In this trope, when a character feels tired, it's never just Sleep Deprivation or a minor illness like a cold. Nope, it's a very serious condition. At best, it's something that's very drastic but ultimately survivable, such as appendicitis. At worst, it means their days are numbered. In sci-fi and fantasy works, it might mean something otherworldly such as alien mind control or Demonic Possession.
Seeing as many conditions do make you tired, especially infections since your body is using energy to fight the bug, this trope isn't just "sick character feels tired". In order for it to be this trope:
- It has to be serious. Diseases less serious than the flu do not qualify for this trope.
- It has to be either the first sign (or one of the first signs) that things are amiss, or a sign that the condition is serious. In the first case, the character might start off just a little sleepy and the characters brush it off as sleep deprivation before the other symptoms come on. In the second case, the character might already be established as sick, but if they start to become lethargic, that's seen as them taking a turn for the worse or being more likely to die.
There might also be a danger that if the character falls asleep, they will die, so the other characters try to keep them awake. This trope can be a source of Paranoia Fuel, as tiredness is such a common symptom, and it's also easy to imagine.
Contrast Victorian Novel Disease, for when a woman has a terminal disease but she's just as active (and pretty) as ever. Can overlap with O.O.C. Is Serious Business if the character is normally energetic and Fell Asleep Driving if they're driving as well. Not to be confused with Never Sleep Again and Slain in Their Sleep, for when people are killed in their sleep by outside forces. Can lead to Passed in Their Sleep. If the person is already dead and is mistaken for sleeping, that's Please Wake Up.
- I'm Standing on a Million Lives: The party split up to complete their last objective for their current mission: to explore a certain percentage of the map. Expecting it to be easy, they each take leisurely strolls in opposite directions, until a sudden freak blizzard strikes. Not only does this make it extremely difficult to keep uncovering the map, but the cold temperatures start making them slowly freeze to death. Each of them tries their best to keep moving and stay awake, knowing that if they fall asleep that not only will they die, but they won't be able to Auto-Revive while their body is frozen.
- In the Big Finish Doctor Who episode "Protect And Survive," Ace and Hex find themselves in an alternate history where the Cold War ended in a nuclear apocalypse, and barely have enough time to seek shelter with the elderly Marsdens before the nearby RAF base is nuked. It soon becomes clear that they've suffered a Fallout Shelter Fail and all of them have absorbed a lethal dose of radiation: consequently, when Albert and Peggy Marsden's initial symptoms (a Headache of Doom and Blood from the Mouth) escalate to crippling fatigue and longer periods of sleep, it's a good indication that they don't have long to live. Sure enough, the next scene features Ace and Hex hauling Albert's corpse out of the shelter. However, it turns out that all four of them are trapped in a "Groundhog Day" Loop, and the Marsdens are alive again — and forced to go through the apocalypse all over again, on each occasion dying in their sleep due to radiation exposure.
- In Phase IV of Zenith, Dr Michael Peyne is cursed with an accelerating case of Merlin Sickness by the victorious Lloigor, and though he initially feels energized by his newfound youth, his Apocalyptic Log soon mentions how tired he's started to feel as he re-enters his childhood. Eventually reduced to scrawling badly-spelled notes in a barely-legible scrawl, a very young Peyne admits that he's too tired to write anymore and needs to lie down. When Ruby finally arrives to say goodbye, he's little more than a baby sleeping under his adult-sized shirt, and soon succumbs to Death by De-aging.
- In the Rugrats prequel fanfic The Joys and Sorrows of Young Charles Finster, the chapter "The Appendix" has Charles feeling tired. He initially thinks he's just worn out from the exercises his father Marvin is having him do, but then he gets a severe stomachache and his condition is revealed to be appendicitis.
- In Ponyo on the Cliff by the Sea, near the end of the film, the first thing that happens when Ponyo loses her magic is that she becomes more drowsy than usual and becomes unable to make another candle grow for Sosuke and his boat.
- Up: In the beginning, Ellie is too weary to climb the hill for her and Carl's picnic. The next scene has her in the hospital, and in the scene after that, she's dead.
- Backdraft: Stephen "Bull" McCaffrey says, "I feel so tired" as his last words.
- "I'm tired" serves as Annie's dying words in Imitation of Life (1959).
- In Return of the Jedi, when Yoda is on his deathbed, he's very lethargic and talks about wanting to sleep.
- In the days following the nuclear attack on Sheffield in Threads, Ruth's grandmother — already badly affected by the shock — begins sleeping through mealtimes, and though Mr and Mrs Beckett believe that rest will do her some good, it's obvious that she's ailing. The very next scene with Becketts features her body being hauled out of the fallout shelter by her grieving relatives.
