Is it permissible to agree with a human doctor to refer patients to a private diagnostic laboratory in exchange for a percentage of the profits?

If your laboratory meets the patient's need for laboratory analyses, then there is no harm for the doctor to direct the patient to you and take a commission for it. However, if the laboratory does not meet the patient's need, or if the patient does not need analyses, then it is not permissible for the doctor to refer them, and any money taken in this case is considered bribery and consuming people's wealth unlawfully, which is forbidden; due to the saying of the Prophet, peace and blessings be upon him: "The Messenger of Allah, peace and blessings be upon him, cursed the briber and the bribed," and "He who deceives us is not of us."