Twilight laid a hoof on Spike as they sat in the waiting room of the Ponyville Hospital. "How are you, Spike?"
Spike looked at Twilight, bleary-eyed. "Head still hurts...so dizzy..."
He was slumped back in the waiting room chair, looking half-asleep. Twilight's worry for her Draconic friend and assistant grew with every moment. She should have done something sooner, back when she first noticed his lethargy. She thought it was just a Dragon thing, a symptom of puberty alongside his recent growth spurt. Later came the bouts of weakness, occasional headaches and dizzyness, which they both thought was a sign of overwork. Despite resting for a day or two, he only seemed to get worse. When the headaches and dizzyness wouldn't go away and Spike's scales started looking pale, Twilight decided it was time to take him to the hospital.
Finally, Nurse Redheart called Spike's name, and the two of them followed her out of the waiting room. After the usual initial weight, temperature and blood pressure readings were taken, and Spike's relevant medical information was confirmed or updated, the Nurse left, the Doctor entering a few minutes later. Doctor House Call was a middle aged stallion, with a wavy brown mane peppered with gray, and stubble long enough to be called the beginning of a beard, likewise about to go from brown to gray. He had a coat of white with brown spots, His cutie mark showed a stethoscope with a question mark overlapping it. As usual, he had a perpetual scowl of annoyance. He walked in with his usual limp, one foreleg wrapped around the cane that he leaned on.
"Your Majesty." He spoke in a neutral tone laced with sarcasm. "Forgive me if I don't kneel, the leg's not what it used to be."
Ignoring House's snark, Twilight explained the situation and Spike's symptoms, while House nonchalantly looked the Dragon over. Finally, after Twilight finished her description of Spike's symptoms, House sighed. "Feed him some chunks of iron and he'll be fine."
At this, House turned to leave, but Twilight said after him, "Wait, what?"
House sighed again, and turned to face Twilight. "Iron. 26th element of the periodic table, notable component found in blood. Too much of it, you die. Too little of it, you die. in his case..." he motioned to Spike, "It's the latter."
Again, House prepared to leave, but again, Twilight spoke, "I don't understand, Doctor...why does he have an iron deficiency?"
House retorted, "Because he's a Dragon, and I'm guessing you're feeding him like a Pony."
Twilight scowled, offended. "I DO feed him like a Dragon! He eats gems and a high protein diet..."
"And I'm sure it worked just fine when he was a child." House interrupted, "But judging from his lanky appearance, I'm assuming he's just hit a growth spurt. Meaning larger size and changing body chemistry...meaning he needs to be fed differently."
He pointed to Spike's mouth. "Here's a hint: Those fangs aren't just there to make him look scary."
Twilight fumed at House, but managed to keep her patience, as she knew he was right, and she berated herself internally for not seeing it earlier. "Fine...but why chunks of metal?"
"He needs a lot of iron quickly." House answered, "If Dragons can chew diamonds, then digesting metal's a breeze."
Twilight nodded. "Thank you, Doctor." She said, despite herself. House merely limped off, muttering some lament about "Clinic Duty."
Two hours later, Spike managed to swallow the last of another piece of pig iron that used to be one of their cooking skillets. Afterwards, Twilight gently led Spike to his room in their crystalline castle home by allowing him to lean on her while also supporting him with her magic. She helped him to get into his bed, nuzzling him.
"Just rest, Spike." Twilight said with a warm smile, "We'll just feed you lots of iron like the Doctor said. You'll be just fine."
Spike smiled back and nodded. Twilight draped a blanket over him gently with her magic and kissed him on the cheek. "I love you, Spike."
"I love you too, Twilight." Spike said, yawning. Not wanting to leave the side of her LBBFF (Little Brother Best Friend Forever), the Alicorn Princess climbed into Spike's bed, snuggling close to him.
After two days of a steady high iron diet from both ferrous metal utensils and whatever ore rich rocks could be found, Spike was finally looking as healthy as ever, his scales back to their normal color. He picked up a shaker of rust flakes, dashing them onto his spaghetti like a spice.
"The meat supply from Griffonstone should arrive tomorrow, Spike." Twilight spoke, before slurping up her noodles.
"Good thing, too..." Spike said, "Iron's fine as a garnish, but by itself, yeeeuuchh! And they really need to rename Pig Iron, it doesn't taste a thing like pork!"
Twilight laughed.