(A/N: Happy Birthday, Sam!)

Hemoglobin

1.

"Hang on, Sam," Dad says. He sounds calm and strong, like he always does, but Sam can see his knuckles on the wheel from here and they're white. "We're almost there, hang on."

Sam tries to reply okay, dad but he chokes and instead lets out a small whimper. He feels something warm and wet speckle his teeth and run down his chin. He tries very hard not to swallow.

"Shit!" And there's Dean, squeezed in the backseat next to him, leaning forward with what feels like all his body weight on Sam's abdomen. "Dad, he's coughing up blood!"

Oh. Sam thinks. Can't have that get on the car.

He forces himself to swallow, wincing at the taste and the thickness as it sluggishly makes its way down his throat. It refuses to go further, stubbornly clinging to his throat until he's forced to cough it all up again and repeat the entire process.

"Sammy," Dean's in his face now, his hands pressing down harder and making Sam gasp again. Dean's knuckles are white too, but so is his face. "Stay with me, okay?"

Sam almost chokes out another okay before he remembers the blood that is trying to escape his mouth and nods instead. Dean doesn't seem to be reassured by that. He stares into Sam's face but directs his words to their dad. "We gotta hurry."

Sam swears he can feel the car lurch forward faster and is thinking about how he can congratulate Dean for giving an order to Dad successfully before he looks down and sees exactly what Dean's hands are doing. He's covering the slash that Sam has received from…shit, whatever they were hunting. Black Dog? Wendigo? It doesn't matter and Sam doesn't care enough to remember. He does think, though, that maybe he shouldn't try so hard to keep the blood from his mouth inside his body when the blood from his stomach is escaping so easily. It's already stained Dean's third-favorite flannel shirt and has made its way onto Dean's hands. Sam swears he can see some under Dean's fingernails, even though the car is dark and his vision isn't that great.

Sam grunts in panic and tries to push his brother's hands away. It translates to weakly tapping at Dean's wrists and has the opposite effect. Dean clamps down even harder, staining his palms and getting flecks of blood on his wrists. "Sorry, Sammy," He says, tremblingly jovial, "We gotta keep as much of this as we can in you. I know it hurts but we gotta."

Sam shakes his head, tries to think of how he can explain. "Hands," He chokes out, tucking his neck in to catch the blood as it drips out of his mouth, before it can ruin the leather. "Dirty…"

Dean sobs out a laugh, nudging Sam's leg with his thigh. "Didn't have time to wash 'em, bro. You're just going to have to deal until we get to the hospital."

Sam's about to explain that, no, that's not what he means, before his vision goes entirely and now all he can hear is his brother's panicked voice. He's going to miss school next week, but he's ok with it so long as the car and his brother can clean up before he goes back.

2.

Sam holds the ice pack to his chest numbly. It's definitely a water pack by now but he can't really bring himself to care.

Not infected…that sure is fucking something, isn't it? Sam could not imagine he would ever be in a position where being zombie-fied by a demon virus was the normal reaction to have. That's just where his life has led to get to this point. Christ.

He glances to the door. Dean is talking to Sarge, all sharp nods and straight lines. This is pure Dean-coming-off-adrenaline and he seems fine.

Dean glances his way, nods briefly at the eye contact, and returns to his conversation. Sam figures this would be the time to ask the question.

"Doctor?" He waits until she turns to him, eyeing the wound on his chest. "Do you have any…theories as to why nothing happened to me?"

She shrugs wearily. "Honestly, I don't think I could give you an answer. Are you sure you actually got infected in the first place?"

Sam swears he can feel the cold steel cut through his skin again. "Yeah. I'm sure."

"Well," The doctor turns back to her samples, fingers tapping a rhythm on the lab table. "If this was a normal virus, first question I'd ask for a lack of reaction would be if you'd been inoculated, or have had any prior exposure to the virus, but obviously…"

Sam makes to snort but it's caught in his throat before it can fully emerge. Suddenly, he is very aware of the blood pumping through his veins. He can hear it echo in his ears and swish around in his brain.

The doctor hasn't noticed his distress. "I mean, the only way you could have been infected but stayed healthy was if your body had prior knowledge of the antibodies needed to fight off the disease. But this isn't a normal situation, so I think it might not hold here."

Sam slams his eyes shut. He tastes something metallic in his mouth. He feels his heartbeat start to quicken, like it's telling him wrong wrong wrong and he hasn't thought to listen before.

"Right," He chokes out, opening his eyes. "Not normal."

He sees Dean glance over at him again. He's the one to nod this time.

3.

"Get up."

Sam shields his eyes, blinking as light floods the room. "Wha—"

His sheets fly off the bed. Before he can react, he's being hauled up with inhuman strength and slammed against the wall of the motel.

"Where have you been?"

Sam groans inwardly. "What does it matter?"

He's being shaken, head bouncing off the wall several more times. He ignores it. "What matters is that we're dealing with a very delicate situation here. I can't help you if I don't know where you are."

"Well, you found me." Sam rests his head back on the wall, leans against it. "Go ahead."

