Some characters have it rough, especially those that get infected with a Viral Transformation that gives them a Horror Hunger for human. They may be forced to feed on humans more than they'd like, even becoming good at it, much to their own shame. Or they may try to be a Vampire Refugee or Friendly Neighborhood Vampire, werewolf, or whatever, and only feed on non-sentient things.
Then they make a Muggle friend, maybe even with Love Interest potential! This is all sorts of awesome since it helps reconnect them to humanity and makes their existence bearable, maybe even allowing a semblance of a normal life/relationship.
There is, however, the obvious problem that they are now underfeeding and spending a lot of time with someone who is directly below them on the food chain. Things will only get worse before something goes Horribly Wrong. What usually happens is they suffer a brief bout of Glamour Failure when the Horror Hunger is strongest, they'll reflexively extend their fangs and claws, start seeing in Vein-o-Vision, or put on their Game Face. However they'll manage to retract them through sheer willpower before their new friend/love interest notices... most of the time.
Where they usually fail to maintain the Masquerade is when facing a situation where their new friend is bleeding and they're desperately hungry, and to avoid attacking their friend they give in to the lesser urge for the spilled blood and start lapping it up. Or to have their friend show them a cross/garlic/open flame and for them to recoil in horror before hissing and fleeing (when not spontaneously combusting). At that point, the jig is up and they usually stay away in shame at being exposed or for fear of losing control completely.
On the bright side, the friend does usually prove to be very loyal and finds them afterwards, and decides to take their chances by remaining close.
- Vampire Hunter D: Bloodlust - on the part of Meier Link, the vampire that kidnapped the girl everybody is out to rescue. Throughout the chase we see him resisting his urges to bite her. He doesn't fail, surprisingly.
- Also happened in the original Vampire Hunter D. One time when D was with Doris Rumm, his fangs extended and he had to fight to control himself. Seizure warning, lots of flashing: watch it here, starting at about 55:08.
- Following his transformation into a Half-Human Hybrid, Kaneki from Tokyo Ghoul finds himself standing in a crowded crosswalk surrounded by ordinary humans. As his Horror Hunger begins to overwhelm him, he finds himself going from thinking of those around him as "man, woman, and child" to simply "meat" while biting into his hand and drooling. He's terrified when he realizes what he'd been thinking, and flees the area. On another occasion, after using his powers for the first time, he hallucinates Hide arranged on a beautiful platter and nearly attacks him. This event leads him to slowly begin pulling away from his childhood friend, equally frightened of being discovered or hurting him.
- While critically wounded and starving, Nishiki attacks his human girlfriend and reveals himself as a Ghoul. Her willingness to accept him brings him back to his senses, and prevents him from killing her.
- This is essentially the entire premise of the fanfiction story For Love Or Blood... the trope, however, is subverted in that Jericho, the protagonist, isn't able to restrain his Horror Hunger when his first Love Interest is injured, and ends up killing her. Angst ensues.
- In The Return Misako (part of a brood of Friendly Neighbourhood Succubae) has to be reminded several times not to refer to her extended human family (and humans in general) as "meatbags".
- There are several My Little Pony: Friendship is Magic fanfics that involve a member of the cast transformed into a changeling. Nearly all of them use this trope at some point. (changelings feed on love rather than blood, but they can stimulate their target with mind control powers)
- There is at least one MLP: FIM fic that has actual vampires and features this trope, such as My Roommate Is A Vampire where the vampire in question (DJ Pon-3) states the trope's name verbatim.
- Fan art gave this treatment to poor Twilight after she nearly eats a burger in Equestria Girls. They took the idea of her actually eating meat, liking it, realizing what it is, then returning home to find herself surrounded by tasty (but now sentient) cows, pigs, and ponies.
- Occurs in this fic for A Monster in Paris.
- Early in the Interview with the Vampire adaptation, Louis feels tremendous shame and guilt over feeding on people, so he resorts to consuming the chickens he owns and any rats he comes across. Needless to say, this is portrayed as being be like malnutrition at best or semi-starvation at worst to a normal person. Ironically, this means that anyone close to Louis is in tremendous danger of his bloodlust without him intending or realizing it.
- Let the Right One In has this happen towards the middle. Eli follows Oskar to a secluded spot after she hasn't fed for a few days, and Oskar unexpectedly cuts his palm and offers to be blood brothers with her. She manages to fight the urge to eat him by lapping up the blood he was spilling, but reveals her Game Face in the process, growls, and runs away.
