Tension headache and dehydration: what to know

Not drinking enough, sweating, vomiting, diarrhoea, fever, or prolonged heat exposure can leave you dehydrated. Headache may occur alongside thirst, dry mouth, darker urine, tiredness, dizziness, or reduced urination. Muscle fatigue and heat stress can also increase neck and scalp tension. These clues can support dehydration as a contributor, but they cannot confirm that explanation; headache can continue after fluids if another trigger or condition is present.

Move to a cool place, rest, and take small, regular sips of water. If fluid loss followed vomiting, diarrhoea, or heavy sweating, ask a pharmacist or clinician whether an oral rehydration drink is suitable. Replace food gently when you can tolerate it and avoid alcohol while recovering. Do not force large amounts quickly, particularly if you have a condition that limits fluid intake; seek personalised advice instead.

Seek urgent help for confusion, fainting, severe weakness, inability to keep fluids down, very little urine, a sudden severe headache, or headache with weakness, speech trouble, seizure, fever and neck stiffness, or a head injury. Arrange medical advice if symptoms do not improve after rest and sensible rehydration, or if dehydration followed ongoing vomiting, diarrhoea, or heat exposure.

Ask how much fluid is appropriate for you, whether medicines or an existing kidney or heart condition affect rehydration, and whether your headache pattern suggests another cause. Mention fluid losses, urine changes, dizziness, fever, and any pain medicine used.