It's not a moment too soon, actually. Beyond his fuzziness he can sense the incoming hangover and it's going to be a bitch. He senses something else too, something larger and achier and bone-deep, but he tries not to think about it.

Suddenly, he's released. Sam collapses onto the ground before he can stop himself, and Ruby sinks down to the ground after him. "I don't think so. I had something for you last night, but you went and disappeared on me."

"Oh come on," Sam tries to lift himself up and decides it's not worth the effort. Instead, he adjusts his posture, makes himself comfortable on the floor. "It's not like we have nothing to work with, here."

Ruby stares at him. "For once, you're right," She says, adjusting herself to her knees and looming over his slumped figure. She reaches behind her and pulls out a knife, then hands it to him with a smirk.

Sam takes it, frowns. "Okay, you want me to…?" He gestures limply to her wrist.

Ruby laughs. "Oh, no," She tells him, smirking. "This is what you get if you disappear on me. You have your own supply, right in you. Use that."

"What?" Sam blinks at her, then smiles slowly. She must be joking. "That doesn't make any sense."

"Oh, no," Ruby pushes herself to her feet. "You see, the trace amounts of demon blood in you can substitute in a quick pinch. It'll do bull for the shaking and the pain and the powers but it'll keep you going for just a bit longer."

Sam stares at her, then back at the knife. "You're shitting me."

"Nope!" Ruby folds her arms and grins at him. It's all teeth. "And I'm not giving you anything until you do it. Think of it as a…reminder not to ditch me again. And who knows? It might save your life someday."

"Hell, no!" Sam drops the knife. He doesn't know if it's purposeful or because his hands are shaking. When did that happen? "I'm not doing that."

Ruby doesn't move. "You don't have a choice. If you want anything, you do this. It's already kicking in and you're desperate enough to need it."

Sam stares at her. He can't even feel the hangover anymore. He just feels the other thing. "Why?"

Ruby inclines her head, but doesn't say anything.

Sam doesn't know how long he lasts, but he ends up picking the knife back up at some point. His coordination is kinda shot so the cut he makes on his arm is jagged, but it bleeds well enough. Keeping his gaze turned down, he lifts up a trembling arm and puts it to his mouth.

Ruby is right. He feels…something change, but it's not enough. He knows he could have an unlimited supply and all this would do is remind him of how little it's helping. He would keep drinking but he would never be satisfied, not even if he bled himself dry.

When the blood hits the back of his throat, reality slams in. Sam chokes, retches, then stumbles to the corner bathroom, bumping his hip on a table as he moves. He spits up into the toilet and thinks that he's never tasted something so disgusting, that he's never done a worse thing in his life.

The bathroom suddenly turns dark. He looks up to see Ruby standing at the doorway, features in shadow. "That's what you get," She tells him and lifts the bloody knife she picked up from the ground. "I can help you now."

4.

Lucifer tells him that he can bring him back, no matter what.

"You keep on trying," He says, smiling gently, right before Sam gasps awake yet again. "It's not going to change a thing. I admire your tenacity, though. Stubbornness is a good look on you."

Sam's hands are perfectly steady as he picks his gun back up from the sheets. He's about to turn it around, try again, when he notices the white bedspread is streaked with red. He looks back and sees that the pillows, bed, headboard, and wall are splattered with blood and brain matter. It looks like a really, really abstract Jackson Pollock painting.

Sam drops the gun. This is going to be hell on whoever has to clean it up later. He should probably find a different way.

He sits up on the bed, suddenly aware of the sticky sensation on his hands and face and suddenly all he wants to do scrub it all off.

Before he can do anything more, his phone rings. Sam covers his bloody hands with his sleeve before he answers it.

5.

"They're purifying me."

Sam hears the desperation in his own voice and hopes that Dean doesn't. He thinks he's unsuccessful, because Dean is looking at him like he doesn't know what to say, like he does whenever Sam has asked Dean to kill him. It's kind of depressing that he can't count the number of times that has happened.

Frustrated, Sam advances forward, trying to ignore his brother's expression and focus on his task instead. Metatron is here…he knows it. He knows it.

He knows it as well as he knows what is happening in his body right now. Okay, so he's fuzzy on the details but he can feel…something searing away in his veins and arteries. The sound of the heartbeat that he's heard his whole life has stopped sounding so wrong, and the heat he can feel instead through his brain and body feels like the reason for that.

Sam's world suddenly tilts and he thinks he's going down again, but it's just Dean.

"Come on, dude," Dean grips his arm, shakes him again. "What's that supposed to mean?"

Sam almost tries to shake him off but holds himself back. "You know," Sam says. "Whatever it is that's happening. It's fixing me. Fixing the demon blood."

Dean's grip tightens. "Okay, there's a lot there that we are going to talk about later but…what do you mean by 'purifying'? Do you know what's happening to you right now?"

Sam blinks, confused. "What do you mean?"

"I mean, do you know what kind of damage the Trials are doing to you?" Dean looks at him steadily. "What makes you say they're 'purifying' you? Which is still bullshit, by the way."

Sam shakes him off this time. "Quit it, Dean. We gotta find the books. And Metatron."

