Laboratory tests are an important diagnostic tool, but an isolated number is not a diagnosis. Results are influenced by symptoms, age, medication, food, exercise and even the time a sample is taken.
Why does “outside the range” not always mean illness?
A reference range describes values found in most people in a particular population. Statistically, some healthy people will have a result slightly outside that range. Conversely, a result within the range does not always rule out illness when symptoms or risk factors suggest otherwise. The doctor considers the overall pattern, previous results and clinical situation, not just one number. MedlinePlus: understanding laboratory test results.
Do I need to fast?
That depends on the test. Food has little effect on some tests, while for glucose, certain lipid tests or other analyses, the doctor may ask you not to eat for a set period. Drink water unless instructed otherwise. Intense exercise, alcohol and dehydration can affect several results. Do not stop medication on your own. MedlinePlus: fasting for a blood test.
Why do changes over time matter?
A small one-off abnormality may be temporary. Repeating a measurement under similar conditions helps show whether it persists. Laboratory methods and reference ranges must also be considered when comparing results. Trends are particularly important when assessing glucose, lipids, kidney, liver, thyroid and blood cell measurements. MedlinePlus: understanding laboratory test results.
Common mistakes after receiving results
Do not begin treatment or make major dietary changes based solely on an explanation found online. Repeating a wide range of tests without medical advice is also not recommended. The useful question is not just “what is abnormal?” but “does this result explain my symptoms, and does it change what we should do?”
A consultation at KIRSH
If your results are unclear or abnormal, book a medical consultation at KIRSH. Bring the results, previous tests and a medication list. If you are planning tests, the doctor can help choose investigations with a clear purpose.
Sources and further reading
This information is educational and does not replace an individual medical consultation. For acute or life-threatening symptoms, call 113.