- Books of the Raksura: Flower's constant fatigue in The Serpent Sea is one sign that she's near death from old age.
- In Charlotte's Web, the eponymous spider becomes listless towards the end, claiming to be too tired to sing Wilbur to sleep. At the very end of the book, she dies.
- Discussed and zigzagged in Flora And Ulysses: Flora's mother says she needs a nap despite usually being an "anti-napper"; someone who regards naps as a waste of time. Flora wonders if this means her mother is possessed, but she isn't. She is, however, in shock, but the shock goes away when she wakes up.
- In The Memoirs of Twaddler by Andrey Desnitsky, a Follow the Leader novel heavily inspired by The Screwtape Letters, Nadezhda being unusually exhausted is the first sign of her having cancer, which leads to her death a few months later.
- In the Mog book "Goodbye Mog", Mog is "dead tired" on the first page, takes a nap, and dies in her sleep. She does get an Unexplained Recovery in the next book, though.
- In The Secrets of the Immortal Nicholas Flamel, Prometheus says: "I'm tired now, so tired. It will be good to rest." He then proceeds to die in the arms of his daughter. Bonus points because the aforementioned daughter had just revived him, but he made her let him die.
- So I'm a Spider, So What?: Kumoko gets half of her body bitten off while battling a swarm of monstrous apes. As her HP starts dropping, she feels drowsy and is tempted to fall asleep, but fights it off because she knows that if she does, she'll die.
- Early in the fourth season of Farscape, Crichton is forced to stay aboard Elack, an extremely elderly Leviathan living out the remaining weeks of his life in the Sacred Space. As Pilots share the lifespans of the Leviathans they've been bonded to, Elack's Pilot has also grown old and spends a lot of her time nodding off; initially a simple case of Senior Sleep-Cycle, as Elack draws closer to death, she begins lapsing deeper and deeper into unconsciousness until it's almost impossible to wake her. In the end, she and Elack are able to marshal enough strength to perform a Heroic Sacrifice and save the main characters.
- House: In "Fidelity", a woman is admitted with symptoms of African Sleeping Sickness, with the wrinkle that neither she nor her husband has been to Africa. Her symptoms get worse, resulting in a coma.
House: She's sleeping eighteen hours a day, it takes a team of doctors and a coma to realise she's got sleeping sickness?
- Star Trek: Deep Space Nine: In "Babel", O'Brien feels tired. He thinks he's just worn out from all the chores he's been doing, but it turns out that he's coming down with a virus called the "aphasia virus", which spreads to the rest of the crew and would have killed them if not for the work of Dr. Bashir and others.
- Star Trek: Enterprise:
- In "Fight or Flight?", when Hoshi's pet slug Sluggo doesn't move much, this causes her and Phlox to suspect that it's dying.
- In one episode, Trip and Archer are in a Thirsty Desert and Trip becomes very sleepy. Archer thinks this is a sign he has heatstroke and needs to stay awake lest he go into a coma.
- Star Trek: The Next Generation:
- In the episode "The Battle", Picard feels tired and he has a headache. It turns out that both symptoms are the result of mind control by some Ferengi, the leader of which wants revenge on Picard for killing his son in a battle years ago (his son had attacked Picard's ship without provocation).
- "The Arsenal of Freedom": After attempting to evade an automated hovering weapons system, Doctor Crusher and Captain Picard both lose their balance over a subterranean opening, and fall into a cavern. Captain Picard only sustains moderate injuries, but Doctor Crusher breaks her leg and cannot move. Furthermore, she keeps drifting in and out of consciousness from the shock, where Picard attempts to keep her awake by keeping her talking.
- During the ending of Persona 3, after the protagonist successfully sealed away Nyx at the cost of all of his life energy, he spends the rest of the school year constantly tired until he finally falls asleep in Aigis' lap. The FES-exclusive campaign "The Answer" reveals the protagonist has died after falling asleep.
- In The Secret World mission "Contagion," Julia Smith appears to have finally relaxed long enough to have a lie-down, understandable given that the Smiths have been on high alert for the last few days. However, it very quickly turns out that Julia's actually been exposed to the Filth at some point since the disaster in the Carpathians began, and the little sleep she's having is more akin to a feverish coma; in the event that she survives the initial infection, she'll end up transformed into another one of the Filthy Swarm wandering the Carpathian caverns. Thankfully, Emma Smith is reportedly able to save her.
- Telepath Tactics, Harynx's death message has mentions of feeling tired, overlapping with I'm Cold... So Cold....