"Sam…"

"I don't know what to tell you man," Sam turns back around, starts to walk again. "I can't say anything except it feels like it's changing my blood. And honestly? I think the only thing that can do is make it better."

He hears Dean gives a sharp, indrawn breath but soldiers on.

+1

"I'm going to need biological siblings." The witch says.

Sam looks at his brother. Dean looks back, clears his throat, and steps forward. "We're brothers."

The witch's face lightens up. "Great! Hunting runs in the family, huh?"

Dean shrugs. "Sure."

"Sit down, then." The witch directs them to her kitchen table. Sam sits, Dean hangs back wearily. "The spell can be broken easily enough, just need some blood from you both." She scoffs something about "amateur spellcasters" and "ruining it for the rest of us" but it's lost in the shuffle of her ingredient gathering.

She suddenly turns back to them as if struck by a thought. "Wait, do you guys have the same mom and dad? Not half-siblings?"

"Nope," Dean finally sits, although he's still eyeing the witch suspiciously "Full brothers."

"Perfect." The witch returns and dumps all her spell-casting items on the table. Sam thinks he can see a frog leg poking out of one of the jars. She hands them a bowl and a knife. "I'll do basic prep here. You guys just need to give me a bit of blood each."

She begins to grind something together with a mortar and pestle. Dean takes the knife and side-eyes it. "Why should we trust you?"

The witch doesn't even hesitate. "I really don't want this town to be overrun with any kind of evil. I live here too, you know. Just because I practice in the privacy of my own home doesn't mean I agree with everything every other witch does."

Dean glances at the knife, and then at Sam. Sam shrugs, gestures towards him. Your choice.

Dean sighs, closes his eyes for about a minute, then comes to a decision. "Fine." He pulls the bowl closer towards him and flips his palm up. "How much do you need?"

"Not too much." The witch is now liberally tossing in herbs into a mixing bowl. If he didn't know better, Sam would say that she was making a particularly weird salad. "Just enough to barely coat the bottom of the bowl. From both of you combined."

"Oh, is that all?" Dean snipes, rolling his eyes. He grips the knife hard and slashes it quickly across his palm, shaking it over the bowl. Blood begins to drip slowly from his hand.

Sam clears his throat. "Why do you need siblings for this?"

The witch beams. "It's pretty fascinating, actually. Okay, so you know how your DNA is determined by a combination of your mother and father, correct?"

Sam nods. Dean shrugs, his eyes still on the bowl. "Sure."

"So you're half your mom and half your dad. But if you have siblings, they're half-and-half of the same stuff too. For parents and kids and half-siblings, you only share about 50% of yourself. But for siblings, you share 100% of the same thing. It's a little complicated but in simple terms, you guys have the same set of DNA in you, it's just that they're activated in different combinations. You have the basic instructions of each other in your blood, pretty much. And so siblings are the closest you can get to finding yourself in a different person."

Dean's finished with the bowl and slides it over to Sam. They make brief eye contact, then Dean looks down and hands him the knife.

"And lots of curse-breaking asks for all sort of impossible shit because witches just love to be complicated," The witch dumps something gooey in the mixture and starts to stir it methodically, one clockwise, twice counter clockwise. "One of which happens to be something like 'the blood of two that are also one' which I know some smarmy asshole thought would be impossible to actually do. But they didn't know shit about DNA or anything back then so they had no idea that siblings technically can satisfy that requirement. Honestly, if more witches just read up on some basic science, you guys would have a lot more problems."

Sam makes to cut himself, then hesitates. "Hey," He says, interrupting her. "Would it maybe be a problem if, well…"

The witch looks up at him. "Yes?"

He can't bring himself to look at Dean. "If one person's blood is, like…infected? Or tampered with? Or like…mixed with something demonic?"

He can feel Dean's eyes on him, can almost sense him take a breath, as if he's about to say something. But Dean stays silent and Sam can't bring himself to look and see what he's thinking.

The witch's brows are furrowed. "All that matters is you're related by blood. All that extra stuff: illness, or, like, possession or whatever you're referring to doesn't hold any ground. All that matters is the DNA. All that other stuff is just window dressing."

Sam's grip tightens on the knife. "Are you…?"

"I'm sure." The witch puts down her spoon, then pulls out an electric blender. "For this, blood is just blood. We're looking for what's deeper."

Sam's mouth goes dry. He finally glances to his left, where Dean is sitting. Dean's looking at him, frowning slightly, then gestures at him. Go for it.

Sam makes the cut and watches the blood drip past his fingers in long, thin rivulets. He's suddenly struck by the fact that it looks like Dean's, which makes absolutely no sense but he can't shake the feeling.

"It's just blood, Sam." Dean repeats quietly. He looks like he's about to say more but he doesn't, just tosses him a look that feels ten layers of loaded and Sam doesn't think he has the capacity to sort through all the meanings.

He looks back down at his hand and finds he doesn't feel…well, much of anything when he looks at the red dripping from his hands, just impatience and tension and the hope that they can get through the hunt with as many lives saved as they can.

"Yeah," Sam says, looking up and giving Dean a small smile that feels real. "Yeah, I know."

END