Regeneration

The Doctor regenerates into his sixth incarnation. (DW: The Caves of Androzani)

The Doctor regenerates into his tenth incarnation. (DW: The Parting of the Ways)

This article is about the Time Lord physiological process. For the non-fiction book see Doctor Who: Regeneration

Regeneration is the process by which the Time Lords (and a few other life-forms) could renew themselves physically by changing themselves if worn out by age or has suffered some life-threatening injury or infection or even at will.

Regenerations in General

The Process

Appearance

During the Master's regeneration, the Time Lord seemed to shed excess energy from his wrists. The energy appeared to fall to the floor of the TARDIS.

During a regeneration, the body often shines with milky white light also known as bio-energy (DW: Logopolis, Time and the Rani, Doctor Who: The TV Movie) or with a violent-seeming great discharge and torrent of golden bio-energy. (DW: The Parting of the Ways, Utopia, The Stolen Earth) In other cases, there was no visible energy discharge. (DW: Planet of the Spiders, Destiny of the Daleks)

Just prior to his ninth regeneration, the Doctor warned his companion to keep away from him (during a partial regeneration which occurred during the Doctor's partial tenth regeneration, Jack did this as well). This would seem to imply that the energy released during the process posed some level of danger to Humans, and possibly that them being too close may pose a danger to the Time Lord. (DW: The Parting of the Ways, The Stolen Earth) However at least one regeneration occurred with other individuals seen in close proximity (although this was assisted by the transient Watcher, who may have helped to contain the regenerative energy). (DW: Logopolis)

Physical and mental change

During regeneration, the body of a Time Lord is reconfigured into a new form; the new form is generally, though not invariably, physically younger and healthier (in human terms) than the Time Lord's previous incarnation. The Time Lord might gain or lose height and body mass. After each regeneration there is often a marked change in personality. During the process of regeneration there are the genetic equivalent of 'bit errors' in the DNA of the regenerated cells. This is what causes the appearance of the Time Lord to change; because even the cells of the brain regenerate as well, their brain chemistry and organisation will change. Although the aspects of their personality caused by "nurture" will not change, the "nature" contribution to their personality will change. (BFA: The Sirens of Time) Time Lords of the Oldblood Houses, born with just one heart, grew a second heart upon regeneration. This included the Doctor, who in his first incarnation had only one heart. (MA: The Man in the Velvet Mask)

After-effects

During the first few hours of the regeneration, the Time Lord will often suffer from confusion, erratic behaviour and memory loss. The Doctor, in particular, though not so much other Time Lords, has exhibited mood swings and confusion. It took some time for the regeneration fifth incarnation to remember his own identity. (DW: Castrovalva) On one occasion, he attempted to strangle Peri to death before re-asserting control of himself (DW: The Twin Dilemma) and on another he almost crashed the TARDIS (DW: Children in Need Special) A Zero Room can help with this, as it removed all outside distractions. (DW: Castrovalva)

If they are knocked unconscious, the whole process might be started all over again. (DWN: The Power of the Daleks) After a while, the Time Lord's body will have settled down, though they can regrow limbs within the first 15 hours of the regeneration due to having enough residual energy. (DW: The Christmas Invasion) After his regeneration, the Doctor implied that his TARDIS helped the process along. (DW: The Power of the Daleks) Some Time Lords, however, may regenerate with little or no overt complications, for example, Romana. (DW: Destiny of the Daleks) Even after the physical transformation, changes might occur, as the Doctor believed could happen. (DW: Robot) The Doctor's hair, for instance, went from longer to shorter to longer in the space of a few days. (MA: Cold Fusion)

Limitations

Though Time Lords can regenerate after severe injuries- one Time Lord even starting to regenerate a complete body after being decapitated (EDA: The Shadows of Avalon), the process only being cut short when she is stabbed through both hearts before it can finish- regeneration does not seem to be guaranteed. The Doctor, for example, was at one point convinced that he was going to die at the hands of the Gelth (DW: The Unquiet Dead), although it is possible he meant the particular incarnation, and there have been numerous occasions in his lifetimes where survival -- including regeneration -- was not assured. Maxil implied that a fatal blast from a staser (an energy weapon used by the Chancellory Guard on Gallifrey) could prevent regeneration. (DW: Arc of Infinity) Stabbing or shooting a Time Lord through both hearts at the same time (EDA: The Shadows of Avalon, PDA: World Game), or drowning, if it happened quickly enough (DW: Turn Left) could also end a Time Lord's life regardless of how many regenerations they have left.

