What should you know about constant headache and thirst?

Thirst and headache can follow sweating, fever, diarrhoea, vomiting, missed fluids, or a dry environment. [Dehydration](/conditions/dehydration/) can also cause dark urine, tiredness, dizziness, and a dry mouth. A respiratory illness may reduce drinking while increasing fluid needs. Persistent thirst, frequent urination, blurred vision, unusual tiredness, or weight change needs a clinician’s review because the combination may have causes beyond simple fluid loss. Symptoms alone cannot establish a diagnosis.

Rest somewhere cool and drink fluids gradually if you are awake and swallowing safely. Replace normal meals when able, and avoid using very sugary drinks as the only source of hydration. Note urine colour and frequency, recent sweating or illness, medicines, and how much you have been drinking. Arrange a clinical appointment if thirst and headache continue despite sensible fluid intake, recur often, or interfere with sleep or daily activities.

Seek urgent care for confusion, fainting, inability to keep fluids down, very little urine, severe dizziness, breathing difficulty, chest pain, a sudden severe headache, new weakness, or a seizure. After heavy heat exposure, move to a cool place and seek help for worsening symptoms, especially if you cannot drink normally. [Heat Exhaustion](/conditions/heat-exhaustion/) can require prompt treatment.

Tell your doctor when the thirst began, whether urination changed, and whether fever, vomiting, diarrhoea, sweating, or a new medicine was involved. Ask whether you need an examination or blood and urine checks, and how to manage fluids safely. Mention recent travel or infection symptoms; [COVID-19](/conditions/covid-19/) and [Dengue Fever](/conditions/dengue-fever/) may be relevant depending on the wider picture.