Medical Terms Explained

Why Medical Documents Are Written in Jargon

If you've ever received a letter from a hospital, a set of blood test results, or a discharge summary after a procedure, you've probably been struck by how impenetrable the language is. Medical terminology isn't designed to exclude patients — it evolved over centuries as a precise international language that allows healthcare professionals worldwide to communicate without ambiguity.

Much of medical vocabulary comes from Latin and Greek roots. These roots were adopted by European universities during the Middle Ages as the common language of scholarship, and medicine retained them long after other fields moved on. The result is a vocabulary that is deeply logical once you know the building blocks — but entirely opaque if you don't.

There is a secondary reason too: precision. In medicine, vague language can be dangerous. A word like "high" means different things in different contexts. Medical terms like "hyperglycaemia" or "tachycardia" carry specific, unambiguous meanings that leave no room for misinterpretation between healthcare providers — even across language barriers.

Common Medical Prefixes and Suffixes

Learning a handful of common Latin and Greek roots allows you to decode a surprisingly large portion of medical vocabulary. Most medical terms are built from a prefix (beginning), a root (middle), and a suffix (ending). Once you know these building blocks, unfamiliar terms become much less frightening.

Common Prefixes

• Hyper-: Too much / above normal (e.g., hypertension = high blood pressure, hyperglycaemia = high blood sugar)
• Hypo-: Too little / below normal (e.g., hypotension = low blood pressure, hypoglycaemia = low blood sugar)
• Brady-: Slow (e.g., bradycardia = slow heart rate)
• Tachy-: Fast (e.g., tachycardia = fast heart rate)
• Intra-: Within (e.g., intravenous = within a vein)
• Peri-: Around (e.g., pericardium = membrane around the heart)
• Pre-: Before (e.g., pre-operative = before surgery)
• Post-: After (e.g., post-operative = after surgery)
• Sub-: Under / below (e.g., subcutaneous = under the skin)
• Anti-: Against (e.g., antibiotic = against bacterial life)

Common Suffixes

• -itis: Inflammation (e.g., appendicitis = inflammation of the appendix)
• -ectomy: Surgical removal (e.g., appendectomy = removal of the appendix)
• -ology: The study of (e.g., cardiology = study of the heart)
• -ologist: A specialist in the study of (e.g., cardiologist = heart specialist)
• -plasty: Surgical repair or reconstruction (e.g., rhinoplasty = nose reshaping)
• -scopy: Visual examination (e.g., endoscopy = examination inside the body)
• -pathy: Disease or disorder (e.g., neuropathy = nerve disease)
• -algia: Pain (e.g., neuralgia = nerve pain)
• -oma: Tumour or swelling (e.g., carcinoma = cancerous tumour)
• -rrhea: Flow or discharge (e.g., diarrhoea = abnormal intestinal discharge)

Understanding Lab Results

Blood tests and other lab results are among the most commonly misunderstood medical documents. They typically consist of a table of values with columns for the test name, your result, and a reference range. The reference range (sometimes called "normal range") shows the values that the majority of healthy adults fall within.

A result outside the reference range is flagged — usually with an "H" (high) or "L" (low), or highlighted in bold or red. It is important to understand that being slightly outside a reference range does not necessarily indicate a problem. Reference ranges are statistical — they represent the middle 95% of healthy people, which means 5% of healthy people will have at least one value outside the normal range on any given day.

Your doctor considers your results in the context of your age, sex, medical history, symptoms, and other test results — not in isolation. A slightly elevated value that has been stable for years is very different from a value that has rapidly increased or is significantly outside range.

