Feeling sick after eating: causes, red flags and when to get it checked

Occasional nausea after a large, rich or rushed meal is very common and usually settles by itself. Persistent nausea that follows eating, particularly if it comes with pain, bloating, vomiting or weight loss, is worth getting looked at, because the cause can be anywhere along the digestive tract, from the stomach to the gallbladder and pancreas.

The NHS describes feeling sick as common and usually going away on its own. Its practical advice is to see a GP if you do not feel better after a few days, or if the sick feeling keeps coming back. A GP can look for the cause and suggest treatment, including anti-sickness medicine if it is needed.

This page is about nausea that is clearly linked to eating. If your nausea is mostly first thing in the morning, or happens with no relationship to food, the more general nausea and morning nausea pages on this site cover those patterns.

The causes below are the ones named in NHS pages. They overlap, and it is not unusual for more than one to be present, so this is a guide to what the pattern suggests rather than a way of diagnosing yourself.

The NHS says indigestion is often caused by acid from the stomach irritating the stomach lining or throat. It can be caused or made worse by certain foods and drinks such as coffee, tomatoes, alcohol, chocolate and fatty or spicy foods, by being overweight, smoking, pregnancy, stress and anxiety, some medicines including anti-inflammatory painkillers such as ibuprofen, and a hiatus hernia.

For most people the first steps are the ones the NHS lists: cutting down on tea, coffee, cola and alcohol, raising the head and shoulders in bed, losing weight if overweight, avoiding rich, spicy or fatty food, not eating 3 to 4 hours before bed, and not taking ibuprofen or aspirin unless prescribed. A pharmacist can suggest antacids, alginates or proton pump inhibitors.

An open sore in the lining of the stomach can cause the same picture. The NHS names infection with Helicobacter pylori bacteria and regular use of anti-inflammatory painkillers as the main causes of stomach ulcers, with the main symptom being upper tummy pain that may feel like burning and is often worse at night. Because ulcers can bleed or perforate, the NHS says treatment matters.

Gallstones are common and often cause no symptoms. The NHS explains that when a stone blocks a bile duct it can cause biliary colic, a severe and constant pain that lasts longer than 30 minutes and may make you feel sick or vomit. It names being over 40, being a woman, living with obesity, a diet high in fat and low in fibre, and rapid weight loss as factors that make gallstones more likely.

Gastroparesis is a long-term condition in which food passes through the stomach more slowly than it should. The NHS says symptoms start after eating and may include feeling full sooner than usual, nausea and vomiting, tummy pain, heartburn and bloating, and that weight loss can follow. It can be linked to diabetes or occur after some types of surgery.

Chronic pancreatitis is a less common explanation, and mainly affects adults who drink or smoke heavily. The NHS describes pain in the upper tummy that is often worse after eating, with nausea or vomiting, diarrhoea, very smelly poo that floats, and unintended weight loss. It notes that symptoms can resemble irritable bowel syndrome or gallstones, which is why a GP may need to rule other causes out first.

A food intolerance means difficulty digesting a food or ingredient. The NHS says symptoms usually appear a few hours after eating the food and commonly include diarrhoea, bloating, wind and tummy pain, though nausea, tiredness and headache can occur. Lactose intolerance is the most common, and the NHS notes its symptoms can start a few minutes or a few hours after dairy.

A food intolerance is different from a food allergy. Allergy symptoms such as swelling of the lips, face or throat, difficulty breathing or a raised itchy rash are an emergency and need 999. The NHS also advises against home tests that claim to diagnose food intolerances, saying there is limited evidence they are accurate and that they may lead you to avoid multiple foods, which can be harmful.

A food and symptoms diary is the practical tool the NHS suggests. Writing down what you ate, when, and what followed helps a GP or dietitian see whether a pattern exists. Cutting out foods without advice risks missing vitamins and minerals.

Most nausea after eating is not dangerous, but a few features should not be waited out. The NHS advice on indigestion and stomach ulcers can be summarised as follows.

• See a GP if you keep getting indigestion, are in severe pain, have lost a lot of weight without meaning to, have difficulty swallowing, keep being sick, have iron deficiency anaemia, or feel a lump in your stomach.

• Ask for an urgent GP appointment or call NHS 111 if tummy pain is getting worse or not going away, you feel full after a very small amount of food, you have lost your appetite, or you are tired all the time.

• Call 999 or go to A&E if you vomit bright red blood or something that looks like ground coffee, your poo is black, sticky and very smelly or has blood in it, you have severe tummy pain or a tummy that is painful to touch, or you have sudden chest pain.

• For suspected gallstones, the NHS says tummy pain lasting longer than 30 minutes needs an urgent GP appointment or NHS 111, while sudden severe pain, pain spreading to the back with being sick, a very high temperature or yellow skin or eyes needs 999 or A&E.

A GP will ask when the nausea starts in relation to meals, what you eat, which medicines you take (including over-the-counter anti-inflammatories) and whether you have lost weight. They may feel your tummy and weigh you.

Depending on the picture, the NHS says tests may include a breath, stool or blood test for H. pylori, blood tests, an ultrasound scan for gallstones, an X-ray or scan of the stomach, and a gastroscopy, where a thin flexible camera is passed through the mouth into the stomach. Treatment depends on the cause: acid-reducing medicines and antibiotics for H. pylori, surgery to remove the gallbladder for troublesome gallstones, dietary changes and medicines for gastroparesis, or avoiding the food responsible for an intolerance.

Until then, the NHS suggests simple measures for nausea itself: fresh air, small sips of a cold drink, ginger or peppermint tea, smaller and more frequent meals, eating slowly, avoiding strong-smelling, hot, fried or greasy food, not having a large drink with meals and not lying down soon after eating.