Title: Elena Gilbert
Content:  Executive producers Julie Plec and Kevin Williamson agreed that in the book series, Elena was turned into a vampire too early, which was around page 200 of The Awakening. Elena's transition into a vampire was planned for two years. Plec said: "That felt obviously too soon, and rushed, and we didn’t want to make a show about a teenage girl who instantly becomes a vampire. But we always knew that her journey would take her there eventually". At the second season's conclusion, Elena was nearly turned into a vampire. Dobrev was happy that she wasn't, because she felt "it would have been too soon", and also didn't think it was something Elena or she wanted. In the show's third season, Elena has a brain hemorrhage which was initially 
Title: Elena Gilbert
Content:  of Elena's story revolves around her relationships with vampires Stefan Salvatore and his older brother, Damon. It is revealed that Elena is a Petrova Doppelgänger, which is thus responsible for her being identical to her ancestor, Katherine Pierce (née Katerina Petrova). This also has the implication of making her a supernatural creature. Dobrev portrayed the "conniving" Katherine as well, who is opposite of Elena. The actress stated that it has been a challenge distinguishing the two, and enjoys playing them both. In the television series's fourth season, Elena becomes a vampire and dies then deals with the struggles that come with her change. She took the cure and became human again towards the end of the sixth season. 
Title: Elena Gilbert
Content:  to be a concussion, and begins to die. In what was described by the International Business Times as "the moment Vampire Diaries fans have been waiting for", Elena had to choose whether to be driven to Damon or Stefan to say goodbye to. At the time, Klaus was killed, meaning all vampires sprouting from his bloodline also die, which includes Damon and Stefan. She picks to say goodbye to Stefan. However, all these vampires end up surviving when Klaus never really dies. To save her, Doctor Meredith Fell (Torrey DeVitto) fed Elena Damon's blood. Rebekah Mikaelson kills Elena on Wickery Bridge, unaware of the vampire blood in her system. She woke up as a vampire at the end of the season. The Hollywood Reporter interviewed Plec, and 
Title: Elena Gilbert
Content:  Before The Vampire Diaries, Elena dated Matt Donovan (Zach Roerig), who was unable to move past his feelings for her initially after their break-up. Elena began dating Stefan Salvatore (Paul Wesley), and later discovered he was a vampire. As the episodes progressed, she developed a connection with Stefan's adventurous brother Damon Salvatore (Ian Somerhalder), who consumes human blood, unlike Stefan, who has an animal blood diet. Speaking about the different qualities Stefan and Damon bring to Elena, Dobrev said they have "different qualities that are very appealing", which combined make "the perfect man". She said "Stefan is committed and sweet and protective and loving, and Damon is spontaneous and crazy and fun and exciting".  After Elena became a vampire, she became sired to Damon and they slept together. According to Plec during an 
Title: The Vampire Diaries
Content: Nina Dobrev as Elena Gilbert (season 1–6; guest season 8), a young orphan who falls in love with vampire Stefan Salvatore and later his brother, Damon, creating a love triangle. When Stefan shuts his humanity off after being blackmailed by Klaus, Damon is given the opportunity to grow closer to Elena. This results in her being further drawn into the supernatural world and results in her struggling to survive supernatural events in the town. Dobrev also portrays Elena's doppelgänger, Katerina Petrova also known as Katherine Pierce. Dobrev sporadically appeared in subsequent seasons and played a significant role in the fifth season. Dobrev also 
Title: Elena Gilbert
Content:  In season three, Elena does everything in her power to make Stefan get his humanity back, which was turned off by Klaus as payment for saving Damon from a werewolf bite in the latter part of season two. Meanwhile, she grows closer to Damon while working together on saving Stefan and trying to defeat Klaus, eventually even sharing a kiss. She later admits to Stefan that she has feelings for Damon as well but that she never stopped loving Stefan. While in Denver together, Elena kisses, Damon, later telling him that she doesn't know how she feels about him. It is eventually revealed that Elena met Damon the night of her parent's death, though he compelled her to forget. She eventually chooses Stefan in the season finale but before she can tell him, Elena drowns while having vampire blood in her system. During the last moments of season three, she awakens as a vampire in transition.
Title: Stefan Salvatore
Content:  In the season four premiere, Stefan tries to get Bonnie to save her from becoming a full vampire, however, she along with several other vampires are captured by the Founder's Council. As Elena begins to die and out of desperation to keep Elena alive, Stefan kills a guard and uses his blood to allow Elena to feed and to complete her transition into a vampire. Stefan gives Elena a daylight ring, which was made by Bonnie, in order to protect Elena from the sun. Stefan tries to assure Elena that everything will be okay and that they'll take Elena's newborn vampirism one day at a time. During the second episode of season 4, 
Title: The Departed (The Vampire Diaries)
Content:  The episode marks a pivotal point in the series; where Elena begins transition marks a change in the series' dynamic. The plot to turn Elena had been in the works since the series began, where executive producers Kevin Williamson and Julie Plec had signed on to the project and agreed that at some point, she would be turned. Initially, this plot was to be used by the end of the second season.
Title: While You Were Sleeping (The Vampire Diaries)
Content:  Elena (Nina Dobrev) wakes up in her body after three weeks since the day Katherine has taken over it and, she is trapped at the college dorms. Stefan (Paul Wesley), Bonnie (Kat Graham) and Caroline (Candice Accola) asked Liv (Penelope Mitchell) to cast a spell and seal her there since they can find out the antidote of the ripper/werewolf virus that Katherine injected her body with before she died. Stefan is there with her while Bonnie is with Liv trying to teach her how to practice magic and Caroline is at Wes' laboratory trying to find the antidote. Meanwhile, Damon (Ian Somerhalder) is 
Title: Elena Gilbert
Content:  her transition as "monumental changes" which would have Elena in for a "wild ride". Plec said Elena becoming a vampire is "an awakening of a person who is about to go through a lot of changes", and "she is going to evolve as a person and her relationships are going to evolve accordingly". While Stefan was afraid she would hurt someone, Damon thought it was inevitable and wanted to "rip the band-aid off". Plec felt that "She’s, unfortunately, not getting the same advice from the two people she values most in the world. It’s going to make it more difficult for her", while describing the situation as "a whole new Elena and it’s a whole new day. It’s a different dynamic between the three of them especially".

Question: when does elena turn into a vampire in the tv series?
Answer: season four.
fourth season.