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Where a "normal range" comes from, and why two labs disagree
Where a "normal range" comes from, and why two labs disagree: pages on how a reference interval is actually built from the central 95% of a reference…
This launch guide maps the topic, the source base and the practical questions. Check the linked official authority before acting on a rule, deadline, price or safety requirement.
What this guide covers
Pages on how a reference interval is actually built from the central 95% of a reference population, why that guarantees one healthy result in twenty is flagged, why a twenty-item panel flags something in most healthy people, age and sex partitioning, method-dependent ranges (the same ferritin sample reported differently by two analysers), decision limits that are not reference intervals at all (cholesterol, HbA1c), paediatric and pregnancy ranges, the "optimal range" marketing claim, and how to compare an old result with a new one from a different laboratory.
Twelve pages.
How to use it
Use Where a "normal range" comes from, and why two labs disagree as a structured learning path: begin with the vocabulary, follow the evidence map, and keep the uncertainty labels attached to claims as you compare sources.
The page keeps the main question, its evidence base and its limits together in one canonical place. That makes it useful as a quick orientation and avoids splitting a broad subject into shallow pages before each narrower answer has enough verified material of its own.
Search vocabulary in four languages
Terminology changes across borders. These are example phrases people use for the same subject in Estonian, Finnish, Russian and English; they are included as a practical vocabulary aid, not as hidden keywords.
| Language | Example phrase |
|---|---|
| Estonian | referentsväärtused miks laborites erinevad |
| Finnish | viitearvot miksi eri laboratorioissa erilaiset |
| Russian | почему референсные значения разные в лабораториях |
| English | why do lab reference ranges differ |
Evidence and provenance
The evidence map below records the primary, official or openly licensed material chosen for this guide. It is deliberately visible so a reader can tell the difference between a rule published by an authority, a measured dataset and an editorial explanation.
Source: own writing; the laboratories' own public test directories (SYNLAB Eesti, HUSLAB, Fimlab) for the worked comparisons; CLSI EP28 and IFCC traceability described and cited, not reproduced. · checked 2026-09-09
Source names are preserved even where an authority changes its web address. No figure is added to this launch page unless it is already present in the cited source description or can be computed from a named dataset.
Scope and boundaries
/blood-test lists the ranges themselves; this explains where they come from and interprets no one's result.
Connected TempoLife guides
The following paths are the intentional hand-offs named in the brief. They keep adjacent subjects separate while making the next useful reference easy to find.
Blood Test
Continue to the related TempoLife reference.
Labs
Continue to the related TempoLife reference.
Why it belongs on TempoLife
/blood-test, /labs.
Frequently asked questions
What does this guide cover?
Pages on how a reference interval is actually built from the central 95% of a reference population, why that guarantees one healthy result in twenty is flagged, why a twenty-item panel flags something in most healthy people, age and sex partitioning, method-dependent ranges (the same ferritin sample reported differently by two analysers), decision limits that are not reference intervals at all (cholesterol, HbA1c), paediatric and pregnancy ranges, the "optimal range" marketing claim, and how to compare an old…
What evidence does it use?
own writing; the laboratories' own public test directories (SYNLAB Eesti, HUSLAB, Fimlab) for the worked comparisons; CLSI EP28 and IFCC traceability described and cited, not reproduced.
Where does this guide stop?
/blood-test lists the ranges themselves; this explains where they come from and interprets no one's result.
Turn the reference into a routine
TempoLife brings food, movement, sleep and everyday health habits into one private place when you want to track what happens next.