He was born in Great Waldingfield, Suffolk, the third son of Thomas Crooke, rector of the parish and later reader at Gray's Inn; his mother's family surname was Samuel.
His eldest brother Sir Thomas Crooke achieved distinction as the founder of Baltimore, County Cork.
[2] Thomas and another brother Samuel Crooke (who was also a clergyman) were, like their father, inclined to Calvinism; Helkiah, on the other hand, is said to have leaned towards Roman Catholicism.
[5] For some time he practised privately in Suffolk; his first application to join the Royal College of Physicians was unsuccessful, but he was admitted in 1613.
Possibly through the influence of his brother Thomas, who had some acquaintance with King James I, he was appointed physician to the Royal Household.
In addition, it contained frank illustrations of the human sexual organs, leading the Church authorities to denounce it as "indecent".
His admirers called him a reformer who pioneered the humane treatment of the mentally ill:[8] his critics claimed that he embezzled funds and was usually absent from the hospital, deputising his duties to his son-in-law, Thomas Bedford.