The headache that turns out to be dehydration — the long version

Headache is one of those subjects where the general answer and the answer for a specific case diverge, and the thread will go in circles until someone says which one is being asked for.

Answering the question post #29 raises rather than the one it answers.

Commercial rehydration formulations are designed for a specific purpose and are not equivalent to a sports drink, whatever the marketing suggests.

Everything in post #33 holds. The case it does not cover is the one I have.

Cramping is the symptom most confidently attributed to electrolytes and has the weakest evidence linking it to them.

The confident version of this sentence would be wrong, so here is the hedged one.

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

I am not the right person to answer the follow-up to this.

Orthostatic symptoms: dizziness on standing after lying down can indicate dehydration or electrolyte depletion. Increasing fluids, salt, and potassium usually resolves it.

The most useful posts here describe what was measured, what was changed, and what happened, in that order.

The uncertainty is in the assumption, not in the calculation.

Rapid correction of a genuine abnormality can be more dangerous than the abnormality, which is another reason this belongs in clinical hands.

Adding a source would improve this post and I do not have one to hand.

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

I would put a moderate confidence on that and no more.

Post #67 answers the question as asked. The question underneath it is different.

The confident answers on headache and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.