Familial hyper­cholesterolemia: signs, testing and what to do

Familial hypercholesterolemia (FH) is an inherited condition that keeps LDL cholesterol high from birth. It affects about 1 in 250 people, and most of them don't know they have it. Doctors suspect it when an adult's LDL is above about 4.9 mmol/L (190 mg/dL) or total cholesterol is above 7.5 mmol/L (290 mg/dL), especially when a close relative had heart disease young. Treatment almost always means medicine as well as a healthy diet.

What FH is

Your liver clears LDL cholesterol from your blood using LDL receptors on the surface of its cells. In FH, a change in one gene means this doesn't work properly, so LDL builds up in the blood from childhood, however healthily you eat. HEART UK explains that most people with FH have a change in an LDL receptor (LDLR) gene. Only 2 or 3 in every 100 have a change in the APOB gene, and a few have one in PCSK9.

Most people inherit one altered gene, from one parent. This is heterozygous FH, and it's the type this guide is about. Inheriting an altered gene from both parents causes homozygous FH, which is very rare and much more severe: NICE considers it when an adult's LDL is above 13 mmol/L (about 500 mg/dL). It's managed in specialist centres.

The Family Heart Foundation estimates that FH affects about 1 in 250 people worldwide, and that only around 30% of them know they have it. Because LDL is high from birth, the damage to arteries builds up over many years. That's why untreated FH can cause heart attacks in people in their 30s, 40s and 50s.

Signs and symptoms

High cholesterol, FH included, usually causes no symptoms. The NHS says the only way to find out is a blood test. FH is most often picked up in one of these ways:

• A very high cholesterol result, often found at a routine check.
• A family history of high cholesterol, or of heart attacks and heart disease at a young age.
• Physical signs, which are easy to miss and not everyone has:
  • Tendon xanthomas: thickened tendons or small fatty lumps on the knuckles or the Achilles tendon at the back of the ankle.
  • Xanthelasma: raised, pale yellow patches on or around the eyelids.
  • Corneal arcus: a white or grey ring around the coloured part of the eye.

NICE stresses that not having these signs doesn't rule FH out. Plenty of people with FH never develop them.

The criteria doctors use, in plain English

Before diagnosing FH, doctors first rule out other causes of high cholesterol, such as uncontrolled diabetes, an underactive thyroid, liver or kidney disease, heavy drinking and some medicines. NICE also asks for two LDL measurements, because results vary from test to test.

Simon Broome criteria (used across the UK)

The first step is a cholesterol level above these thresholds, measured before treatment or the highest level on treatment:

Then, as HEART UK sets out:

• Definite FH is those levels plus either tendon xanthomas (in you, a parent, brother, sister or child, or a grandparent, uncle or aunt) or a DNA test showing an FH gene change.
• Possible FH is those levels plus at least one of:
  • A heart attack in a parent, sibling or child before 60, or in a grandparent, uncle or aunt before 50.
  • Total cholesterol above 7.5 mmol/L in an adult parent, sibling, child, grandparent, uncle or aunt, or above 6.7 mmol/L in a child or sibling under 16.

Dutch Lipid Clinic Network (DLCN) score

The Dutch criteria give points for your LDL level, physical signs, your own heart history and your family's. Add them up:

• More than 8 points: definite FH
• 6 to 8: probable FH
• 3 to 5: possible FH

NICE's FH guideline (CG71) says to refer someone to an FH specialist service for a DNA test if they meet the Simon Broome criteria for possible or definite FH, or score more than 5 on the Dutch criteria. Wales uses its own version of the Dutch score.

Other red flags

• NICE suspects FH in any adult with total cholesterol above 7.5 mmol/L (290 mg/dL), or with a personal or family history of heart disease before 60 in the person or a parent, sibling or child.
• NICE's main heart-risk guideline (NG238) says anyone with total cholesterol above 9.0 mmol/L (348 mg/dL) or non-HDL above 7.5 mmol/L (290 mg/dL) should be seen by a specialist, even without a family history.
• In the US, the Family Heart Foundation says FH is suspected when untreated LDL is above 190 mg/dL (4.9 mmol/L) in adults or above 160 mg/dL (4.1 mmol/L) in children, especially with early heart disease in the family (before 55 in men, before 65 in women).

Not sure what your numbers mean? Our guide to reading cholesterol results covers every line of a lipid panel, and the unit converter switches between mmol/L and mg/dL.

