A doctor who had previously been struck off the medical register but prescribed slimming pills at clinics across England has been jailed for 18 months.
Sudesh Madan, 57, of Homeway, Romford, Essex, had previously admitted four counts of possession with intent to supply a controlled drug.
She sold phentermine and diethylpropion slimming pills at five Easy Slim clinics, St Albans Crown Court heard.
Police said Madan led her patients to believe she was a doctor.
Hertfordshire Police executed warrants at the clinics in Welwyn Garden City, Harlow in Essex, Wakefield and Huddersfield in West Yorkshire and Barnsley in South Yorkshire in December.
They were alerted when their colleagues in Essex interviewed a woman about an unrelated offence and discovered she had been taking slimming pills prescribed by Madan, who was struck off the medical register by the General Medical Council (GMC) in 2001.
A week's worth of pills, which could help suppress appetite, would typically cost £20, police added.
The police searches uncovered 24,599 phentermine and 13,269 diethylpropion tablets and capsules.
Det Insp Ian Butler, said: "Sudesh Madan ran a large-scale operation across the country, callously posed as a doctor and, without any care for her patients, prescribed these slimming pills, which could have put them at risk.
"We believe her motivation was greed and we are determined to use our powers to remove any profits she made from her actions."
Police said anyone who may have been prescribed the tablets at an Easy Slim clinic should contact their GP or a pharmacist for advice.
Madan had been struck off by the GMC after being found guilty of serious professional misconduct relating to the prescription of unlicensed slimming drugs.