Nausea
Nausea or queasiness was a stomach condition in which the individual felt like they needed to vomit. Sometimes this was associated with motion sickness, pregnancy, (see morning sickness) () pressure changes, or excessive g-forces.

In 2153, Dr. Fer'at, a psychiatric analyst posing as a pathologist, examined Captain Jonathan Archer for signs of pyritic radiation. Fer'at asked Archer if he had experienced symptoms of nausea or dizziness. ()

Dr. Phlox prepared anti-nausea medication for Charles Tucker III and Hoshi Sato after Sato vomited in the decontamination chamber's toilet on . ()

Lieutenant Malcolm Reed experienced nausea during the  mission to Mars in 2155. Doctor Phlox gave him an organic waste bag, which he used. ()

When asked by Hikaru Sulu what he thought of how they were changing course so much, Ensign Pavel Chekov replied, "I think I'm getting space sick." ()

After Spock was shot by a poison flower and being injected with medicine, Kirk asked, "Spock, are you all right?" to which Spock replied, "Dr. McCoy's potion is acting like all his potions, turning my stomach. Other then that, I am quite well." McCoy then said to Spock, "If your blood were red instead of green, you wouldn't have an upset stomach." ()

In 2370, when asked by Arjin how she felt when she learned that her field docent was going to be Curzon Dax, Jadzia Dax believed nauseous to be the most accurate word. ()

Nausea could be a side effect of a vaccine. Julian Bashir once gave Kira Nerys a vaccine which he warned would cause mild nausea. ()

Nausea could be caused by the emotion disgust. When Jake Sisko heard a surgeon make a joke about his food and surgery, he felt nauseous and ran out of the room, thinking he was going to vomit. However, he did not. ()

When Kira was feeling guilty about not protesting when the Cardassians took over Deep Space 9, she claimed to feel nauseated whenever she looked in the mirror. ()

When Dukat was deceiving Benjamin Sisko into thinking the latter was injured, he lied that Sisko had suffered a "bout of nausea" and vomited in his sleep. ()

In 2371, Ensign Harry Kim and several other officers on board the  complained of dizziness and nausea while the ship was near a type 4 quantum singularity. ()

When the Vidiians extracted the Klingon DNA from B'Elanna Torres, she became fully Human. She described this as feeling so weak and sick to her stomach. ()

During The Doctor's delusions on Voyagers holodeck, he asked a holographic Captain Kathryn Janeway if she were experiencing any pain, dizziness, or nausea following a supposed Kazon attack, to which she replied that she had a headache and felt disoriented. ()

In 2372, after being telepathically burned by Kes, Lieutenant Tuvok was told by The Doctor to return to sickbay if he experienced any symptoms of nausea or dizziness. ()

Worf had a very weak stomach when it came to zero gravity, becoming ill while attempting zero-gravity combat training at Starfleet Academy. ()

Fluctuations in gravity were known to cause nausea in humanoids. ()

In 2371, Benjamin Sisko built a gravity net into his replica Bajoran lightship because historically-accurate weightlessness would make him queasy. ()

Ezri Dax was known to suffer from space sickness, a condition which could cause nausea, after being joined with the . ()

B'Elanna Torres felt nauseated after Voyager was infected by a macrovirus in 2373. Tom Paris was surprised by this since Klingons possessed a redundant stomach. ()

Sometime afterwards, the Changeling impersonating Dr.  advised Captain Benjamin Sisko to report any symptoms of nausea or dizziness to him after he was caught in an explosion while operating a holosuite console. ()

In 2375, The Doctor told Neelix that nausea was one of the symptoms of nihiliphobia, a condition from which Neelix was suffering while Voyager was trapped in . ()

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Medical conditions