Inherited
Most common in people of Celtic and northern European descent. A result carries information for close relatives as well as the individual tested.
Genetics guide
Hereditary haemochromatosis.
One of the most common inherited conditions in northern European populations — and one of the most commonly missed. Here is what the genetics mean, and how to turn a result into a useful conversation with your doctor.
1 in 3
of people with Celtic or northern European ancestry carry at least one copy of an HFE variant
4%
of FitnessGenes customers carry two copies of the higher-risk group variants
2
blood tests establish whether iron is actually accumulating
Introduction
A common condition, described long before it was understood.
People across Ireland, Scotland and Wales identified an illness pattern centuries ago, long before its cause was understood. The condition is now formally called hereditary haemochromatosis, an inherited disorder where the body absorbs and retains more iron than necessary. While iron is vital and normally carefully controlled, excess iron can cause silent damage.
What makes it more problematic is not the severity but the ordinariness. The early complaints are fatigue, poor concentration and joint pain — three of the most common presentations in general practice, and three of the hardest to attribute. So the condition is both one of the most prevalent inherited disorders and one of the most frequently missed diagnoses.
Gradual
Iron accumulates over years or decades, usually without symptoms. Timing varies widely between people who carry the genetic variants.
Actionable
Two blood tests detect it, and the established treatment is the removal of blood at intervals. Identified early, serious consequences are largely preventable.
Why genetic testing matters
Many people feel fatigued. Standard dietary advice often focuses on preventing iron deficiency by recommending increased red meat intake, supplements if necessary, and pairing iron with vitamin C to enhance absorption. This guidance is generally appropriate for most people — but for individuals prone to iron overload, following it can be the exact opposite of what they need.
Understanding your genetics early provides significant practical benefit. While sometimes it can diagnose conditions directly, it more often helps you identify the right health advice to follow, which blood tests to request, and which general advice might not apply to you.
Ancestry and risk
A Celtic inheritance, carried around the world.
The risk variants behind hereditary haemochromatosis reach their highest frequencies in the formerly Celtic-speaking populations of Ireland, Scotland and Wales. Ancient DNA places the principal variant there at least 4,000 years ago. But those populations did not stay put: the great emigrations of the nineteenth and twentieth centuries carried that genetic legacy to North America, Australia and New Zealand — where it persists today, largely unrecognised.
Close to five million Irish people emigrated to the United States, alongside comparable Scottish movement to Canada, Australia and New Zealand. They left in family and community groups and frequently married within them for generations after arrival, which preserved the elevated variant frequency rather than diluting it.
Clinical awareness tracks the visibility of the condition rather than its prevalence. In Ireland and the UK it is a recognised differential for unexplained fatigue and joint pain; elsewhere it is often not considered at all, so the same genetics produce far later diagnosis.
People reporting Irish or Scottish ancestry, by region
US Northeast~32M
Atlantic Canada & Ontario~9M
Australia & New Zealand~9M
Appalachia & upland South~8M
Chicago & Great Lakes~4M
Where Irish, Scottish, Welsh or northern English ancestry is present in a family, awareness of this risk is warranted regardless of current country of residence.
Why iron accumulates
A regulator that does not switch off.
Iron absorption is normally tightly controlled. The hormone hepcidin suppresses iron uptake from the gut once your stores are adequate. In haemochromatosis, hepcidin activity is deficient, so you continue to absorb iron from food while white blood cells in the spleen release more into the bloodstream. Circulating and stored iron levels rise year on year — silently, often for decades.
01
Excess absorption
With hepcidin activity deficient, more dietary iron enters the body than it needs, and there is no signal to stop. Iron-rich foods, supplements and vitamin C all increase absorption.
02
Transport saturates
Transferrin, the protein that carries iron in the blood, becomes saturated. This is the earliest measurable sign — transferrin saturation rises before stores are substantially elevated.
03
Stores build
Ferritin rises as iron is deposited in the liver, heart, pancreas and joints. The burden is cumulative, so it reflects years of absorption rather than the current week.
04
Tissue damage
Deposited iron generates reactive oxygen species, injuring cells. If untreated, this leads to fibrosis and organ dysfunction — hepatic cirrhosis, cardiac disease, diabetes and arthropathy.
