John wasn't concerned when, one day after finishing his tea and reading the newspaper, he passed out when he got up.
"Must have been too quick," he said a moment later, when he was lucid. "I suppose I'm not as young as I used to be."
Sherlock, who'd rushed to John's side when he heard the thump, snorted. "As ever, you state the obvious."
John grinned wickedly. "Shut up. Neither are you."
Sherlock's grin faded. "Are you sure you're fine though? Syncope can be a symptom of a number of different things, including-"
"Sherlock," John said gently. "I got up rather quickly. There's nothing wrong me with that going more slowly won't fix."
Sherlock frowned, but nodded.
Still, he kept a close eye on John every time he got up from the couch for the next couple of weeks.
John didn't pass out as he got up in the next few weeks, but he did arrive home from shopping with the beginnings of a bruise on his forehead.
"Had a row with the chip and pin machine," he told Sherlock. "It definitely won."
Sherlock frowned. Lies.
But he let it go.
And he let it go when John forgot to get milk.
And then the next week when he forgot it again. And again.
(The fourth week would have been the last straw, but he remembered it then.)
And he let it go when John seemed unable to remember where they kept the tea cups. (It was early after all, just pushing 5am, and Sherlock had a habit of moving them.)
And Sherlock let it go when John broke up with his latest girlfriend (he claimed, Sherlock could tell she broke up with him) because there wasn't any emotion in it.
When they ended up in A&E because John had fallen over nothing ("It was a kerb, Sherlock," John had insisted), fearing a broken wrist, Sherlock called the doctor. He was done with letting things go. Things had gone on long enough.
He threw the card with the appointment date and time at John back at the flat, with a diagnosis of a bad bruise. John sighed, but knew there was no point in fighting it. Sherlock would ensure he got there, whether it was of his own volition, or against his will.
And he'd prefer not to be drugged in all honesty.