Disclaimer: Supernatural and its characters are the property of Eric Kripke. Sadly, I do not own any of these guys.

A/N: This was written as a fill for a prompt on LJ. The prompt was as follows:

"I want one of the Winchester brothers to donate something to the other. It can be anything from blood or bone marrow to a kidney or something more. Today I started thinking about Dean knowing that he's going to die (at the end of s3) and thinking about how instead of getting ripped apart by hell hounds, he could die a few hours earlier, not go in pain and donate his organs to those that need them. (It was becoming this whole Faith AU where Sam was the one with the bad heart)…"

It wasn't until after they'd finished setting fire to Adam's body – his real body, not the ghoul's – that Dean noticed something wrong with Sam. It barely registered at first: Sam swayed a little on his feet, his eyes staring somewhere off into the distance even though it was too dark to see anything, and groaned just barely loud enough to hear. Dean probably wouldn't have noticed those things at all that night, except barely a second later Sam's eyes rolled up in his head and he started to fall backwards, barely saved from falling onto Adam's funeral pyre by Dean's quick reflexes.

"Sam! What the hell?!" Dean growled as he lowered Sam to the ground, startled and not in the mood to deal with any more drama for today. "I know you're tired, but this is not the time to –"

He stopped mid-sentence, every horrifying piece of this puzzle beginning to click into place and making him realize how terribly distracted he must have been not to notice this earlier. Cursing, he pulled up the bottoms of Sam's sleeves, which were saturated with blood, and revealed the deep gashes the ghouls had cut into his wrists not two hours before. As he feared, they were once again bleeding sluggishly down Sam's hands, dripping crimson onto the younger Winchester's pant legs where they hung over them.

Dean could've kicked himself right then, if he thought it would have helped. He was really failing this time in the "Watch out for Sammy" department, that was for sure. Sam had almost bled out in that house earlier, had lost enough blood to make him obviously weak and disoriented, and what had Dean done? Told him to "keep pressure on that."

Yeah, sure, thanks Dr. Asshole. Of course Sam would have thought of that before! These were bad enough cuts that, had he been in his right mind and not consumed with grief and jealousy over realizing what a liar their father had truly been, Dean would usually have immediately stitched them then and there, not told Sam to "keep pressure on them." To make matters worse, he'd even made his wounded brother help carry Adam's body and set up the wood for the fire; that surely hadn't done anything to help.

"Alright, Sammy, let's see," Dean said softly, saving the self-guilt-trip for later, when he was sure his little brother was okay. He pressed two fingers to the pulse point beneath Sam's jaw, his own heart beginning to race when he felt how fast and weak and thready Sam's pulse was. Lubdub-lubdub-lubdub-shocky-shocky-shocky…

"Dammit," he muttered, running his palm down Sam's forehead and cheek and grimacing at how pale and clammy he was. When he groaned and started to shiver under Dean's hand, the older Winchester knew this was already way past the point of being dangerous. He'd heard once that anything over about two and a half pints of blood loss would start leading to shock, and that anything over four could be fatal. He didn't know exactly how much blood Sam had lost, but he knew it was a lot and that Sam was on his way to death if something wasn't done fast.

"Okay, Sammy, come on. Up and at 'em," he said gently, trying to keep the quaver of fear out of his voice and shaking Sam ever so slightly in an attempt to rouse his unconscious brother.

"Mmnnh? Deee?" Sam mumbled, eyes cracking open ever so slightly at the sound of his brother's voice.

"Atta boy, Sam," he encouraged, given a little bit of hope by the fact that Sam was at least still responsive. "Come on, I need you to stand up for me, little bro."

Sam blinked slowly at him and then did his best to comply, letting Dean guide him up on legs as shaky as stilts and leaning against his older brother to keep from tumbling face-first to the ground.

"D'n, wha- Wha'ap'nd?" he slurred, lips refusing to form the words properly through his obvious exhaustion.

"You lost a lot of blood, Sammy. Those ghouls got you a little worse than I thought."

"Ohh… M'tired…"

"I know. You're startin' to get a little shocky on me, I think. Just stay awake until we get to the car, okay?"

"'kay…"

They walked in silence for a little while longer, Dean completely focused on keeping Sam's feet stepping one in front of the other while he supported his enormous bulk. Finally they reached the Impala, and Dean had almost gotten them to the passenger door when Sam suddenly balked, feet planted as he straightened up and closed his eyes.

"Sam?" Dean asked, not liking the pinched, pained look on his brother's face. "What's the matter?" Besides the obvious, of course.

"Dizzy… feel sick…" Sam moaned, gagging after the last word.

