The headache that turns out to be dehydration

The headache that turns out to be dehydration Writing it up because I had to work it out twice and would rather nobody else did.

Reporting what I changed and what happened, with the caveat that I changed two things at once and therefore know less than I would like.

Over 15 weeks: fluid up, salt up, both by an amount I recorded. Symptoms improved. I cannot separate the two changes and I cannot rule out that it would have settled anyway.

How would you design this so the next person gets an answer rather than an anecdote?

Following, with nothing to contribute beyond having asked the same thing elsewhere.

Confirming post #43 from a second method, which matters more than confirming it from a second person.

For anyone finding this later: the short answer on headache is that it depends on one thing, and the rest of the thread is people identifying which thing.

Vomiting and diarrhoea lose fluid and electrolytes together, and replacing only fluid is what turns a short illness into a longer problem.

Post #65 answers the question as asked. The question underneath it is different.

The practical version of headache is three sentences long. The rigorous version is three pages and reaches the same conclusion with the conditions attached.

Adding salt to food is the intervention most consistently reported as helping and is also the one least likely to cause harm.

The mechanism is plausible, which is not the same as established.

Picking up post #109: that is the part I would want checked first.

The number people quote for headache is a central estimate presented without its interval, and the interval is wide enough that the estimate is nearly uninformative on its own.

Post #127 put the caveat in the right place and I want to underline it.

The version of headache that I was taught turned out to be a teaching simplification. Useful, and not true in the way I had assumed it was.

Worth stating the null on headache before we explain it: the observation may be nothing. That possibility deserves a sentence and usually does not get one.