Taken from the websites
Birmingham: Applicants must have Chemistry and Biology A level, both at grade A (the third A level must also be at grade A) and an AS level at grade B/A – these must be obtained at one sitting; Human Biology may be offered, but not in addition to Biology.
Sheffield: At Sheffield we do not give preference to any particular subject for this third A-level choice. Similarly preference is not given to applicants who are taking 4 A-levels or additional AS levels.
Leeds: The third A-level may be any subject excluding General Studies or Critical Thinking. Those taking a fourth A2 subject will not have an advantage over those taking three.
Manchester: Grades AAA. This must include Chemistry, Biology and a third A level at grade A plus one further AS level at grade B or above.
King's: Chemistry and Biology, at least one at A-level, the other must be at AS level. If A-level Maths is offered, Further Maths is acceptable at AS-level only. GCSE requirement: at least grade B at English Language and Maths, if not offered at A/AS-level.
Bristol: to include A grades in both Chemistry and one other lab-based science. Grade A Biology at AS if not taken to A-level (Biology is the preferred second subject at A-level).
Liverpool: A level Chemistry and Biology. The third subject may be anything other than General Studies or Critical Thinking.
Newcastle: AAA including Chemistry and Biology. General Studies, Critical Thinking and a foreign language which is the applicant's first language are not accepted.
Dundee: Biology and a science (Chemistry, Maths or Physics) at A-level.
Glasgow: Must have A-level Biology and Chemistry (both at Grade A).General Studies is not acceptable as a third subject at A-level.
Barts: Chemistry and Biology at AS level, at least one at A-level. If both subjects not taken to A-level, a second science A-level is required. If you are planning to drop either Chemistry or Biology before A2, you must attain a B grade in that subject at AS level. If A-level Maths is offered, Further Maths is acceptable at AS-level only. General Studies and Critical Thinking are not accepted subjects at AS and A-level.
Cardiff: Our current entry requirements are AAA grades to be achieved from three A-Levels with A grades in Chemistry and Biology.
We do not give preference to an applicant whose third A-Level is in a Science subject.
Queen's Belfast: Three A-levels are required to include GCE Chemistry + at least one from Biology, Physics and Maths. A maximum of one VCE/Applied subject at either A-level or AS-level (not both) will be counted. If Biology is not offered at GCE A-level, it is required at GCE AS grade B or better. Mathematics and Further Mathematics cannot be counted together at A-level but one may be counted at A-level and the other at AS-level.
Pretty much all the dental schools do not give preference to a 3rd science subject at Alevel.