He was born in 1617 at Tring, Hertfordshire, and educated at Eton, whence he was elected to a scholarship at King's College, Cambridge, in 1634.
On 27 July 1649 he was admitted a candidate of the College of Physicians of London, and a fellow on 25 June 1651.
Collins was incorporated at Oxford in his doctor's degree in May 1650, and about that time was, by an ordinance of parliament, elected a fellow of New College in that university.
He settled in London; was appointed censor of the College of Physicians in 1659, 1669, and 1679; was Harveian orator in 1665, and again in 1682; Gulstonian lecturer in 1675; and registrar from 1682 to his death.
To him Wood erroneously ascribes the authorship of 'The History of the present State of Russia,' printed at London 1671.