Why diet alone isn't enough

This is the hardest part of an FH diagnosis for many people, especially those who already eat well. FH isn't caused by diet: the problem is how your liver clears LDL. Diet can still lower LDL, but only by a fraction of what's needed.

Here's a worked example. Take an adult with FH and an untreated LDL of 5.5 mmol/L (213 mg/dL):

• The Portfolio Diet, one of the most effective eating patterns for LDL, lowered it by about 13 to 17% in trials. That would bring this person to about 4.6 to 4.8 mmol/L (177 to 185 mg/dL), still above the FH threshold.
• NICE recommends a high-intensity statin for every adult with FH, aiming for at least a 50% fall in LDL from the starting level. For this person, that means getting to about 2.75 mmol/L (106 mg/dL) or lower.

NICE's guideline is direct about it: lifestyle advice is "a component of medical management, and not as a substitute" for medicine. The Family Heart Foundation says the same: diet and exercise matter, but for people with FH they're not enough.

Diet still counts, though. It adds to what medicine does, and it lowers the other risks that build up alongside FH. NICE's advice for people with FH is:

• Total fat at 30% or less of calories, and saturated fat at 10% or less, swapping it for unsaturated fats such as olive and rapeseed oil, nuts and seeds.
• Dietary cholesterol under 300 mg a day.
• At least 5 portions of fruit and vegetables a day, and at least 2 portions of fish a week (1 of them oily).
• If you use foods with added plant sterols or stanols, take them every day: they only work if taken consistently.
• No routine omega-3 supplements.
• Regular physical activity, a healthy weight, and not smoking.

Our low-cholesterol recipes and food swaps are a practical place to start.

How FH is treated

Treatment is set by your doctor or lipid clinic, but it helps to know what to expect:

• Adults: NICE recommends starting a high-intensity statin (atorvastatin 20 to 80 mg or rosuvastatin 10 to 40 mg) and increasing the dose if needed to reach a fall of more than 50% in LDL. If that isn't enough, ezetimibe can be added, and people at very high risk or still not at goal may be offered injectable treatments through a specialist.
• The US 2026 guideline has its own section for people with LDL of 190 mg/dL (4.9 mmol/L) or more. It sets an LDL goal of below 100 mg/dL (2.6 mmol/L) on treatment, and below 55 mg/dL (1.4 mmol/L) for those who already have heart or artery disease.
• Children: NICE says children with FH should be offered a statin by the age of 10, started by a specialist in a child-focused setting.
• Pregnancy: statins aren't used in pregnancy. NICE advises stopping them 3 months before trying to conceive, so if you're planning a pregnancy, discuss it with your doctor first.
• Reviews: NICE recommends a structured review at least once a year, with a lipid profile to check progress.

After starting or changing treatment, LDL usually falls within weeks. See how long it takes to lower cholesterol for when re-tests are usually done.

Family (cascade) testing

The Family Heart Foundation sums it up: "you never find a person with FH, you find a family." Once one person has a confirmed gene change, cascade testing traces it through the family:

• NICE recommends DNA testing of first-degree relatives (parents, brothers, sisters, children), second-degree relatives (grandparents, aunts, uncles, nieces, nephews, half-siblings) and, where possible, third-degree relatives such as first cousins.
• Children aged up to 10 with one affected parent should be offered a DNA test as early as possible, with another chance by age 10 if it was missed.
• If DNA testing shows that a relative hasn't inherited the gene change, their heart risk is managed like anyone else's.
• NICE asks FH specialists to help you share the news with relatives and to track who has been tested at each annual review.

FH is also one of the groups HEART UK says should have Lp(a) measured: a second inherited cholesterol particle that adds to heart risk.

How to get tested

In the UK (NHS)

• Start with your GP. Ask for a full lipid profile if you haven't had one, and tell them about any relatives with very high cholesterol or early heart disease, including how old they were.
• Ask whether you meet the Simon Broome or Dutch criteria. If you do, NICE says you should be referred to an FH specialist service or lipid clinic for a DNA test.
• Draw up your family tree. The specialist will want at least three generations: who had high cholesterol or heart disease, at what age, and whether they smoked.
• GP practices are also asked to search their records for people under 30 with total cholesterol above 7.5 mmol/L, and people 30 or older above 9.0 mmol/L, so you may be contacted first.
• HEART UK has a lipid clinic finder and FH information.

