Why do I feel sick after eating?

We've all overeaten once or twice and made ourselves feel ill. However, if you regularly feel sick after eating, the cause may be an underlying health issue.

Digestive nausea is linked to a variety of different conditions. In this article, we’ll look at some medical complaints which cause nausea after eating. We’ll explain the various symptoms associated with nausea after eating and advise you when it’s time to see a doctor.

What causes nausea after eating?

A wide variety of medical conditions or complaints can cause feelings of nausea after eating. These are a few of the most common:¹

Allergic reactions or food intolerance

Many people have allergies or are intolerant to commonly eaten foods, including lactose products (e.g. milk and dairy), shellfish, gluten products (e.g. bread and pasta), or high FODMAP foods (foods rich in short-grain carbohydrates).²

Nausea is one symptom of food allergy or intolerance. Still, it is often accompanied by other symptoms, which can be as mild as uncomfortable gas, and as severe as hives, swelling, and anaphylactic shock.

Gastrointestinal problems

Nausea after eating may be caused by these common digestive complaints:

• GERD (gastroesophageal disease). GERD is caused by stomach acid entering the oesophagus and is the leading cause of heartburn.³
• gallbladder diseases. When the gallbladder is diseased, the body can’t process fat correctly, and people then experience nausea after eating high-fat food.
• IBS. Irritable bowel syndrome typically causes bloating and gas in individuals after they eat certain trigger foods. Sometimes this can cause nausea while digesting.⁴

Pregnancy

Morning sickness is often one of the first indicators of pregnancy. However, ‘morning’ sickness can occur throughout the day and is frequently exacerbated after eating.⁵

Most women only experience feelings of sickness during the first trimester, unless they are suffering from hyperemesis gravidarum, which causes severe nausea and illness throughout the pregnancy.

Chemotherapy treatments 

Patients undergoing cancer treatment often report increased food intolerance or nausea after eating, which is a common side effect of chemotherapy.⁶

Migraines

Severe migraines often coincide with digestive nausea, which medical professionals believe is because the gut and the brain communicate with each other.⁷ The so-called ‘gut-brain axis’ gives you stomach butterflies when you’re excited, and also makes you sick when you have a migraine.

Different symptoms of nausea after eating

Different medical complaints cause various symptoms in addition to nausea:

• food allergies or intolerances can cause swelling, hives, skin discomfort, shortness of breath, and diarrhoea
• gastrointestinal problems can cause gas, bloating, diarrhoea, and constipation
• pregnancy can cause breast soreness, missed periods, and tiredness
• chemotherapy can cause exhaustion, hair loss, constipation, and anaemia
• migraines can cause light sensitivity, headache, sweating, visual problems, and dizziness

When to see a doctor

Nausea in adults often goes away by itself. However if you experience many of the symptoms described above, and they last for more than a few days, consult a medical professional.

Nausea in children is typically more severe, and when accompanied by vomiting or fever, you should always consult a doctor.

Last updated: 24 March 2021