What does "your blood tests are normal" actually mean?

My dad had his first heart attack at 54, and then a triple bypass. His cholesterol had always been low. It didn’t protect him. This year, his doctors started him on a statin.

That’s what his story taught me about “normal”: one number isn’t your heart risk.

Cholesterol travels in lipoproteins; LDL is the vehicle. Too many of those vehicles, for too many years, drives plaque, so LDL is a cause, not a bystander (Ference 2017). In trials, lowering LDL cut heart attacks and strokes (CTT 2010). It also did so in people with no heart disease yet (Taylor 2013, Cochrane). So a low result is better than a high one. But one number isn’t your heart risk. The pattern is: ApoB or non-HDL, blood pressure, blood sugar, smoking, family history and age.

I don’t know which parts of that pattern drove my dad’s heart disease, and I’m not going to guess. What I took from it is that a single “normal” result, even a good one, doesn’t tell you that you’re safe. That’s a large part of why, after nearly forty years working with people, I still ask what a normal result is actually telling you.

Sources for this section: Ference BA et al. Low-density lipoproteins cause atherosclerotic cardiovascular disease. Eur Heart J 2017;38:2459–72. PMID 28444290. doi:10.1093/eurheartj/ehx144 · Cholesterol Treatment Trialists’ (CTT) Collaboration, Baigent C et al. Efficacy and safety of more intensive lowering of LDL cholesterol. Lancet 2010;376:1670–81. PMID 21067804. doi:10.1016/S0140-6736(10)61350-5 · Taylor F et al. Statins for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev 2013;(1):CD004816. PMID 23440795. doi:10.1002/14651858.CD004816.pub5

What a reference range actually is

When your GP says a result is “normal”, it means it falls inside the lab’s reference range. Labs build those ranges from groups of people they treat as healthy, and take the middle 95%. That has two consequences. One in twenty healthy people will fall outside the range on any single test. And a result inside the range isn’t a promise that it’s right for you.

For a few markers, experts now argue the lower limit is set too low. Ferritin is the clearest example: many UK labs flag it only below about 12–15 µg/L (12–15 ng/mL), but the British Society of Gastroenterology reads below 15 µg/L (15 ng/mL) as absent iron stores and below 30 µg/L (30 ng/mL) as low iron stores (BSG 2021). In adults seeing a doctor, below 30 µg/L picked out iron deficiency with 79% sensitivity and 98% specificity, on low-certainty evidence (Garcia-Casal 2021, a Cochrane review); in anaemic patients, 30 µg/L or below identified it well (Mast 1998). The American Society of Hematology’s 2026 guideline uses 30 µg/L as its cut-off whether or not you’re anaemic, on low-certainty evidence (ASH 2026).

So “normal” isn’t wrong. It’s a screen for disease, and it answers a narrower question than “is this right for me?”

Lab range, my working target, and what each is based on

I use working targets for some markers. They’re mine, and I label them that way. Where there’s a trial or a guideline behind one, I say which; where there isn’t, I say that too.

What a standard GP panel usually doesn’t include

A typical NHS panel checks blood count, kidney and liver function, TSH and cholesterol. It’s built to catch disease that needs treatment. It often doesn’t include fasting insulin, Free T3, a full iron panel, homocysteine, magnesium or zinc. None of these is exotic; they’re just outside a disease screen.

Fasting insulin is the one I’d most like people to know about. In a long-running study of British civil servants, insulin sensitivity fell steeply in the five years before diabetes was diagnosed, while fasting glucose rose sharply only in the last three (Tabák 2009). A normal glucose can hide a body working harder to keep it there.

Why your GP isn’t to blame

I want to be clear about this, because it matters. GPs are working within a system that is designed for disease management, not optimal health. They have 10-minute appointments, NHS reference ranges, and clinical guidelines that govern what they can test and prescribe. Most GPs I know are thoughtful, caring professionals who are doing their best within significant structural constraints.

The gap isn't usually incompetence. It's a difference in what the system is built to look for. Conventional medicine is designed to answer "does this person have a diagnosable disease?" I’m asking a different question: why does this person feel the way they do, and what’s worth checking next?

Those are different questions. They require different tools.

One client’s story

A client came to me having spent over £5,000 on supplements over three years. Her GP had run standard bloods twice, and she’d been told her thyroid, iron and cholesterol were fine.

We found H. pylori she didn’t know she had. Her ferritin was 14 µg/L (14 ng/mL): inside her lab’s range, but below 15 µg/L (15 ng/mL), where iron stores are absent (BSG 2021). H. pylori is linked to iron deficiency, and treating it helps iron stores recover (Wang 2025, a review of studies in children). Her daytime cortisol pattern was flat, which I treated as a clue to follow up, not a diagnosis. Her IgG panel reacted to gluten and dairy, which we used to choose a trial elimination, not as proof of an allergy.