"Whoa, hey, easy," Dean said quickly, opening the door and guiding Sam to sit down on the passenger seat with his feet on the ground outside and his head between his knees. "Just breathe through it, Sammy, okay? Easy, just breathe…" Sam was already low enough on fluids as it was; vomiting would only make it exponentially worse.

Dean rubbed circles on Sam's trembling shoulders, trying to get his brother's stomach to settle and to slow down his borderline-hyperventilating breaths, knowing it was likely a losing battle. Sam was only going to get worse without help, and help was back at the motel, twenty miles from here. If it weren't for the fact that the cuts were on both of Sam's wrists, Dean would have rushed him to the ER immediately. But that was likely to get the younger Winchester locked up in a psych ward somewhere that Dean couldn't get to him, and the second he started mentioning angels and the Apocalypse? Well then Dean could just about count on never seeing his little brother again.

So he did the only thing he could, and waited by Sam's side until he looked like the urge to be sick had passed. Then he quickly but carefully got Sam settled in the car and raced around to the driver's side, turning it on and peeling out of the woods faster than he would have with a Hellhound on his heels. He hoped there weren't any cops out on these little dirt roads tonight, because there was no way he was stopping for them until Sam was out of danger.

About a mile away from the place where Adam lay burning, Sam started shivering violently, curling up as tightly as he could while chills racked his entire body. Dean cursed to himself, recognizing another symptom of severe shock, and turned up the heater as high as it would go. He aimed all of the warm air at his little brother and pulled him up against his side, taking off his coat and throwing it over them both before wrapping his free arm around Sam's back to hold him close. Sam sighed gratefully, teeth still chattering as he pressed himself up against Dean and buried his face in his chest, seeking out warmth anywhere he could get it.

"It'll be okay, Sam. Just hold on," Dean whispered, and pushed the gas pedal to the floor.

By the time they reached the motel, after a ten-minute drive that should have taken thirty, Sam had completely lost consciousness again and nothing Dean did was able to rouse him. He had stopped shivering quite so hard too, which Dean wanted to think was because of the Impala's heater and not that Sam's body was slowly giving out on him.

As soon as he'd thrown the car into park, Dean got out and unlocked the motel door, propping it open with a metal trashcan before turning on the light and going back to get Sam. His little brother was heavier than he remembered – it felt like he'd put on at least fifteen pounds of muscle since Dean had been in Hell – but he managed to get him inside eventually and deposited him on the bed closest to the door, covering him up with several blankets but leaving his arms exposed so they could be stitched. It wouldn't do any good to give Sam any blood or fluids if the cuts weren't closed first.

It didn't take him long to find the med kit, and he soon had it set up beside Sam's prone form, pulling out a bottle of alcohol and some cotton balls to clean the cuts with before he sewed them shut. Sam whimpered and twitched at the first sting of alcohol inside the deep wounds.

"Sorry, Sammy, sorry," Dean said softly, waiting until his brother had stilled again before pinching the edges of the first cut together and beginning to stitch. It didn't take him long to get it closed, seeing as the two of them had sewn themselves and each other so many times before, and within ten minutes he had both of Sam's wrists cleaned, stitched, and wrapped in clean bandages. That task completed, he moved on to the more important one: replacing some of the blood his brother had lost.

They didn't have any real equipment for blood transfusions – that kind of thing wasn't exactly easy to come by without a medical license, and those were too hard to forge – but luckily for Sam they did have a couple of 50cc syringes they'd stolen from hospitals and veterinary supply stores over the years, as well as some IV fluids and the catheters used to administer them. Dean thanked whoever was listening that he'd lucked out and ended up with O-negative blood, because otherwise A-positive Sammy would've been completely out of luck.

"Alright, little bro, let's get you fixed up, huh?" Dean muttered, mostly to himself since Sam likely couldn't hear him. His hands held steady as he found a suitable vein on the inside of Sam's elbow, cleaned the skin and inserted the IV catheter, taping it into place once he was sure he'd hit the right spot. He hooked another one to the other arm, this one full of saline, and set it to a slow, steady drip. Then he took a deep breath; this next part was really gonna suck.

Dean had given fluids to people a few times in his life, but giving his blood to someone else through an IV was something he'd only done once, when John had been badly cut up by a Wendigo. As a ten-year-old, he hadn't been too happy about being stuck with huge needles over and over again just because his blood type was the only one that John, also O-negative, could take. But at least then he'd had Sam to watch in fascination, thinking what a hero his brother was for giving blood to their dad while Bobby coached him through the process. This time, he was completely on his own.

Trying not to wince prematurely at how big the needle was, he took it firmly in his hand, easily tapping into one of the veins in his own left arm once he'd flexed the muscles enough to make it stand out more. The enormous syringe was longer than his hand from wrist to fingers but filled up quickly, and before he'd even given the puncture time to seal he had stuck it into Sam's open IV port, slowly pushing the blood through so he wouldn't accidentally blow the vein and have to start again. His technique wasn't sterile by any means, but Sam was going to need some antibiotics for those lacerations anyway, so at this point what did it matter?