In the US

• Get a lipid panel. The 2026 ACC/AHA guideline recommends one from age 19 at least every 5 years, and a one-off check in children aged 9 to 11, which is when many FH cases come to light.
• Raise FH directly if your untreated LDL is 190 mg/dL or more, or if a parent or sibling had heart disease young.
• Ask about genetic testing. A cardiologist, lipid specialist or genetic counselor can arrange it. The Family Heart Foundation notes that a negative test doesn't rule FH out, and suggests discussing privacy questions before testing.
• The Family Heart Foundation has a Find a Specialist directory and Care Navigators who can help you find a clinic.

Questions to take to your appointment

• Do my cholesterol results and family history meet the criteria for FH?
• Can I be referred for a DNA test, or to a lipid clinic?
• What LDL level are we aiming for, and how will we know treatment is working?
• Should my children, parents and siblings be tested, and how do I tell them?
• Should I have my Lp(a) measured?

Sources

• NICE CG71: Familial hypercholesterolaemia: identification and management (last updated October 2019). Recommendations 1.1, 1.2, 1.3 and 1.5.
• NICE NG238: Cardiovascular disease: risk assessment and reduction, including lipid modification. Recommendation 1.4.5.
• HEART UK: What are the diagnostic criteria for FH?, What is FH? and Diagnosing FH.
• Family Heart Foundation: Familial hypercholesterolemia, Diagnosing FH and Genetic testing and FH.
• Blumenthal RS, Morris PB, et al. 2026 ACC/AHA Guideline on the Management of Dyslipidemia. J Am Coll Cardiol. 2026;87(19). Sections 3.1 and 4.2.4.
• NHS: High cholesterol (reviewed March 2026).
• Jenkins DJA, et al. Effect of a dietary portfolio of cholesterol-lowering foods given at 2 levels of intensity of dietary advice. JAMA. 2011;306:831–839; Chiavaroli L, et al. Prog Cardiovasc Dis. 2018;61:43–53.

Frequently asked questions

What is familial hypercholesterolemia?

Familial hypercholesterolemia (FH) is an inherited condition in which a gene change stops the liver clearing LDL cholesterol from the blood properly, so LDL is high from birth. It affects about 1 in 250 people. Without treatment it can cause heart disease at a young age, but it can be treated with medicine and a healthy lifestyle.

What are the signs of familial hypercholesterolemia?

Usually there are none, which is why FH is mostly found through a cholesterol test and family history. Some people develop thickened tendons or fatty lumps on the knuckles or Achilles tendons, yellow patches around the eyes, or a pale ring around the iris. NICE says not having these signs doesn't rule FH out.

What cholesterol level suggests FH?

Under the Simon Broome criteria used in the UK, FH is considered in adults with total cholesterol above 7.5 mmol/L (290 mg/dL) or LDL above 4.9 mmol/L (190 mg/dL), and in children under 16 with total cholesterol above 6.7 mmol/L or LDL above 4.0 mmol/L, together with a family history or physical signs. In the US, FH is suspected at an untreated LDL above 190 mg/dL in adults or 160 mg/dL in children.

Can you treat familial hypercholesterolemia with diet alone?

No. Diet lowers LDL by a fraction of what's needed in FH. Even the most effective cholesterol-lowering diets cut LDL by roughly 13 to 17% in trials, while NICE aims for at least a 50% reduction with a high-intensity statin. Diet still matters alongside medicine, but NICE says it isn't a substitute for it.

Should my children be tested for FH?

Yes, if you have FH. Each child has a 1 in 2 chance of inheriting it. NICE recommends offering a DNA test to children of an affected parent as early as possible, and by age 10 at the latest, and offering children with FH a statin by about age 10.

Can I get a genetic test for FH on the NHS?

Yes, through referral. If your GP finds you meet the Simon Broome criteria for possible or definite FH, or score more than 5 on the Dutch Lipid Clinic Network criteria, NICE says you should be referred to an FH specialist service for a DNA test. Once your gene change is known, relatives can be offered cascade testing.

Does high cholesterol cause symptoms?

Usually not. The NHS says high cholesterol doesn't usually cause symptoms and you can only find out from a blood test. In FH, very high levels over many years can cause visible cholesterol deposits on tendons or around the eyes, but many people with FH never have them.

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