- Averted in Melody when Becca yawns early in the story. It’s not from any illness at all, but from being kept up at night by an annoying dripping faucet. If the protagonist offers to fix it for her, this kicks off her romantic path.
- Doki Doki Literature Club!: Sayori's difficulty waking up in the morning is initially played as just a cute quirk, but it's subtle foreshadowing that she has a health issue. One that is not exactly physical and much, much worse than anyone else realised.
- Homestuck: At the start, Jade keeps falling asleep often at the worst of occasions and though everyone thinks she's narcoleptic, it turns out to be Vriska's doing. Vriska's thing is that she has Mind Control powers, but since Vriska and Jade are two separate species, all she can do to Jade is force her to go to sleep. The reason why Vriska keeps interfering with her like this is to manipulate events on the end of Jade and her friends so that Vriska would have a huge powerful antagonist to fight against and defeat on her end (in a somewhat complicated Stable Time Loop - Vriska knows that, no matter what, that antagonist will exist, so she inserts herself into the story as the one being responsible for its existence).
- In the Arthur episode "So Long, Spanky", the eponymous budgie is seen looking droopy. He dies in the next scene.
- Used in an episode Drawn Together where the pumpkin carriage crashes (Mulan was driving), mortally wounding some of the Disney Princesses. Princess Clara begs Sleeping Beauty to keep her eyes open, only for her to respond with "But... I'm so... tired."
- Madeline: In the adaptation of the first book, Madeline doesn't ice skate with the other girls. Miss Clavel asks her why and she replies that she's tired. Initially, Clavel thinks that Madeline just stayed up late pillow fighting, but it turns out to be appendicitis. This is different from the book, in which the appendicitis came on suddenly.
- In the animated series version of Milly, Molly:
- The episode "Grandpa's Oak Tree" has Grandpa Peg being slow to wake up. Dr. Smiley says that Grandpa is "wearing out" and "may never live to see another winter" and sure enough, he dies in the episode.
- In "Goodbye, Alf", the farmer is immediately worried when he sees his horse Pepper lying down despite it being the middle of the day, and sure enough, she's somehow caught a serious illness. Alf's grandma makes her better though.
- The Simpsons: The main plot of "Dog of Death" is that Santa's Little Helper has a "twisted stomach" and will die if not given surgery. The first sign that he's unwell is when he walks into the living room with a droopy appearance and flops down.
- The Smurfs (1981): In "Squeaky", after Smurfette's mouse Squeaky saves her from a fire, he's seen with a sleepy expression. The next morning, he's dead.
- Subverted in The Transporters episode "William's Scrap Yard Nightmare". William the sentient boat feels tired and thinks he must be broken beyond repair and "ready for the scrap yard". As it turns out though, he is broken (namely he has a broken cog) but he can be repaired.
- When a cat is dying of old age, they'll often sleep more.
- Roald Dahl had a daughter named Olivia, who unfortunately died as a kid due to measles complications. Her last words were "I've gone all sleepy."
- Sleeping sickness is a disease caused by the parasitic protozoan Trypanosoma brucei. In the hemolymphatic phase, the patient suffers from mild weakness and fatigue; but once the infection progresses to its neurological phase, it disrupts the victim's sleep-wake cycle, causing episodes of extreme somnolence during the day. Due to the former phase's vague symptoms, a conclusive diagnosis is usually only attained during the disease's second stage, which is fatal if not treated.
- One of the first signs of a concussion is feeling sleepy. Contrary to popular belief, falling asleep will not cause a person to slip into a coma. However, sleep itself can mask the symptoms of serious brain damage, so it's important for somebody to check on them regularly to make sure they can be roused normally and aren't having worsening symptoms.
- Sometimes if a person is dying of old age, their Senior Sleep-Cycle gets worse and they become bedridden.
- Moderate to Severe Hypothermia can cause drowsiness, leading to unconsciousness, and if they are not removed from the cause of hypothermia, death in short order.
- Severe to Life-Threatening blood loss can cause drowsiness, as the body either struggles, or is no longer able to supply enough blood to the brain to maintain consciousness.
- One of the symptoms of poisoning by depressants (substances that dampen the activity of the nervous system, like alcohol, or opioids), or tranquilisers is drowsiness, and in lethal cases, would be followed by said person no longer breathing, as the breathing response is also affected.
- Although the drowsiness is not the direct cause of death in this instance, someone who is no longer responsive after poisoning would not be able to inform you about what substance caused it, or the amount they took, making it harder to find an antidote, or ensure that they are still alive.