As well, the interference of some medications, such as anaesthesia, may disrupt or destroy the regenerative process. (DW: Doctor Who: The TV Movie)

The regenerative cycle

The Time Lords had a limited regenerative cycle of twelve incarnations, after which they had no more incarnations and would suffer permanent death. (DW: The Deadly Assassin, Doctor Who: The TV Movie) Time Lords can will themselves to die by regenerating when they have no more regenerations left to use, as Azmael chose to do. (DW: The Twin Dilemma) Other life forms (for example, the Minyans) could have hundreds. Rassilon apparently had physical reasons to impose this restriction. (BFA: Zagreus)

As with most such "rules" there were occasionally exceptions to the twelve regeneration limit. The High Council, offered the Master a new regenerative cycle if he complied with rescuing the various incarnation of the Doctor from the Death Zone. (DW: The Five Doctors)

The crew of the Minyans' ship the P7E, however, had had about a thousand regenerations, by which time, however, they wearied of life. (DW: Underworld) Mawdryn and his followers, who had stolen the Time Lords' regeneration technology, also had an apparently limitless number of incarnations, though they had no control over when it would happen and what form, often grotesque, they would have change into. Consequently, they also longed for death, making their mutations of a kind of de facto punishment by the Time Lords for stealing their technology. (DW: Mawdryn Undead)

Control over regeneration

Generally, regeneration is initiated when a Time Lord has been too badly injured to survive. However in some cases Time Lords have been known to exercise control over the process. Romana appeared to regenerate on a whim, (DW: Destiny of the Daleks) while Azmael initiated a thirteenth regeneration in order to end his life (DW: The Twin Dilemma). The process can also be stopped with some difficulty (DWN: The Power of the Daleks), as the Master did in order to spite the Doctor (DW: Last of the Time Lords). This is not always an option, however, as the Doctor notes fearfully that while his companion can die only once, he may have to repeatedly regenerate and live out all of his life times when the TARDIS stalls in the middle of space. (DW:Vengeance on Varos)

The degree of control that Time Lords have over their end appearance is unclear. The Master was able to make his next regeneration as young as the Doctor was at the time, though since most regenerations lead to younger bodies this may have been a coincidence. (DW: Utopia) Romana seemed adept enough at the process to custom design her new appearances, trying several bodies before finally deciding on a copy of Princess Astra. The Doctor criticised Romana for taking on the form of another person, suggesting such things were not unheard of. (DW: Destiny of the Daleks) In contrast to Romana, the Doctor did not appear to have much control over his post regeneration appearance; after his fourth regeneration he commented "that's the problem with regeneration, you never quite know what you're going to get" (DW: Castrovalva), and would restate this immediately prior to his ninth regeneration (DW: The Parting of the Ways) (Although the violent nature of his regenerations as opposed to Romana apparently triggering her regeneration on purpose might have something to do with this difference).

While skilled Time Lords can choose their new form with a voluntarily induced regeneration, the process has the potential to go horribly wrong and leave the Time Lord in a severely misshapen body. The problem is then often exacerbated by the Time Lord trying to solve the problem by immediately starting another regeneration instead of obtaining medical assistance, which only amplifies the defects in the regeneration. The end result of several too close regenerations, whether self-initiated or not, is inevitably a mutated monstrosity that can only be put out of its misery by complete disintegration. (DWN: The Twin Dilemma)

Some Time Lords were capable of momentarily regenerating, or partially regenerating. Though this could use up a lot of regenerative energy, it could give the Time Lord a new set of genes, allowing them to fool genetic sensors. The Master was able to do this, which he used in many of his schemes. The Doctor used this method to on the planet Purgatory in order to fool the genetic scanner used by the Landsknechte. (NA: Original Sin)

The Time Lords were apparently capable of controlling the regeneration of individual Time Lords, either forcing a regeneration, influencing the new appearance (DW: The War Games) or removing later regenerations (DW: The Ultimate Foe).