We worked through them in order, and within four months her energy had come back. That’s one person’s story, not evidence it would work for everyone. What it shows is that the £5,000 hadn’t been aimed at anything.

What testing looks like here

The TDG programme runs five tests together: blood chemistry (57 to 87 markers, depending on the panel), GI-MAP stool testing, DUTCH Plus hormones, Metabolomix+ (organic acids, amino acids and oxidative-stress markers from a first-morning urine sample) and an IgG food panel (286 foods).

Read together, they explain each other. A low ferritin means something different when the stool test shows H. pylori. A borderline B12 on the blood test means more when methylmalonic acid is raised on the urine test. That cross-checking is the point: one result is a clue, several that agree are a case.

The questions to ask your GP

If you’ve been told your results are normal and you still feel unwell, it’s worth asking:

• What was the actual number, not just “normal”?
• Has fasting insulin been tested, or only glucose?
• Has Free T3 been checked alongside TSH?
• For ferritin: what’s the actual number, and was CRP checked at the same time? Ferritin rises with inflammation, so WHO advises measuring it alongside inflammation markers, and uses a higher cut-off, below 70 µg/L (70 ng/mL), in adults with infection or inflammation (WHO 2020). In active inflammatory bowel disease, the BSG notes that up to 100 µg/L (100 ng/mL) can still mean iron deficiency (BSG 2021).

Some GPs will help with these. Some systems aren’t set up to. Either way, knowing the number is the start.

The bottom line

“Your tests are normal” means your results sit inside a range built to catch disease. It doesn’t mean nothing is worth looking at, and it doesn’t mean you should feel the way you do.

In nearly forty years of working with people, most of the time a fuller set of tests finds something worth acting on. Sometimes it finds nothing, and that’s useful too: it tells us where not to spend your money.

References

1. American Society of Hematology (Powers JM et al.). American Society of Hematology 2026 guidelines for diagnosis of iron deficiency. Blood Adv 2026. PMID 42747316. doi:10.1182/bloodadvances.2025015950. Thresholds as reported in published summaries of the guideline; the abstract doesn’t list them.
2. Demay MB et al. Vitamin D for the prevention of disease: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab 2024;109:1907–47. PMID 38828931. doi:10.1210/clinem/dgae290
3. Garcia-Casal MN et al. Serum or plasma ferritin concentration as an index of iron deficiency and overload. Cochrane Database Syst Rev 2021;5:CD011817. PMID 34028001. doi:10.1002/14651858.CD011817.pub2. In adults seeing a doctor, ferritin below 30 µg/L: sensitivity 79%, specificity 98% (low-certainty evidence).
4. Martí-Carvajal AJ et al. Homocysteine-lowering interventions for preventing cardiovascular events. Cochrane Database Syst Rev 2017;8:CD006612. PMID 28816346. doi:10.1002/14651858.CD006612.pub5
5. Mast AE et al. Clinical utility of the soluble transferrin receptor and comparison with serum ferritin in several populations. Clin Chem 1998;44:45–51. PMID 9550557 (no DOI indexed). Tested in 62 anaemic patients; cut-off 30 µg/L or below.
6. Mei Z et al. Comparison of current World Health Organization guidelines with physiologically based serum ferritin thresholds for iron deficiency in healthy young children and nonpregnant women using data from the Third National Health and Nutrition Examination Survey. J Nutr 2023;153:771–80. PMID 36803577. doi:10.1016/j.tjnut.2023.01.035. Reports WHO’s thresholds (below 12 µg/L in young children, below 15 µg/L in women) and argues they are set too low.
7. Snook J et al. British Society of Gastroenterology guidelines for the management of iron deficiency anaemia in adults. Gut 2021;70(11):2030–51. PMID 34497146. doi:10.1136/gutjnl-2021-325210. Below 15 µg/L: absent iron stores; below 30 µg/L: low iron stores; up to 100 µg/L can still mean iron deficiency in active inflammatory bowel disease.
8. Tabák AG et al. Trajectories of glycaemia, insulin sensitivity, and insulin secretion before diagnosis of type 2 diabetes. Lancet 2009;373:2215–21. PMID 19515410. doi:10.1016/S0140-6736(09)60619-X
9. Verdon F et al. Iron supplementation for unexplained fatigue in non-anaemic women: double blind randomised placebo controlled trial. BMJ 2003;326:1124. PMID 12763985. doi:10.1136/bmj.326.7399.1124
10. Wang Z et al. Impact of Helicobacter pylori infection on iron deficiency anemia in children: a systematic review and meta-analysis with early intervention implications. Front Microbiol 2025;16:1541011. PMID 40611956. doi:10.3389/fmicb.2025.1541011
11. World Health Organization. WHO guideline on use of ferritin concentrations to assess iron status in individuals and populations. Geneva: WHO; 2020. ISBN 9789240000124. NBK569877