint
The primary reason the patient is seeking medical care, usually recorded in the patient's own words. The chief complaint is the starting point of every clinical encounter and guides the entire diagnostic workup.
Dx — Diagnosis
The medical identification of a disease or condition based on symptoms, exam findings, and test results. A diagnosis is the conclusion reached after evaluating all available clinical information.
Tx — Treatment
The medical management plan for a patient's condition, which may include medications, procedures, lifestyle changes, or referrals to specialists.
Hx — History
The patient's medical background including past illnesses, surgeries, hospitalizations, and family history relevant to current care.
NPO — Nothing by Mouth
From the Latin nil per os, meaning the patient must not eat, drink, or take anything by mouth. Typically required before surgery, certain procedures, or when the bowel needs to rest.
DNR — Do Not Resuscitate
A medical order indicating that if the patient's heart stops or they stop breathing, no CPR or resuscitation efforts should be performed. This is a legally binding order based on the patient's wishes.
WNL — Within Normal Limits
A shorthand indicating that a test result, exam finding, or measurement falls within the expected normal range. Commonly used in physical exam documentation.
Lab Values and Normal Ranges
CBC — Complete Blood Count
A blood test measuring red blood cells, white blood cells, hemoglobin, hematocrit, and platelets. One of the most commonly ordered lab tests used to screen for anemia, infection, and blood disorders.
WBC — White Blood Cell Count (Normal: 4.5–11.0 K/uL)
Measures infection-fighting cells in the blood. A high WBC (leukocytosis) often signals infection or inflammation. A low WBC (leukopenia) may indicate viral illness, bone marrow problems, or immune suppression.
Hgb — Hemoglobin (Normal: 11.5–17.5 g/dL)
The protein in red blood cells that carries oxygen throughout the body. Low hemoglobin indicates anemia, which causes fatigue, pallor, and shortness of breath. Common causes include iron deficiency, vitamin B12 deficiency, and chronic disease.
HbA1c — Hemoglobin A1c (Normal: 4.0–5.7%)
A blood test reflecting average blood sugar levels over the past 2 to 3 months. Used to diagnose and monitor diabetes. A result of 5.7 to 6.4 percent indicates prediabetes; 6.5 percent or above indicates diabetes.
TSH — Thyroid-Stimulating Hormone (Normal: 0.4–4.0 mIU/L)
A pituitary hormone that regulates thyroid function. A high TSH suggests an underactive thyroid (hypothyroidism) causing fatigue and weight gain. A low TSH suggests an overactive thyroid (hyperthyroidism) causing weight loss and rapid heartbeat.
Cr — Creatinine (Normal: 0.6–1.2 mg/dL)
A waste product from muscle metabolism filtered by the kidneys. Elevated creatinine is a key indicator of reduced kidney function. Rising creatinine over several days is more concerning than a single elevated value.
INR — International Normalized Ratio (Normal: 0.8–1.1)
A standardized measure of how long blood takes to clot. Used primarily to monitor warfarin (blood thinner) therapy. Therapeutic range for warfarin patients is usually 2.0 to 3.0. Values above 3.5 significantly increase bleeding risk.
LDL — Low-Density Lipoprotein (Normal: under 100 mg/dL)
Known as bad cholesterol. High LDL increases the risk of plaque buildup in arteries, leading to heart attack and stroke. Lifestyle changes and statin medications are the primary treatments for elevated LDL.
eGFR — Estimated Glomerular Filtration Rate (Normal: 60–120 mL/min)
An estimate of how well the kidneys are filtering blood. A result below 60 mL/min indicates chronic kidney disease. The lower the number, the less kidney function remains. Below 15 typically requires dialysis or a kidney transplant.
Pharmacy and Dosing Terms
PRN — As Needed
From the Latin pro re nata, meaning as the thing is needed. Medication is taken only when symptoms occur rather than on a fixed daily schedule. For example, a pain medication prescribed PRN is taken only when pain is present.
BID — Twice Daily
Medication taken two times per day, typically morning and evening, roughly 12 hours apart. Common examples include many antibiotics and blood pressure medications.
QD — Once Daily
Medication administered once every 24 hours. Many chronic disease medications such as statins, blood pressure pills, and thyroid medications are prescribed once daily.
IV — Intravenous
Medication or fluids delivered directly into a vein through a needle or catheter, allowing for the most rapid absorption into the bloodstream. Used in hospitals for antibiotics, fluids, pain medications, and many other treatments.
Cardiology Terms
MI — Myocardial Infarction
A heart attack, occurring when blood flow to part of the heart muscle is blocked long enough to cause permanent damage. Symptoms include chest pain, shortness of breath, and pain radiating to the arm or jaw. A medical emergency requiring immediate treatment.
HTN — Hypertension
High blood pressure, defined as consistently elevated blood pressure readings above 130 over 80 mmHg. A major risk factor for heart attack, stroke, and kidney disease. Often called the silent killer because it has no symptoms.
A-Fib — Atrial Fibrillation
An irregular, often rapid heart rhythm originating in the upper chambers of the heart. Significantly increases the risk of stroke. Treated with rate control medications, blood thinners, and sometimes cardioversion or ablation.
CHF — Congestive Heart Failure
A condition where the heart cannot pump blood efficiently, causing fluid to back up into the lungs and body tissues. Causes shortness of breath, leg swelling, and fatigue. Managed with diuretics, ACE inhibitors, and beta-blockers.
Insurance and Billing Terms
EOB — Explanation of Benefits
A document sent by your insurance company after a medical claim is processed. It shows what was billed, what your insurance paid, and what you may owe. An EOB is not a bill — it is an informational statement showing how your claim was processed.
OOP — Out of Pocket
The amount you pay directly for healthcare costs not covered by insurance, including deductibles, copays, and coinsurance. Once you reach your annual out-of-pocket maximum, your insurance covers 100 percent of remaining covered costs.
PA — Prior Authorization
Approval required from your insurance company before certain medications, procedures, or specialist visits are covered. Your doctor submits clinical documentation to justify medical necessity. Denial of a prior authorization can be appealed.
Educational reference only. This site is for informational purposes and does not constitute medical advice. Always consult a qualified healthcare provider regarding your specific medical situation. Normal lab ranges can vary between laboratories and patient populations.