Unusual or failed regenerations

Failed regenerations

The Doctor feared, after his fourth regeneration that it had failed, at which time he asked for help in getting to the Zero Room of the TARDIS. (DW: Castrovalva) A metamorphic symbiosis regenerator can also provide help. (DW: Mawdryn Undead)

Meta-Crisis

The Doctor regenerating. (DW: The Stolen Earth)

A Time Lord can prevent death and regeneration by focusing the regenerative energies into a severed appendage, like the Doctor's hand. His hand siphoned off the excess energy that would have changed his appearance while the Doctor used just enough to heal himself from the injury sustained by the Dalek gun. This resulted in the appendage storing enough energy to actually grow a nearly identical Time Lord after it come in contact with Donna Noble. As a consequence, the Doctor appeared to regenerate and healed but did not change. (DW: Journey's End)

It is unknown if this used up one of the Doctor's regenerations.

Cross-species transformations

Though they did not undergo normal regenerations, as noted elsewhere, Mawdryn underwent many mutations of physical form. (DW: Mawdryn Undead) I.M. Foreman, a Gallifreyan (but not a Time Lord) absorbed the DNA around him and underwent indescribable changes as a result of mutations, transcending sex, species and even physical existence itself. (EDA: Interference - Book One, Interference - Book Two) Romana, prior to her regeneration in to her second incarnation, appeared to have taken on a Near-Human blue-skinned form. (DW: Destiny of the Daleks)

One account states that the TARDIS itself, rather than Romana, adopted this shape. (ST: The Lying Old Witch in the Wardrobe)

Aborted Regeneration

Occasionally, a regeneration will fail and the regeneration will abort. Though the Time Lord will have regenerated, they are severely deformed. Though Time Lord technology can treat this, in some occasions the damage will be too severe to fix.

After being shot by the War Lords, the War Chief was barely able to survive. While being taken back to the War Lords' planet, his body attempted to regenerate. Due to the massive injuries and the lack of medical care, this regeneration aborted, which meant he had two conjoined individual bodies, poorly fused together. (NA: Timewyrm: Exodus)

Scientific explanation

The exact mechanism that makes regeneration possible has not been stated. Varying explanations may or may not be compatible with each other.

• One explanation was that Cardinal Rassilon had been investigating a method of regenerating decaying and diseased tissue via a series of permanently carried self-replicating biogenic molecules. The cells of a Gallifreyan body could be repaired, restored and re-organised. This would result in a wholly new physical form. The brain cells would similarly be rearranged, though to a lesser degree, thus ensuring the new incarnation will replicate the memories and personality of the former incarnation. Rassilon intended for this mechanism only to be used upon the Gallifreyan elite. He also inputted a parameter of 12 regenerative cycles to avoid decaying biogenic molecules. (BFA: Zagreus)

• Another theory attributes regeneration to a "nanomolecular virus" that rebuilds the body much like the "self-replicating biogenic molecules". (EDA: The Gallifrey Chronicles)

• A third theory is that Time Lords have triple-helix DNA: the third strand was added by Rassilon to make regeneration possible. (MA: The Crystal Bucephalus)

• One partial explanation of the process links it to the release of massive amounts of a hormone known as lindos at moments of extreme trauma, with the hormone triggering the regeneration itself. Recently-regenerated Time Lords can be identified by the raised levels of lindos in their system. (DWN: The Twin Dilemma, BFA: Unregenerate!)

Specific regenerations

Time Lords

The Doctor

• Apparently succumbed to old age and/or fatigue (possibly accelerated by energy drain of Mondas). (DW: The Tenth Planet)
• A forced regeneration and exile to Earth by the Time Lords. (DW: The War Games)
• Radiation poisoning from the Great One's cave of crystals on Metebelis III. (DW: Planet of the Spiders)
• Fell from the Pharos Project radio telescope. (DW: Logopolis)
• Spectrox toxaemia exposure. (DW: The Caves of Androzani)
• Injured as the Rani attacked the Doctor's TARDIS. (DW: Time and the Rani)
• Died on the operating table while undergoing exploratory heart surgery by Dr. Grace Holloway. (DW: Doctor Who: The TV Movie)

In this instance, the Doctor physically died before he regenerated, at least in human terms.

