What causes nausea?

Nausea can be caused by stomach infections, food poisoning, medicines, migraine, motion, dehydration, low blood sugar, pregnancy or other medical conditions. It is the uncomfortable urge to vomit, and it may occur with or without vomiting. The cause is easier to narrow down when you consider what happened before it began and which symptoms appeared alongside it.

Digestive causes include gastroenteritis, food poisoning and irritation of the stomach lining such as gastritis. Upper abdominal pain after meals can occur with gallstones. Fever, diarrhoea or vomiting makes an infection more likely, while a severe headache, light sensitivity or visual changes can accompany migraine. Heat exhaustion and dehydration may bring nausea with thirst, weakness, dizziness or heavy sweating.

Nausea can also follow a new medicine, alcohol, anxiety, strong smells, travel or pregnancy. Low blood sugar may cause nausea together with shakiness, sweating, hunger, weakness or confusion, particularly in someone using diabetes medicine. Less common causes include problems affecting the liver, brain or other organs, so persistent or unexplained symptoms deserve assessment.

Take small, frequent sips of water or an oral rehydration drink. Rest somewhere cool, avoid alcohol and limit strong smells. When you can eat, try small portions of plain foods and avoid heavy, fatty or spicy meals until your stomach settles. Move slowly if you feel dizzy.

Review any recently started medicine with a pharmacist or clinician, but do not stop a prescribed medicine without advice. If diabetes medicine may be involved, check your blood sugar if you can and follow your personal sick-day or low-sugar plan. Pregnancy, repeated episodes or nausea lasting more than a short period may need targeted treatment.

Get urgent medical help for severe or worsening abdominal pain, chest pain, a severe headache, a stiff neck, fainting, confusion, trouble breathing, blood or green material in vomit, or signs of severe dehydration such as very little urine and marked weakness. Seek prompt advice if you cannot keep fluids down, symptoms follow a head injury, or you may have swallowed a harmful substance.

Arrange a medical review when nausea keeps returning, lasts longer than expected, comes with unexplained weight loss, yellowing of the skin or eyes, persistent fever, or begins after a new medicine. Children, older adults and people with significant medical conditions can become dehydrated sooner and may need earlier advice.

Ask what causes best fit the timing, accompanying symptoms and medicines you take. You can also ask whether you need tests, how to prevent dehydration, which foods or medicines to avoid temporarily, and which warning signs should prompt urgent care.