How to read your blood test results

To read blood test results, start with the three columns that matter: the marker name, your value with its unit, and the lab's reference range beside it. Anything outside the range is usually flagged with an H (high), an L (low) or an asterisk. That flag is a prompt for a doctor to look more closely, not a verdict on your health.

Most people now see their results online before they see a doctor, sometimes late at night, sometimes with a flag they were not expecting. This guide is for that moment. It will not interpret your result for you, but it will help you understand what you are looking at and arrive at your consult with better questions.

The layout of a pathology report

Australian pathology reports follow a broadly similar layout, whichever lab produced them.

• Header. Your details, the requesting doctor, the date and time the sample was collected, and the date it was reported. Collection time matters for hormones, which we will come back to.
• Test groups. Results are grouped by the request: hormone panel, thyroid function, iron studies and so on. Each group may sit on its own page.
• Result lines. One line per marker: name, your value, the unit, the reference range, and a flag if you fall outside it.
• Comments. Many reports include a short note from the lab, either a standard explanation of the reference range (for example that it applies to a particular cycle phase) or a comment on your specific result. These are worth reading; they are written by pathologists and often answer the obvious question.
• Cumulative view. If you have had the same test before at the same lab, some reports show previous results beside the new one, which is often more useful than any single figure.

Our sample report page shows how a KnowLuna report is laid out with each of these parts labelled.

Units: why the same marker can look different

Markers are reported in the unit the lab uses, and it is not always the one you saw online. Oestradiol may be reported in pmol/L in Australia but in pg/mL on many overseas websites; vitamin D in nmol/L here versus ng/mL elsewhere; haemoglobin in g/L here versus g/dL in some countries. The numbers differ by a conversion factor, so a value that looks alarmingly high or low compared with something you read may simply be in a different unit. Always compare your value with the range printed next to it, not with a range from somewhere else.

The reference range and what the flag means

The reference range is the interval within which most results from a defined healthy population fall, for that lab, on that analyser. By design, a small proportion of perfectly healthy people fall outside it for any given marker. The more markers on your report, the more likely it is that at least one lands just outside its range by chance.

So a flag means "this is outside the interval we expect for most people". It does not mean "this is abnormal for you". A doctor weighs how far outside the range the value sits, whether it fits your symptoms, whether it matches previous results, and whether the range even applies to your situation. We go deeper in our article on reference ranges.

Context that changes how a result is read

The same number can mean different things depending on what was happening when the blood was drawn. Things that matter most for the tests KnowLuna offers:

• Cycle day. FSH, LH, oestradiol and progesterone move dramatically across the menstrual cycle. A report may print a range for each phase; make sure you know which day you were on. The day 3 hormone test article explains why timing matters.
• Hormonal contraception. The pill, ring, implant and hormonal IUD suppress or alter several of the markers on a hormone panel, so results are read with that in mind.
• Time of day. Cortisol, testosterone and iron all vary through the day. Morning collection is standard for these.
• Fasting. Glucose and insulin need a fasting sample, and lipids are often collected fasting too. A non-fasting result is not wrong, but it is read against different expectations.
• Illness, pregnancy and medicines. A recent viral illness can move thyroid and iron markers; pregnancy changes almost everything; supplements such as biotin can interfere with some hormone assays.

Reading a pattern, not a single line

Doctors rarely read one marker in isolation. On a thyroid report, TSH is read alongside free T4. On iron studies, ferritin is read alongside transferrin saturation and, if available, an inflammation marker, because ferritin rises with inflammation even when iron stores are low. On a hormone panel, FSH is read against oestradiol and the cycle day, because a "high" FSH on day 3 means something different from a high FSH around ovulation.

If you take one thing from this article, let it be that: the story is in the combination. A single flagged marker is the least informative thing on the page.

What to ask your doctor

Whether you see your own GP or a KnowLuna doctor, these questions make a results consult more useful:

• Which results matter for what I came in about, and which are incidental?
• Does the reference range on this report apply to my age and cycle phase?
• Is anything here worth repeating, and if so, when and under what conditions?
• How does this compare with my previous results?
• What would change your interpretation: a symptom, another test, a different cycle day?

Common questions

General information only, not medical advice. If your symptoms are severe or sudden, see a doctor promptly.