He repeated this process again and again: stab, fill up, stab, empty out, stab, fill up, stab, empty out, pushing hot water through the syringe several times whenever it got too clotted with dried blood. It didn't seem to have much of an effect at first, but by the tenth repetition Sam was regaining a little of his color, his shivers abating and his breathing slowing down to a more normal rate. By the twenty-fourth and final syringe full, just over two and a half pints of blood, Dean was starting to get dizzy, and he sat down on the bed beside Sam and breathed through a head rush, checking his brother's pulse and smiling when he realized it was almost normal. Crisis averted, then.

Once he'd gotten enough of his strength back to move, he stood up and stopped the IV drip into Sam's arm, leaving the port in just in case he needed more fluids the next day, and removed the one he'd used to give the blood through. There was an ugly purple bruise circling about an inch in diameter around the puncture, meaning some of his blood had probably gone in too fast and seeped out of the vein, but most of it appeared to have done its job. That was good, because Dean was running a little low on spare blood at the moment. If Sam needed any more of it after this, he was gonna have to make it himself.

Realizing how much his hands were starting to shake now, Dean dragged himself over to the fridge in their tiny motel room, forcing himself to drink about half a bottle of Gatorade and eat one of two club sandwiches and some crackers they'd bought at a gas station on the way up here. It didn't help a ton, but it did at least make his hands shake a little less and the building queasiness he'd been battling for the last four or five fills of the syringe disappear.

By now Dean was totally exhausted, emotionally as well as physically, but before he let himself fall into bed he had to make sure Sam was really going to be okay. He sat on his brother's bed again and gently shook him by the shoulder, sighing in relief when Sam groaned and then slowly blinked his eyes open.

"D'n?" he mumbled, words still slurred but from sleepiness now, not delirium. "What… happened? D'you take me to the hospital? I don't remember…"

"Nah, no hospital, not with where those cuts are. You think I wanna get you committed?"

Sam nodded, quickly understanding his brother's reasoning, and examined the bandages on his wrists and the IV port in his right arm.

"You gave me fluids, looks like."

"Yeah, you needed 'em. Speaking of which, here." He produced another bottle of Gatorade, opening it and staring Sam down until he'd drunk enough to satisfy him.

"Okay, so you gave me fluids and…" Sam continued and then stopped, squinting in puzzlement at the circular bruise on the inside of his other arm. "What is this?"

Dean grimaced and held up the now clean syringe he'd used earlier. "You were running pretty low on blood after those ghouls tried to drink it all, so I just… y'know, topped you off." He shrugged at the incredulous look Sam gave him, trying not to make it a bigger deal than it was. "It's not like I haven't done it before, you know."

"Yeah, I know, I just…" Sam ducked his head, and Dean tilted his to one side, unknowingly mimicking the way that weird trenchcoat-wearing angel looked whenever he was confused. "I didn't think you'd want to do that for me right now, after all that's gone down between us recently. Figured you'd just let the ER handle it."

That hit Dean like a punch to the face. Not only had Sam almost bled out because Dean had been brooding too much to pay attention to it, now he was surprised that his older brother had even bothered to save him. As if after all this time, after spending his whole life looking after his little brother and even selling his damn soul for him, Sam still thought that a couple of fights and some tension between them could ever make Dean stop caring about him. And the worst part, Dean knew, was that if Sam really thought that about him, it was only because he'd failed him so completely that it had made Sam doubt his own family's love for him.

"Sam, no, that's not how it is at all!" Dean almost shouted, desperate for Sam to hear him, to understand. "I know we haven't been seeing eye to eye all the time lately, but man, you've gotta know I'll always have your back no matter what. I'm your brother, Sammy. Even if I'm pissed as hell at you at the time, you can still always count on me to help you when you need it. But it works two ways. If I'm gonna look out for you, you gotta tell me when you're in trouble. No more hiding wounds or keeping secrets until it gets almost too bad to fix. Okay?"

"Yeah. Okay," Sam whispered.

"Good. 'Cause Mom, Dad, Adam, they're all gone. You and me are all we've got now, and I don't want either of us going before our time, ever again."

"Me either," Sam said softly, yawning widely before he could stop it. Dean noticed, though, and grinned teasingly at him.

"Better get your beauty rest, Samantha. You're gonna need it when you're scrubbing blood off my upholstery tomorrow."

Sam smiled, laying down and yawning again as his eyes started to drift shut of their own accord. "Jerk."

Dean laughed, flopping down onto his own bed and waiting until Sam had fallen asleep before muttering, "Bitch."