A reference range shows where 95 percent of a healthy reference population sits for that biomarker. It is the most common way to interpret a blood test result, but the range is not a personal 'normal' line and can differ between labs.
Where reference ranges come from
Ranges are based on testing a reference population (often thousands of healthy adults) and capturing the middle 95 percent. This means roughly 5 percent of healthy people will naturally fall outside the range. An out-of-range result is information, not necessarily a problem.
Why ranges differ between labs
Different assays (the technology used to measure the marker) can produce slightly different absolute values. NHS and private labs may use different equipment. A ferritin reading of 35 ng/mL on one assay may correspond to a slightly different number on another. This is why your report always shows the range from the specific lab that ran your test.
Reference range vs optimal range
Reference ranges show where healthy people sit. Some clinicians and researchers also discuss 'optimal' ranges, which may be tighter and based on outcomes data. For example, vitamin D above 50 nmol/L is the NHS 'adequate' threshold; many practitioners aim for 75 to 125 nmol/L for broader health.
Reading your Chxhealth report
Your report shows the range used by our lab partner. Out-of-range results are flagged with guidance to discuss with a healthcare professional. Chxhealth is a biomarker and genetic data provider. We do not diagnose, treat or prescribe. Our service supports your wellbeing journey alongside your healthcare professional.
Frequently asked questions
Is my result good if it is in range?
Generally yes, but in range does not always mean optimal. Some markers (vitamin D, ferritin, certain hormones) have meaningful sub-ranges within the broad reference range.
Why does my Chxhealth range differ from a previous test?
Different labs use different assays which produce slightly different absolute values. Trends within one lab over time are more comparable than absolute values across different labs.
About this article. Educational content. Chxhealth is a biomarker and genetic data provider. We do not diagnose, treat or prescribe. Our service supports your wellbeing journey alongside your healthcare professional. For medical advice about your health or results, please speak to a qualified clinician.
