Alcohol and dehydration

Risk rises when drinking is combined with hot weather, sweating, vomiting, diarrhoea, or strenuous activity. Thirst, dry mouth, headache, dizziness, tiredness, and darker urine can occur, but symptoms should be considered together rather than relying on urine colour alone.

Alcohol suppresses a hormone that normally helps the kidneys conserve water, so the body may pass more urine. It can also impair judgement, disturb sleep, and cause nausea, making regular drinking and eating less likely.

Dehydration is not the only explanation for feeling unwell after alcohol. Low food intake, poor sleep, medicine interactions, infection, and alcohol poisoning can produce overlapping symptoms. Cloudy urine, burning urination, fever, or flank pain may point to another problem that needs assessment.

Stop drinking alcohol and move to a cool, safe place. Take frequent small sips of water; an oral rehydration solution can replace salts as well as fluid when vomiting or diarrhoea is present. Eat a light meal if you can tolerate food, and avoid strenuous exercise until dizziness and weakness settle.

Do not force large amounts of fluid quickly if you feel nauseated. Someone who is very drowsy, confused, or vomiting repeatedly should not be left alone or given drinks when they cannot swallow safely.

Call emergency services if a person is difficult to wake, confused, having a seizure, breathing abnormally, fainting, or unable to protect their airway. These may signal alcohol poisoning or another emergency rather than simple dehydration.

Seek prompt medical advice for persistent vomiting, inability to keep fluids down, very little urine, severe dizziness on standing, worsening weakness, blood in vomit or stool, marked abdominal or flank pain, or symptoms after prolonged heat exposure.

Describe how much and how often you drink, fluid intake, heat or exercise exposure, vomiting or bowel symptoms, urine changes, and all medicines. Ask whether kidney function, infection, blood salts, or another cause should be checked, especially if episodes recur.