Glossary term

LOQ (Limit of Quantitation)

Also known as: LOQ, limit of quantitation, limit of quantification

Part of: How to read a report

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3 min read
Last reviewed
Last reviewed January 1970
Reading level
Written in plain English
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Reviewed by Medipher Editorial Team

The smallest amount of a substance a test can measure with acceptable precision, as opposed to merely detect.

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Medipher explains medical wording in plain English — it does not diagnose or replace a clinician. If this is a medical emergency, call your local emergency number immediately.

What is this?

Detecting that something is present and measuring exactly how much are different problems. The limit of quantitation is the lowest amount a method can measure with acceptable accuracy.

A result sitting between the limit of detection and the limit of quantitation may be reported as detected but not quantifiable — the test can see it, but cannot put a trustworthy number on it.

Both limits belong to the method used, so they vary between laboratories and can change if a laboratory changes its equipment.

Why is it important?

Between the detection and quantitation limits, a test can tell that something is there but not reliably say how much.

Where you'll see it: Drug-level, viral-load and other quantitative specialist reports.

Does an abnormal result always mean something is wrong?

Not necessarily. A number that sits outside the printed range is a prompt for interpretation — not a diagnosis.

  • A single result rarely gives the full picture — clinicians interpret it alongside your symptoms.
  • Your medical history, medications and other blood tests all shape the meaning of one value.
  • Small movements just outside the reference range are common and often not concerning.
  • Repeat testing over time is frequently more useful than any single number.

What might happen next?

  • Use the limits printed on your own report when comparing results over time.
  • Ask the requesting service whether a change is meaningful given those limits.

One result rarely tells the whole story. Clinicians look at your symptoms, medical history, medications and other tests together — and a single value that sits slightly outside the reference range is often normal for you. Repeat testing over time is frequently more useful than any one number. Medipher helps you understand what a result means in plain English, but it cannot diagnose medical conditions or replace advice from a doctor, nurse or pharmacist.

When should I speak to a healthcare professional?

Speak with your GP or another healthcare professional if:

  • You've been asked to repeat the test.
  • You're experiencing new or worsening symptoms.
  • Your clinician has flagged the result as needing follow-up.
  • You don't understand your results or feel unsure what to do next.

If you have severe symptoms — chest pain, severe breathlessness, fainting, heavy bleeding or feel very unwell — seek urgent help. If this is a medical emergency, call your local emergency number immediately. Medipher is designed to help explain medical information and is not an emergency service.

Frequently asked questions

Related blood tests

Terms clinicians often look at alongside LOQ (Limit of Quantitation).

Related guides

Still unsure what your result means?

This page explains one medical term. If you have a blood test, GP letter or hospital report, Medipher can explain your entire document in plain English.

  • what your results mean
  • unfamiliar medical terminology
  • what your clinician may be monitoring
  • useful questions to ask at your next appointment

Sources

General patient information referenced when writing this page.

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About this page

Medical reviewer
Clinical review pending
Last reviewed
January 1970
Last updated
January 1970

Evidence. Written from public patient-information sources including the NHS, NICE and the Association for Laboratory Medicine, and reviewed for plain-English accuracy before publication.

Educational content only. Medipher explains medical language in plain English. It does not diagnose, and it is not a substitute for advice from a doctor, nurse or pharmacist. Read the medical disclaimer.

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This glossary entry is general health information, not medical advice. Medipher explains medical wording in plain English and does not diagnose, provide treatment advice, or replace a GP, doctor, nurse or pharmacist. Always discuss your results with a qualified clinician.