Blood Test Values Explained

Here are the most common blood tests and what they measure:

• Full Blood Count (FBC / CBC): Measures red blood cells (carry oxygen), white blood cells (fight infection), haemoglobin (protein in red blood cells), and platelets (help clotting). Useful for detecting anaemia, infection, and blood disorders.
• HbA1c: Average blood sugar level over the past 2–3 months. Used to diagnose and monitor diabetes. Expressed as a percentage or mmol/mol.
• Cholesterol panel: Measures total cholesterol, LDL ("bad") cholesterol, HDL ("good") cholesterol, and triglycerides. Used to assess cardiovascular risk.
• Liver function tests (LFTs): Measure enzymes and proteins produced by the liver (ALT, AST, ALP, GGT, bilirubin, albumin). Elevated enzymes can indicate liver stress or damage.
• Renal function / U&Es: Urea and electrolytes, including creatinine and eGFR. Creatinine is a waste product filtered by the kidneys; elevated levels or a low eGFR (estimated glomerular filtration rate) can indicate reduced kidney function.
• Thyroid function (TSH, T4): TSH (thyroid-stimulating hormone) is the primary screening test for thyroid disorders. High TSH suggests an underactive thyroid (hypothyroidism); low TSH suggests overactive (hyperthyroidism).
• Ferritin / iron studies: Measure iron stores. Low ferritin indicates iron deficiency, a common cause of tiredness and anaemia.
• CRP (C-reactive protein): A marker of inflammation. Elevated CRP can indicate infection, inflammatory conditions, or tissue injury.

Reading a Diagnosis

A diagnosis in a medical letter or discharge summary is often written using clinical terminology that sounds alarming but may have a quite straightforward meaning. Some examples:

• Benign: Not cancerous, not life-threatening in itself (e.g., "benign prostatic hyperplasia" = non-cancerous enlargement of the prostate).
• Malignant: Cancerous; capable of spreading.
• Acute: Sudden onset; short duration. Not necessarily serious — "acute" refers to timing, not severity.
• Chronic: Long-lasting or recurring. Again, this is about duration, not severity.
• Idiopathic: No known cause has been identified.
• Bilateral: Affecting both sides (e.g., bilateral knee pain = pain in both knees).
• Unilateral: Affecting one side only.
• Differential diagnosis: A list of possible diagnoses the doctor is considering based on your symptoms — not a final conclusion.
• Rule out: The doctor wants to exclude a possible diagnosis through further testing.

Prescription Abbreviations

Prescriptions are traditionally written using Latin abbreviations for dosing instructions. While many modern prescriptions now use plain English, you may still encounter these:

• od (omni die): Once daily.
• bd (bis die): Twice daily.
• tds (ter die sumendum): Three times daily.
• qds (quater die sumendum): Four times daily.
• prn (pro re nata): As needed / when required.
• stat: Immediately / straight away.
• ac (ante cibum): Before food.
• pc (post cibum): After food.
• nocte: At night.
• PO (per os): By mouth (orally).
• IV (intravenous): Into a vein.
• IM (intramuscular): Into a muscle.
• SC (subcutaneous): Under the skin.

When to Ask Your Doctor

Understanding medical terminology is a tool for comprehension — it is not a substitute for professional medical advice. There are several situations where you should always speak directly with a healthcare professional rather than relying on self-interpretation:

• Any result flagged as significantly abnormal by the laboratory.
• A new diagnosis, especially one involving the words "malignant," "cancer," or any unfamiliar condition.
• Changes to your medication, particularly if you don't understand why the change was made.
• Any symptom that is new, worsening, or worrying you, regardless of whether your test results look normal.
• When you're unsure whether a recommended treatment or procedure is appropriate for you.

You are always entitled to ask your doctor to explain things in plain language — and most doctors will welcome the question. If you receive a document you don't understand and can't immediately speak with a professional, understanding the terminology through a guide or AI tool can help you formulate better questions.

Using AI for Medical Document Comprehension

AI tools like Simplifier can be genuinely useful for understanding the language in medical documents. If you've received a hospital discharge letter full of abbreviations, or a set of blood results you don't know how to interpret, Simplifier can translate the terminology into plain English and give you a clear sense of what each value or term means.

This kind of comprehension support is particularly valuable for:

• Understanding what tests have been requested and why.
• Decoding the meaning of a diagnosis before your next appointment.
• Preparing specific, informed questions to ask your doctor.
• Understanding the dosing instructions on a prescription.
• Making sense of a medical letter written for another professional, not for you.

Simplifier does not provide medical advice, and AI output should never replace a consultation with your doctor. But arriving at an appointment having already understood the terminology — and knowing what questions to ask — is a real advantage. For the step-by-step guide, see How to Simplify Medical Documents.