- Happened in the first Madagascar when Alex realized all his friends were, in the wild, basically his food. Cue Meat-O-Vision.
- Freddy in The Return of the Living Dead, anguished by the pain of decomposition, loses it and attacks his girlfriend Tina, desperate to eat her brain. His Expy succeeds in the sequel, in a snarky Take That! parody of Kiss of the Vampire.
- Treated semi-humorously in Shadow of the Vampire, where Count Orlock appears as Max Shreck, an actor impersonating a vampire, and Murnau has to prevent him from preying on the staff and co-stars at almost every turn.
- Twilight, big time.
- Parodied in Vampires Suck, when the main character cuts her finger and one of the vampires actually sees her head transform into a Big Mac.
- What We Do in the Shadows: After being transformed into a vampire, Nick states he's very, very tempted to eat his Human friend Stu. But he won't, even though he does smell delicious. Because they're best mates, and best mates don't eat each other. All while Stu is sitting right beside him.
- In Life Blood, Brooke is so completely overwhelmed by the scent of Bill, the first human she encounters after being resurrected as a vampire, that she bites him and kills him despite Rhea's attempts to stop her.
- This is the entire plot of Twilight. This is lampshaded in the How It Should Have Ended entry for Twilight.
Alice: Edward, it's like you're a recovering drug addict, that's dating crack. It's never gonna work.
- Happens to Ivy multiple times when around Rachel in the early books in The Hollows series.
- Nat from Nathaniel Keene feels like this quite often after being turned into a vampire:
"There were other changes which made him uneasy. He could hear people: hearts pulsing out steady rhythms, ripe for the picking like some sort of twisted fruit orchard. And he could smell them too - could dig beyond layers of perfume and sweat to catch the rich, warm, nauseatingly delectable scent of human. A scent which, he grudgingly had to admit, was infinitely more appetizing than that of the cold, packaged blood he was forced to subsist on."
- Alluded to for Angua in Feet of Clay, although she seems to have her werewolf instincts well under control, and conceals them from Cheery more because she's afraid the truth will harm their budding friendship than for fear she'll actually hurt the Watch's new recruit. Angua herself admits that it's not a matter of not wanting to [eat people], it's a matter of wanting to and not doing it.
- Played for laughs in The Truth: Otto Chriek is a "Black Ribboner" (member of an organisation of reformed vampires) and a woman faints in front of him. The image of a fainting woman with "bosoms going in and out and up and down like that" triggers the vampiric urges and he panics, and ends up singing jolly songs about not wanting to drink blood ("zer drink zat's in zer livink vein is not zer drink for me ...") until someone provides him with non-human blood.
- The Star Trek: The Original Series novel First Frontier featured the Clan Ru as enemies. Essentially, they're sapient velociraptors (the cinematic version). They find it nearly impossible to live in peace with the humanoid mammals and quasi-mammals that dominate the galaxy for this reason. (And prompt Kirk to wonder how seriously he'd be able to take people who smelled like warm baking bread.)
- Taxxon morphs in Animorphs are like this. It turns out the actual Taxxons aren't any happier about it, and many of them use morphing technology to mode lock themselves in other forms post-war.
Elfangor: You're going to have to fight the hunger.
Arbron: What, are you afraid I'll morph and try to eat you?
Elfangor: Yes, Arbron. I am afraid.
- The Dresden Files: This becomes a major problem for Susan Rodriguez after being "half-turned" by the Red Court. She initially goes into hiding, then gets help from an organization of other half-turned vampires, but it's made clear in her later appearances that she's only barely keeping herself under control whenever she's around normal people. This doesn't seem to be a problem for Martin, the other major half-turned we see, but he's much older than Susan and intentionally bland anyways.
- Thomas Raith also suffers from this during his stint as a Friendly Neighborhood Vampire. While he is able to feed often, first through one-night-stands with various women and then by opening a hair salon (it makes sense in context), he's only "nibbling" and not truly satiating his Hunger. His willpower gives out after being tortured during Turn Coat, and he goes back to feeding as much as he likes on human "cattle" like the rest of the Raiths.
- Thirsty, as the protagonist turns into a vampire.
- The first phase of being transformed into a vampire in the Night Huntress books is a horrific uncontrollable surge of the normal blood thirst present in all vampires. Most vampires manage to get back normal control after around a week in restraints being fed on bagged blood and attended by undead. Tate managed to get to the point where living people were allowed into the room after about a day.
