It could be dehydration. If your bladder is full, your bloodstream my be short of fresh water. I get headaches before I actually feel thirsty. Propel seems especially helpful with this -- in the heat it beats plain water for me.
Except that it diminishes after I urinate, whether or not I also drink anything. (Though yeah, I've had dehydration-related increases in headache pain also, so that's a reasonable conjecture in the absence of this clarification.)
(no subject)
(no subject)
It does seem I'm not alone, anyhow ...