Getting tested for celiac

If someone in your family has celiac, you are the person most likely to have it

Celiac runs in families. A parent, brother, sister or child of someone diagnosed has roughly a one in ten chance, against about one in a hundred in the general population.

Guidance already says those relatives should be tested. In practice most never are — which means the people most likely to be walking around undiagnosed are the relatives of people who already know.

What to ask for

The first-line blood test is tTG-IgA. Ask for total IgA at the same time — some people do not make much IgA, and without that second number a negative tTG can be meaningless.

Asking for the test by name gets further than describing symptoms. You are not asking for a diagnosis, you are asking for a screen.

If the test is negative and you are still ill

A negative tTG is not always the end of it. A small share of people with celiac do not test positive on the standard screen, and one family told us their daughter's tTG came back negative every time — her IgA was low enough to skew the result but not low enough to trigger the backup test. It took a different antibody test to find it.

When it is not the gut that is damaged

Celiac does not always show up as a stomach problem. It can present neurologically — unsteadiness and coordination problems, numbness or tingling in the hands and feet, persistent headaches, brain fog. These are recognised presentations, not fringe ones.

This matters for testing, because the standard screen is looking in the wrong place. A tTG-IgA is testing for the autoimmune response in your intestine. If the damage is happening in your cerebellum instead, that test can come back normal while something is very much wrong — and once it comes back normal, most people stop looking.

One reader told us she waited seven years for a referral to the only service in her country that tests for gluten ataxia, having worked it out herself after five. Another told us it took forty-one years.

Two things worth knowing. You can have celiac and a gluten-related neurological condition — they are not alternatives. And where nerve or cerebellar damage has been going on for years, it does not always fully recover once gluten is out, which is the reason not to leave it.

This is a specialist area and the testing is not routine, so a GP may not have come across it. Both the Celiac Disease Foundation and Coeliac UK cover the neurological side — search either for “neurological” and take what you find with you.

The genetic test, and what it is actually for

Celiac requires one of two genes, HLA-DQ2 or HLA-DQ8. Almost everyone with celiac carries one.

A negative result is the useful one. Almost everyone with celiac carries one of these genes, so a negative result makes it extremely unlikely and is generally taken as ruling it out. Your doctor can say whether any further testing is worth doing in your case.

A positive result means very little on its own. Roughly a third of people carry these genes and most never develop celiac. It means the blood test is still worth doing, not that you have anything.

Two situations where it is the right test: someone who has already gone gluten free and cannot face eating it again, and a child who would otherwise be re-screened every few years for the rest of their childhood.

A 23andMe or Ancestry result is not the same as clinical HLA-DQ typing. Do not rule celiac in or out on a consumer DNA kit.

If you are told to wait for symptoms

People are told this, including about their own children. The problem is that celiac does not require symptoms to do damage.

One family had their daughter diagnosed, tested their other two children, and found a second case with no symptoms at all. She would never have been found by waiting. It is the version that turns up years later as anemia or bone density loss in someone who always said they felt fine.

If the answer is about cost or resources, the genetic test is worth raising specifically: it is done once rather than repeated, and it either makes celiac extremely unlikely or tells you he is worth keeping an eye on.

What waiting actually costs

Celiac is not a stomach ache you put up with. While it is undiagnosed the gut is not absorbing properly, and the damage is mostly quiet and cumulative rather than dramatic.

• Iron deficiency and anemia — often the first sign, and frequently treated for years as its own problem without anyone asking why.
• Thinning bones. Calcium and vitamin D are among the first things to stop being absorbed, and bone density lost over a decade does not fully come back.
• In children, growth. Poor weight gain, falling off the growth curve, late puberty, damage to tooth enamel. Time-limited in a way the others are not — a child only grows once.
• Fatigue that gets explained away. Years of being told it is stress, or work, or getting older.
• Fertility problems and recurrent miscarriage, which are associated with undiagnosed celiac and are often the thing that finally prompts testing.
• Other autoimmune conditions — once you have one the odds of a second rise, and thyroid disease alongside celiac is common enough that families here mention it constantly.

There are rarer and more serious outcomes at the far end of a long undiagnosed stretch. They are genuinely rare and not the reason to get tested — the anemia, the bones and the years are reason enough.

Nearly all of it stops when you stop eating gluten. The gut heals, the bloods come back, energy returns, children catch up. That is what the test buys: not bad news, but the point at which the damage stops.

Who to send this to

Your parents. Your brothers and sisters. Your children. They are the one in ten.

And anyone who has been unwell for years with nothing to show for it. Almost every diagnosed adult we have spoken to got there by pushing, not by being offered.