- In Diario de un Zombi, Erico is a zombie trying to ferry two living humans to the alps. The flesh-eating pangs slowly grow over time, adding him to the threats they face.
- Not normally an issue for Jack from The Vampire Files, as his usual appetite for blood isn't that intense. If badly wounded and a few quarts low himself, however, he starts smelling the blood under peoples' skin and has to really strain to hold back his body's desperate survival-drive to feed.
- Darren Shan, the Vampires take a logical approach and minimize the chances of being caught or unnecessarily harming humans, including using blood-packs, and consider it honorable to keep humans alive. After all, they are a handy food source. In contrast, the 'Vampaneze' tend to go into a feeding frenzy with very unpleasant results.
- Rev Bem in Andromeda is always having to stop himself eating and laying his young inside his crewmates. He relies on his religion ("Wayism") to get him through the day. Apparently, Magog physiology requires that he kill something to activate his digestive system. He keeps a supply of live fish aboard the ship for that purpose.
- Mitchell in Being Human had to do this practically every other episode, with mixed results.
- Angel sometimes has this problem in Buffy the Vampire Slayer and later in his own series. He's mostly overcome the issue by using animal blood, but flashbacks to his early attempts at living around people show it wasn't always so easy for him to resist humans, and if he's severely weakened or starved, he's liable to grab and start drinking from someone before he even realizes what he's doing.
- Other vampires in the Buffyverse have the same problem, though being soulless demons means that they usually don't even try to restrain themselves. One exception is Harmony, who joined the good guys in season 5 of Angel and, of course, wasn't allowed to feed on humans. She complained that, since she doesn't have a soul like Angel, it's twice as hard for her to resist eating people.
- In the second season, Spike even lampshades this by stating outright that one of the reasons he doesn't want to destroy the world is "Billions of people walking around like Happy Meals with legs." He also doesn't like how Angel is stealing Drusilla, but that's beside the point.
- M'lee, the calcium-eating alien in season 1 of Farscape did this, having the light-emitting horn crown on her head change color when hungry for calcium. Interestingly, she managed to "fang off" after her cover was blown to plead with Crichton that she isn't evil, but she needs calcium to live and (being trapped on a forest asteroid with no other animals) has to find a humanoid source to eat. Happily, she isn't killed and they manage to find her a suitable substitute to eating the main cast... the other villain of the week and the Peacekeepers arriving to investigate. It's implied that she's now being employed by Scorpius in exchange for the disloyal members of his crew.
- M'Lee's plotline was apparently going to come to some sort of larger fruition later on, had the series continued. Sadly...
- Lyekka of Lexx was very matter-of-fact about this: she'd "prefer" not to eat her human friends, but deprived of other food sources, she would. It was less of a problem than in most stories, since the main characters are all completely indifferent to the deaths of humans who aren't them.
- An odd, non-predatory and character-specific example comes in Terminator: The Sarah Connor Chronicles, where Cameron admits to John Connor that, deep down, her hard-wired programming is permanently directing her to kill him at all times, and is overridden only by the other programming that the future John Connor used on her. At one point, Cameron does revert and starts trying to kill John, only to override her own termination directives at the last second. Cameron also has to fight the opposite reaction when dealing with people she interprets as threats to John, and also admits that she doesn't know whether she will kill someone who she views as a threat. Her uncertainty regarding both of these eventually drives her to wire up an explosive device into her skull in case she loses control and needs to be put down.
- A variation in Smallville season eight. The sole purpose of Doomsday is to destroy Clark, but the monster would also gladly massacre scores of humans whenever he is free. The human host, Davis Bloome,has no recollection of the rampages. However, Brainiac also programmed into him an attraction to Clark's Platonic Life Partner, Chloe Sullivan, making his blackouts more and more frequent. Suicide failed to end his tormented existence, and Davis was forced to kill people in his human for to suppress the bloodlust. Then he discovered Chloe's presence makes him human, but that also eventually fails and he kills her. Good thing the Reset Button was handy, but in the end there was a Downer Ending.
- Oddly simultaneously inverted and played straight. Sam is a demon blood-tainted human who became addicted to demon blood and the demon-exorcising power that it provides. Withdrawal kind of sucks when your main target as a hunter is demons and your weapon of choice is a knife. And then the demons use this advantage and make him drink their blood. It doesn't turn out well for them.
