Is Hourman only able to take one pill a day, or is it that he has to wait an hour between pills? I’ve read both online. One a day is still interesting, but not as impressive.
If he turns into Four-Hourman, he needs to call his doctor. 
There have been two main Hourmen, multiple canonical reformulations of Miraclo, and a whole buttload of writers, over the ~70 years that Hourman has existed.
I’m pretty sure every possible way of doing it has been done.
The most recent that I can recall, I’m pretty sure he could take another dose as soon as the last one was worn off - the drawback was an addiction problem.
Well, in comics there’s no short supply of folks called “Doctor.” Not sure I’d want to consult Dr. Doom about that sort of issue, though. 
Hey, both Hourmen were on the team with Drs Mid-Nite. They totally had physicians right there.
Yeah, but a blind doctor? That’s like hiring a blind lawyer or a wimp as a reporter. Totally unsuitable for the job.
There was even one story where he had a concussion and lost track of how much time he had left on the dose he took. He fought the bad guys, won, and discovered the pill’s effects had lapsed before he woke up again.
I’d count the android Hourman (the only one to carry a monthly title, I think) as a “major” Hourman.
DOOM is concerned about your sodium levels. You should cut back on salt. SUCH IS THE WILL OF DOOM!
On a related topic, would working out while he’s using the Miraclo make him more fit than a normal person, since he’s lifting incredible weights?
This was well after the character’s initial heyday, though. The story was actually titled “Whatever Happened to Hourman?”, from DC Comics Presents #25 (September 1980). Hourman was the first character chosen for the “Whatever Happened to…?” backup feature, which ran intermittently until issue 48 with various golden- and silver-age characters whose publication had lapsed, though many (including Hourman) would soon be revived in All-Star Squadron in mid 1981.
I would think it would depend on what the Miraclo was actually doing to his body.
If it was letting him ignore a certain amount of pain and upping his adrenaline, so he could push harder, without actually altering how his muscles were working, I could see it working.
If it was actually making him super strong, not so much.
I’m pretty sure the latter is canon, or at least closer to, so…
He was kind of a big deal in the 60s, with the “Hourman and Dr. Fate” series in Brave and the Bold. I couldn’t stand the younger version, married to Jessie Quick.