Seeing an abnormal flag on a lab result can be alarming. In practice, many flagged results turn out to be clinically insignificant — but some do warrant prompt action. This article explains how to tell the difference and what to do.
Not all flags are equal
- Normal — within the reference range. No action needed.
- Abnormal — outside the reference range. Warrants a conversation with your doctor, but is not always urgent.
- Critical — significantly outside the range and flagged by the laboratory as requiring immediate clinical review. Contact your doctor promptly.
Common reasons for a false abnormal
- Not fasting when you should have been — triglycerides and glucose are particularly sensitive to recent meals
- Strenuous exercise in the hours before the test — can elevate muscle enzymes (CK, LDH) and white blood cell counts
- Dehydration — concentrates blood values and can make results appear higher than they are
- Timing of the sample — some hormones and values vary significantly throughout the day
- Lab-to-lab variation — reference ranges differ slightly between laboratories, so a value within range at one lab may be flagged at another
When to contact your doctor immediately
- Any result flagged as Critical by the laboratory
- Symptoms that match what the numbers suggest — chest pain with elevated troponin, extreme fatigue with very low haemoglobin
- A value that is dramatically outside the range, not just borderline
- You don't understand the result and are worried — your doctor would rather take a two-minute call than have you anxious for a week
When to wait for a scheduled review
A mildly borderline result without symptoms is generally fine to discuss at your next scheduled appointment. Bring the Looms trend chart for that parameter so your doctor can see whether this is a new change or a longstanding pattern.