Blood tests explained — what markers can (and can’t) tell you.
Blood tests are often ordered, then misunderstood. This page explains the most common panels and markers in plain language, and how to think about results safely. This is educational only — not medical advice.
- Understand common panels like CBC, lipids, HbA1c, thyroid and liver/kidney markers.
- Learn what “out of range” can mean (and when it can be benign).
- See “by goal” paths: fatigue, metabolic health, inflammation, hormones and more.
Common blood test panels (high-level)
Below is a plain-language overview of what these panels typically aim to measure. The same test can be used for different clinical questions — so context matters.
| Panel | What it’s often used for | Typical markers inside | Common gotchas |
|---|---|---|---|
| CBC (Complete Blood Count) | Red/white blood cell patterns, anemia screening, infection clues | RBC, Hgb/Hct, WBC, platelets, MCV/MCH | Hydration, recent illness, and inflammation can shift values |
| Lipid panel | Cardiometabolic risk signals | Total cholesterol, LDL, HDL, triglycerides | Non-fasting vs fasting can change triglycerides |
| Glucose / HbA1c | Diabetes risk and longer-term glucose control | Fasting glucose, HbA1c | HbA1c can be affected by anemia and red cell turnover |
| Thyroid basics | Thyroid function signals | TSH, Free T4 (sometimes Free T3) | Timing, illness, and certain meds can move TSH |
| Liver markers | Liver irritation/injury pattern signals | ALT, AST, ALP, bilirubin | Hard workouts can elevate AST/ALT temporarily |
| Kidney markers | Kidney filtration and hydration context | Creatinine, eGFR, BUN | Creatinine can be influenced by muscle mass and supplements |
| CRP | Inflammation signal (non-specific) | hs-CRP or standard CRP | CRP rises with infections, injuries, and many inflammatory states |
Next step: use the “By goal” section to choose which markers are worth understanding first.
Choose a goal (how people actually use blood tests)
These are not diagnostic checklists. They are “interpretation maps” to help you understand what a clinician is usually trying to rule in/out and why repeat testing matters.
| Goal / symptom | Common starting markers | Why they’re used | What to watch for |
|---|---|---|---|
| Fatigue / low energy | CBC, ferritin/iron context, thyroid basics, B12/folate context | Anemia patterns, thyroid signals, deficiency signals | One abnormal value doesn’t explain fatigue by itself |
| Metabolic health | Fasting glucose, HbA1c, lipid panel | Longer-term glucose and cardiometabolic risk signals | Focus on trends + lifestyle + meds context |
| Inflammation / “I feel sick” | CBC differential, CRP (context), sometimes liver markers | Non-specific inflammation signals + immune cell patterns | CRP is non-specific; don’t self-diagnose infections |
| Hormone questions | Thyroid basics; sex hormones only with symptom-specific context | Many “hormone panels” are timing-sensitive | Time of day, cycle day, and meds can dominate results |
| Liver / kidney concern | ALT/AST/ALP/bilirubin; creatinine/eGFR/BUN | Pattern signals, not single-number judgments | Exercise, alcohol, dehydration can shift values |
How to prepare (simple, practical)
Many “false alarms” come from prep issues: fasting, hydration, supplements, timing, and recent training. Always follow your lab or clinician instructions first.
- Fasting: often relevant for triglycerides and fasting glucose (your provider will specify).
- Hydration: dehydration can concentrate values and affect kidney-related markers.
- Hard training: intense workouts can temporarily raise some markers (especially muscle/liver enzymes).
- Supplements: disclose common ones (iron, creatine, biotin) because they can affect certain tests.
- Timing: some hormones and cortisol-related markers vary by time of day.
Reading results safely
Reference ranges are not universal “healthy vs unhealthy” cutoffs. They are statistical ranges from a population. A result can be “out of range” for benign reasons — or “in range” while a problem exists.
| Rule of thumb | Why it matters | Example |
|---|---|---|
| Look for patterns | Single markers are noisy; patterns are more informative | Low Hgb + low MCV suggests a different story than low Hgb + high MCV |
| Compare over time | Trends are often more meaningful than one-off values | HbA1c drifting up slowly is a stronger signal than one slightly high reading |
| Context beats numbers | Symptoms, meds, infections, and training can dominate | CRP after a cold means something different than persistent CRP elevation |
Limits & common pitfalls
Blood testing is powerful, but not magic. Here’s what this site will always be strict about.
- Not diagnosis: You cannot diagnose serious disease from a generic panel alone.
- At-home constraints: finger-prick tests can differ from venous draws for some markers.
- Over-testing risk: more tests can create more false positives (noise) without clear benefit.
- Lab variation: different labs and methods can give slightly different results.
Resources and next steps
BloodTest.bio is the educational “marker map”. For the wider at-home testing ecosystem and comparisons, use the hubs below.
Disclosure: Some outgoing links may be commercial links. This does not affect our educational positioning or how topics are explained.
BloodTest.bio is for informational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional for medical decisions.