Blood type

A blood type, also known as blood group, was a classification of blood.

Nature
Some vampires favoured specific blood types, sometimes because they were old and sickly and could metabolise some types more easily than others. However, most were indifferent to it.

The Corsair knew a way to tell an individual's blood type by measuring "the body's Qi² levels during an ecstatic state". (PROSE: The Bloodletters)

Known types
On Earth, A-positive was a common type, with one third of humanity in 2006 being A-positive. This was exploited by the Sycorax, who used a sample of A-positive blood in Guinevere One to hypnotise all A-positives via blood control. (TV: The Christmas Invasion) When project head Daniel Llewellyn apologized to Prime Minister Harriet Jones about the blood sample, she responded that it was not as bad as it could have been as if he had used O group blood, which would have left half of the Earth's population affected. (PROSE: The Christmas Invasion)

Charley Pollard's blood type was AB-negative. (AUDIO: Absolution)

The First Doctor had TL-positive blood. (PROSE: A Big Hand for the Doctor) According to Dr Lomax, the Third Doctor's blood had a blood type unidentifiable as human blood, as shown by its platelet stickiness. (TV: Spearhead from Space) Steven Taylor thought the First Doctor's unidentified blood type barely even resembled blood as seen in humans. (AUDIO: An Ideal World)

Other blood types existed among other humanoid species. Q-Negative was a "relatively rare" universal-donor type, found, among others, in the native species of Hoppiq Minor. (PROSE: The Bloodletters)