• Unknown; presumably caused injuries from the Last Great Time War. (Prior to Rose)
• Cellular degeneration caused by absorbing the energies of the time vortex from Rose Tyler, which she in turn had absorbed from the heart of the TARDIS. (DW: The Parting of the Ways)
• Partial regeneration after being hit by Dalek fire, (DW: The Stolen Earth); aborted by redirecting the energy to his severed hand (DW: Journey's End)

The Master

• Used up most of his regenerations escaping from the Darkheart. (MA: The Dark Path)
• Used up his regenerations, up until his last, recovering from bomb blast set by Susan Foreman. (EDA: Legacy of the Daleks)

These accounts contradict each other somewhat. Possibly, not all were used up in the two instances.

• Utilized the power of the Source to steal the body of Tremas. (DW: The Keeper of Traken)
• Stole the body of the Human Bruce. (DW: Doctor Who: The TV Movie)

Neither of these new bodies were, strictly speaking, regenerations.

• Regenerated to survive wound from gun fired by Chantho. (DW: Utopia)

The Master had been resurrected to fight the Last Great Time War at this point, and probably had a new regenerative cycle.

Romana

• Regenerated into duplicate body to Princess Astra. (DW: Destiny of the Daleks)

One account says that she did so to prevent her possession by the evil entity Pandora (BFG: Lies), another that the Key to Time had secretly harmed her (ST: The Lying Old Witch in the Wardrobe).

• Regenerated into an incarnation more suited to fighting the War with the Enemy. (EDA: The Shadows of Avalon)
• Romana may also have regenerated a third time as a result of the War. (PDA: Tomb of Valdemar)

Rassilon

Rassilon was said to have achieved a cycle of perpetual regeneration, becoming immortal. It was for this secret that Lord President Borusa sent four of the Doctor's incarnations and their companions into the Death Zone, where Rassilon lay in eternal sleep in the Dark Tower. (DW: The Five Doctors)

Humans

The Brigadier

Regenerated in 2012, which renewed his youth. (NA: Happy Endings)

Chris Cwej

• Regenerated by force to survive radiation poisoning (BNA: Tears of the Oracle)

Behind the Scenes

• Regeneration was first introduced when the First Doctor (William Hartnell) changed into the Second Doctor (Patrick Troughton) in the closing moments of The Tenth Planet. Tradition has it that Hartnell himself thought up the idea of the Doctor being able to change into a new body as a means of keeping the series going after his departure.

In The Power of the Daleks, the next story, the Doctor said that he had been "renewed", and also said that the change was partly due to the TARDIS, partly to himself, without elaborating. Originally, the Production team meant for the Doctor to have used the TARDIS to reverse time and "rejuvenate" himself, though they may have abandoned this explanation by the time Patrick Troughton took over the role.

The change in the Doctor's appearance was meant to occur several stories earlier, during The Celestial Toymaker, with the Toymaker capriciously having changed the Doctor's appearance out of spite. (The Doctor is invisible and unable to speak for most of the story anyway.) The reason for the change of plan is unknown. Either it was decided to retain Hartnell in the role for a few more stories, or the actor was accidentally issued with a new contract by mistake, making it impossible to recast the Doctor at that moment in time. (A plot device similar to this would occur in The Mind Robber to cover Frazer Hines' temporary replacement by his cousin, Hamish Wilson, after Hines contracted an illness.)

• The changeover was not actually referred to as "regeneration" until the end of Planet of the Spiders, when the Third Doctor (Jon Pertwee) changed into the Fourth (Tom Baker). Prior to this, the Doctor was simply described as having "changed his appearance."

• Fans and the general public have long speculated as to whether the Doctor could change sex as a result of a regeneration. The Time Lord I.M. Foreman having changed sex as a result of regeneration implies that this can happen. The Rani has been referred to as a "Time Lady" as opposed to a "Time Lord", suggesting that Gallifreyans have both male and female species and can only regenerate into bodies of that assigned gender. Female versions of the Doctor appeared in the non-canonical The Curse of Fatal Death and in the Doctor Who Unbound story Exile.