At stages 2 or 3, iron overload is manageable, and the organ damage of stage 4 is largely preventable.
What it feels like
Symptoms can resemble many conditions.
Since iron builds up gradually, early symptoms tend to be non-specific. Fatigue, difficulty concentrating and joint pain are common complaints in general practice, but they are often difficult to link to a single cause — which is exactly what makes this condition both prevalent and frequently missed.
Persistent fatigue
Tiredness that rest does not resolve — usually the first thing people notice, and the easiest to explain away.
Brain fog
Impaired concentration and slower recall, often described as thinking through fog.
Joint pain
Frequently the hands, and often the second and third knuckles. Can appear well before other signs.
Abdominal discomfort
Vague pain or fullness in the upper right abdomen as iron is deposited in the liver.
Hormonal changes
Reduced libido, and in some cases changes to menstrual or erectile function, as the pituitary is affected.
Bronzed complexion
A darkening or grey-bronze cast to the skin in longer-standing overload.
In men
Symptoms typically emerge between 30 and 50. With no regular route of iron loss, stores build steadily from early adulthood, so men present earlier and more often. Fatigue and joint pain are usually the first complaints, and alcohol intake accelerates both accumulation and liver risk.
In women
Onset usually occurs later, typically after menopause, since menstruation depletes iron during reproductive years. Pregnancy and breastfeeding also help protect iron levels. After this loss ceases, iron can build up quickly, making post-menopausal testing important even if previous results were normal.
Why you should not wait for symptoms: iron can accumulate for years before producing any detectable clinical sign. By the time symptoms are unmistakable, damage may already be established — so testing beats waiting.
The HFE variants
Two variants, and the copies you carry.
Type 1 haemochromatosis — the predominant form in European populations — arises from variants in a single gene, HFE, which controls the levels of hepcidin. Inheritance is autosomal recessive: two copies are needed for the higher-risk picture, while a single copy makes you a carrier. C282Y is the principal contributor; H63D is milder, associated with smaller elevations in iron stores.
| Genotype | C282Y | H63D | What it means |
|---|---|---|---|
| Non-carrier | 0 | 0 | No elevated risk attributable to these two variants. |
| Carrier (C282Y) | 1 | 0 | Accumulation is unusual. A 50% chance of passing the variant to each child. |
| Compound heterozygote | 1 | 1 | Modestly raised likelihood, typically mild. About 5% of diagnosed European cases. |
| C282Y homozygote | 2 | 0 | The highest-risk genotype: 80–95% of diagnosed European cases; 1 in 200 among northern Europeans. |
- Two copies of C282Y do not constitute a diagnosis of haemochromatosis; they identify membership of the group in which the condition is most likely to develop.
- A substantial proportion of C282Y homozygotes never accumulate clinically significant quantities of iron.
- Sex, age, alcohol consumption, blood loss, diet and additional genetic factors all modify the expression of that risk.
Biochemical assessment
The two tests to ask for.
Genetic analysis establishes predisposition; biochemical testing establishes whether iron is in fact accumulating. These two measures detect overload directly.
Earliest signal
Transferrin saturation
The share of your iron-transport capacity that is currently occupied. It rises before stores do.
Usual range~20–45%
Worth investigatingPersistently above 45%; above 50% in men and 45% in women
Total burden
Serum ferritin
How much iron is held in storage — the cumulative load, and the number used to track treatment.
Usual range~30–300 µg/L men, 15–200 µg/L women
Worth investigatingAbove your sex-specific limit; above 1,000 µg/L usually prompts specialist review
Suggested wording for your doctor: "I have a genetic predisposition to hereditary haemochromatosis. Could I have a transferrin saturation and a serum ferritin measured, together with liver function tests, and could the numerical values be provided rather than an indication of 'normal'?"
Get the full guide.
- The full genetics and ancestry breakdown
- A tear-out card of exactly what to ask your doctor
- Referenced against 11 clinical studies and guidelines
A free, evidence-graded PDF briefing on hereditary haemochromatosis — the genetics, the ancestry risk, and exactly what to ask your doctor for.
Download the free guideThis guide is provided for information and does not constitute medical advice, diagnosis or treatment. Reference ranges and diagnostic thresholds vary between laboratories and guidelines; all results should be interpreted by the clinician who ordered them.