Thriva, Medichecks or a GP panel: what your nutritional markers mean (UK)

This entry is part of the Nutri Tailor Health Reference Library — cited research on supplements, nutrients and adjacent areas of health.

Summary

A home or GP blood panel gives you numbers and a flag against the laboratory's range, which tells you whether you sit outside that range and nothing more. This page reads the nutritional markers the way UK guidance does: ferritin below 30 is iron deficiency even when unflagged; B12 between 180 and 350 is indeterminate, not fine; vitamin D below 50 is insufficient; folate below 3 is deficient; TSH is read with free T4; the HbA1c bands are 42 and 48; and hs-CRP explains a misleading ferritin. The free interpreter reads results against these thresholds. Anything outside the range on a full blood count, liver or kidney panel is a GP conversation, not a supplement.

How it works

A laboratory flags a result against its own reference range, which is the middle 95 percent of the people that laboratory tested, not a statement about what is right for you. Ranges differ between laboratories, some start below the guideline thresholds, and a single result is a snapshot that inflammation, time of day or a recent meal can move. Reading a panel well means reading each marker against the UK guideline threshold, in the right units, and looking at the pattern across markers rather than any one number.

Guideline positions

Read each marker against the UK threshold, not the laboratory flag. Ferritin: below 30 micrograms per litre is iron deficiency even when unflagged, and CRP alongside it shows whether inflammation is hiding a low result; the full iron panel adds transferrin saturation. B12: below 180 ng/L is deficient and 180 to 350 is indeterminate, and total and active B12 are read against different ranges. Folate: below 3 micrograms per litre is deficient. Vitamin D: below 25 nmol/L is deficient and 25 to 50 insufficient. TSH is read together with free T4. HbA1c has bands at 42 and 48. MCV on the full blood count points to iron when low and to B12 or folate when high. The omega 3 index is read where it was tested, and serum magnesium misses most deficiency.

Practical framework

Enter the results into the free blood test result interpreter, which reads them against these thresholds. Anything outside the range on a full blood count, liver or kidney panel is a GP conversation, not a supplement. For the whole picture over time, an app that reads the report itself goes further than any page can.

Common misconceptions

A result inside the range can still be low for you, such as a ferritin of 35 with symptoms. A result outside the range can be nothing, such as a ferritin raised by a cold. The pattern matters more than any one number, which is what the free blood test result interpreter reads, and for the whole picture over time, an app that reads the report itself.

Sources

2021. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut. PMID: 34497146 · DOI: 10.1136/gutjnl-2021-325210
2024. Vitamin B12 deficiency in over 16s: diagnosis and management (NG239). National Institute for Health and Care Excellence (NICE).
Anaemia - iron deficiency. NICE Clinical Knowledge Summaries (CKS).
Anaemia - B12 and folate deficiency. NICE Clinical Knowledge Summaries (CKS).
2016. SACN Vitamin D and Health report. Scientific Advisory Committee on Nutrition (SACN, UK government).
Vitamin D: supplement use in specific population groups (PH56). National Institute for Health and Care Excellence (NICE).
Heavy menstrual bleeding: assessment and management (NG88). National Institute for Health and Care Excellence (NICE).
Verdon F, Burnand B, Stubi CL, Bonard C, Graff M, Michaud A, Bischoff T, de Vevey M, Studer JP, Herzig L, Chapuis C, Tissot J, Pécoud A, Favrat B 2003. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ. PMID: 12763985 · DOI: 10.1136/bmj.326.7399.1124
Houston BL, Hurrie D, Graham J, et al 2018. Efficacy of iron supplementation on fatigue and physical capacity in non-anaemic iron-deficient adults: a systematic review of randomised controlled trials. BMJ Open. PMID: 29626044 · DOI: 10.1136/bmjopen-2017-019240

Back to Blood markers overview