Blood Tests Explained: Which Test Checks for What
Your doctor ordered a blood test — but what does each one actually check? A clear guide to the common blood tests, what they look for, and why they matter, so you understand your own health better.
Your doctor says "let's do some blood tests" and hands you a form full of abbreviations — CBC, LFT, KFT, TSH, HbA1c, lipid profile. Most people get the tests done with no idea what each one checks. Understanding the common blood tests — what they look for and why — helps you take part in your own health rather than just handing over an arm. This is a clear, plain-language guide to which test checks for what. It is general education; your doctor decides which tests you actually need and interprets the results for you.
The Most Common Blood Tests, Decoded
| Test | What it checks | Often used for |
|---|---|---|
| CBC (Complete Blood Count) | Red cells, white cells, platelets, haemoglobin | Anaemia, infection, general health |
| Blood sugar (fasting / HbA1c) | Glucose now, and average over ~3 months | Diabetes, prediabetes |
| Lipid profile | Cholesterol (LDL, HDL) and triglycerides | Heart-disease risk |
| LFT (Liver Function Test) | Enzymes and proteins from the liver | Liver health, jaundice, fatty liver |
| KFT / RFT (Kidney Function) | Creatinine, urea, eGFR | Kidney health |
| Thyroid (TSH, T3, T4) | Thyroid hormone levels | Under/overactive thyroid |
| Vitamin D / B12 | Levels of these vitamins | Fatigue, bone health, nerve symptoms |
| Iron studies | Iron stores (ferritin, etc.) | Iron-deficiency anaemia |
| CRP / ESR | Markers of inflammation | Infection, inflammation |
Grouped by "Why It's Ordered"
Another way to think about it — what a doctor might order for common concerns:
- Feeling tired / weak? CBC (anaemia), thyroid, vitamin D/B12, blood sugar
- Diabetes check? Fasting sugar and HbA1c
- Heart-disease risk? Lipid profile, blood sugar, sometimes others
- Liver concern (e.g. fatty liver, jaundice)? LFT
- Kidney check (e.g. with high BP or diabetes)? KFT/RFT
- Thyroid symptoms (weight, mood, periods, energy)? TSH first
- General health check-up? Often a bundle: CBC, sugar, lipids, LFT, KFT, thyroid
Getting a Blood Test Done
- Some tests need fasting (usually 8–12 hours, water allowed) — like fasting sugar and often lipids; your doctor/lab will tell you
- Many, like HbA1c, thyroid, and CBC, don't need fasting
- Tell the lab about medicines or supplements you take, as some affect results
- The blood draw itself takes a minute; results often come back within a day
Reading Your Report
Reports show your value next to a reference range (the normal band), often flagging highs/lows. But a value slightly outside the range is not always a problem, and a "normal" result does not always rule things out — results must be read in the context of you: your symptoms, history, and other results. That interpretation is the doctor's job. Resist the urge to panic-diagnose from a single flagged number. (See our detailed guides on the CBC report, diabetes tests, and kidney function tests.)
When to See a Doctor
A doctor should decide which tests you need and interpret the results — that context is everything. See a doctor to discuss symptoms that might warrant testing, or to go over results you don't understand or that came back abnormal. An online consultation is ideal for exactly this: talk through your symptoms, get the right tests ordered, then review the report together and understand what it means for you — without guessing from internet ranges. Knowing what each test checks helps you be an informed partner in your care. (See our guides on preventive check-ups and health checks by age.)