- Played straight with Lenore and Benny, who both want to go Vegetarian Vampire but struggle with temptation. Lenore commits assisted suicide after she's psychically forced to attack humans. Benny agrees to Dean's plan of killing him so that he can rescue Sam from Purgatory. He promises Dean that he'll come back with Sam, but ends up staying behind to fight off a group of attackers so that Sam can escape (although he was clearly intending to stay there anyway, because he knew the temptation on Earth was too much for him).
- Seen in the pilot for the television adaptation of The Vampire Diaries when the lead vampire is around his bleeding Love Interest.
- Seen again in episode 2.03 when Matt started bleeding and Caroline just couldn't resist taking a bite.
- Stefan is noted as having a problem with blood addiction. His use of animal blood, while most non-homicidal vampires steal from blood banks, is because he's afraid of relapse. Later on he starts to carefully start drinking human blood again, as using only animal blood makes him weaker. In the season 2 finale Klaus makes him drink bag after bag of human blood, until his addiction resurfaces and he turns into a "Ripper", an extremely not Friendly Neighborhood Vampire.
- Episode "Hungry" of The X-Files featured a brain-eating mutant who tried not being a brain-eating mutant.
- On Misfits, Seth finds the power to resurrect the dead and gives it to Curtis to bring back his dead girlfriend. Unfortunately, the resurrection causes her (and anyone she bites) to turn into a zombie. She can hear heartbeats and gets nervous when she's around him because she doesn't want to eat him, so she eats his pet lizard and later his neighbor.
- In Vampire: The Masquerade, younger vampires can feed on animal blood in lieu of human blood, but it's not nearly as satisfying. Unfortunately, that means this trope occasionally comes into play, because every once in a while a neonate attempts to maintain relationships from their mortal lives while also trying not to feed on humans. Sad to say, when this inevitably happens, it is treated as a breach of the Masquerade and the bloodbag in question needs to have their memory erased or be killed before they can spread the word.
- This trope is mechanically enforced in both Masquerade and the successor game Vampire: The Requiem, as a vampire low on blood will often have their body taken over by the Beast, who doesn't care where the blood comes from as long as it gets fed.
- Requiem vampires have it worse, mechanically, especially in 2nd edition: vampires in Masquerade can at least try to feed on animal or medically stored blood. Requiem vampires can only feed on animal blood at the lowest tiers of power, get effectively nothing from medically preserved blood, and can't any sustenance from corpse blood at all.
- The Achilles' Heel of Vampire teams in Blood Bowl: Vampires have a 1/6 chance each turn to run off to seek blood to feed on instead of playing the game. This leads to them either draining one of your Thrall players (leading to an instant KO) or running off the pitch to hunt audience members (cancelling the action and causing a turnover).
- Arcueid in Tsukihime. Normally she's able to suppress her bloodlust by sheer power, but when events in the story force her to use much of it up, she's left relying mostly on willpower. Despite knowing this, protagonist Shiki Tohno chooses to stick with her. Satsuki is another example for whom things didn't end as well.
- Digital Devil Saga. Every enemy, potentially, can be easily devoured. Mick the Slug is quite fond of eating his own men.
- In Soul Reaver you can choose to live peacefully inside the Human Citadel. To survive, Raziel can take small sips of energy from the friendly locals (if you haven't killed off their fellow vampire hunters or neighbors, that is). Be a glutton though and the host dies.
- Duane in Unsounded is a "plod" who has managed to retain his sentience and sanity...in the daytime. At night, he's a plain old zombie and needs a partner with a magical trinket to keep him pacified; and at all times he has a nigh-insatiable hunger. It's not hard to guess what he hungers for, but it isn't explicitly shown until the end of chapter 6, when he loses control and messily slaughters a member of Starfish's troupe, then spends the rest of the night nibbling on his remains.
- Daniel basically wants to drink the blood of any human being that's close to him.
- In one of the Mina and The Count shorts, the Count is invited to dinner at Mina's house. He's very disturbed when he discovers Mina has an older sister Lucy (Mina never mentioned her because she doesn't like Lucy). The Count's favorite prey (for blood drinking) are young women. Sitting through dinner is a bit awkward for the Count.
- My Little Pony: Friendship is Magic has a variation with the changeling Thorax from "The Times They Are A Changeling". He doesn't desire to harm anyone, in fact he wants genuine friendships to substitute his need to drain love. Unfortunately, strong amounts of love trigger his instincts and cause him to hiss ravenously against his will and Flurry Heart's Crystalling has filled the Empire with it. It doesn't help he admits he's starving. It pays off eventually.