Your Guide to Hereditary Angioedema: Symptoms, Treatments, and More

Hereditary Agioedema Diagnosis: Tests and What To Expect

Medically reviewed by Deborah Pedersen, M.D.

Written by Emily Wagner, M.S.

Posted on July 13, 2026

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Key Takeaways

Hereditary angioedema, or HAE, is a rare condition that causes swelling attacks and is often confused with allergies or stomach problems, leading many people to wait seven to 10 years before getting the right diagnosis.

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Have you ever wondered whether your swelling attacks could be hereditary angioedema (HAE)? This rare condition is often mistaken for allergies, stomach problems, or other health conditions. Because of this, many people wait seven to 10 years after their symptoms begin before getting the right diagnosis.

This article explains why an HAE diagnosis is often delayed, which tests can help confirm it, and what to expect during the diagnosis process.

Why Is HAE Usually Misdiagnosed?

Hereditary angioedema looks like many other health conditions, which makes it hard to diagnose. Because it’s also very rare, many doctors mistake HAE for more common problems.

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A delayed diagnosis can affect your quality of life. People with HAE who are misdiagnosed may spend more on treatment or undergo unnecessary medical procedures.

Common HAE symptoms include:

Abdominal pain
Angioedema (swelling), often in the arms, legs, and face
Trouble breathing or swallowing due to swelling in the throat
A nonitchy rash (not hives)

HAE may be mistaken for other conditions, such as intestinal blockages or allergic reactions to foods or drugs.

Symptoms usually occur as sudden swelling attacks, with periods of few or no symptoms in between. For some people, stress or another trigger, such as an injury, surgery, or anxiety, can bring on an attack.

It may help to track what you were doing before an attack started. Keeping a journal of your HAE attacks and symptoms can help your doctor make the right diagnosis sooner.

What Blood Tests Help Diagnose HAE?

Blood tests can help diagnose hereditary angioedema and show which of the three types you have. Doctors usually check the levels and function of several proteins, including C1 inhibitor (C1INH).

Type 1 HAE — The body doesn’t make enough C1INH. This can lead to inflammation and swelling attacks, also called angioedema.
Type 2 HAE — The body makes C1INH, but the protein doesn’t work the way it should. Swelling attacks can still happen.
HAE with normal C1INH — In rare cases, C1INH levels and function are normal. Doctors may look for other causes, including certain gene changes, that can lead to swelling attacks.

C4 Levels

C4 is one of more than 50 proteins in the complement system, which helps your immune system fight infections. When checking for HAE, doctors often start with a C4 blood test because it’s widely available and relatively inexpensive.

During an HAE attack, C4 levels usually drop. People with type 1 HAE often have low C4 levels even between attacks. If you have low C4 levels, your doctor will likely order additional blood tests to help confirm an HAE diagnosis.

C1 Inhibitor Testing

C1INH is another protein in the complement system. Measuring the amount of C1INH in your blood helps doctors diagnose HAE. People with type 1 HAE usually have low C1INH levels.

Blood tests can also measure how well C1INH works. People with type 2 HAE usually have normal or near-normal C1INH levels, but the protein doesn’t function like it should.

C1q Level Testing

Measuring levels of another complement protein, called C1q, can help doctors tell hereditary angioedema from acquired angioedema.

Acquired angioedema develops later in life and isn’t inherited. It can happen when the immune system makes proteins called autoantibodies that attack C1INH.

People with acquired angioedema often have low C1q levels. People with HAE typically have normal C1q levels.

Determining HAE Type

Doctors use your blood test results, symptoms, and family history to help diagnose the type of HAE you may have:

Type 1 HAE — Low C4, low C1INH levels, and low C1INH function
Type 2 HAE — Low C4 levels, normal C1INH levels, and low C1INH function

Your doctor may repeat these blood tests one to three months later to confirm the diagnosis. This is because infections and other illnesses can also affect complement protein levels.

HAE with normal C1INH is more difficult to diagnose. People with this type have normal C1INH levels and normal C1INH function. Doctors may order genetic testing to look for gene changes linked to this form of HAE.

When Is Genetic Testing Needed for HAE?

Genetic testing in HAE isn’t always necessary. In most cases, blood tests that measure complement proteins are enough to diagnose HAE.

Genetic testing also can’t predict how HAE will progress over time. It can only identify a genetic change linked to the disease.

Genetic Testing for HAE

If blood tests suggest HAE, your doctor may recommend genetic testing. These tests look for changes in genes linked to different forms of HAE.

For people with type 1 or type 2 HAE, doctors may look for changes in the SERPING1 gene. This gene provides instructions for making the C1INH protein. Changes in SERPING1 can cause the body to make too little C1INH or to make C1INH that doesn’t work properly.

If blood tests suggest HAE with normal C1INH, doctors may look for changes in other genes, including:

F12 — Provides instructions for making coagulation factor XII (12), a protein involved in blood clotting and inflammation
ANGPT1 — Provides instructions for making a protein that helps keep blood vessels healthy
KNG1 — Provides instructions for making a protein that works with factor XII and plays a role in inflammation
PLG — Provides instructions for making plasminogen, a protein involved in breaking down blood clots

How Does Family Screening for HAE Work?

If you’ve been diagnosed with HAE, your doctor may advise that your close family members also be tested. Parents, siblings, and children of someone with HAE should be screened because they have a higher chance of having the condition.

Hereditary conditions like HAE are passed down from parents to their children. Everyone inherits one copy of each gene from each parent.

For example, a child inherits one copy of the SERPING1 gene from each parent. If one copy has a disease-causing mutation (change), the child may develop HAE.

HAE is inherited in an autosomal dominant pattern. This means a child needs to inherit only one altered copy of the SERPING1 gene to develop HAE. If one parent has HAE, each child has a 50/50 chance of inheriting the condition.

Not everyone with HAE has a family history of the disease. Studies show that up to 1 in 4 HAE cases are caused by a de novo (new) mutation that occurs for the first time in that person.

What To Expect After Family Screening

Family screening can help identify relatives who also have HAE. If you’re planning to have children and you have HAE, a genetic counselor can help you understand your family’s risk and discuss your options. Genetic counselors are professionals trained to explain genetic conditions and testing, including what the results may mean for the person diagnosed and their family.

Learning about a genetic condition can be stressful. A genetic counselor can answer your questions and help you understand what to expect after an HAE diagnosis.

When Should I Get HAE Testing?

If you think you may have HAE, talk with your doctor about your symptoms. Signs that you should be tested for HAE include:

Repeated angioedema (swelling) without hives
Swelling that doesn’t improve with allergy medications, such as antihistamines, corticosteroids, or epinephrine
Severe stomach or abdominal pain
Swelling in your throat or upper airway that makes it hard to breathe
Symptoms or attacks that happen after stress, illness, injury, or surgery

A family history of hereditary angioedema or similar swelling attacks can also point to HAE. Many people with HAE first notice symptoms during childhood or their teenage years.