The former world number five and 2012 French Open runner-up tested positive for banned drug letrozole.
The Court of Arbitration for Sport accepted medication taken by her mother found its way into a family meal.
But it said Errani, 31, was guilty of a “light degree of fault” which justified a 10-month ban.
She reacted by saying: “I am really disgusted by this matter. I don’t think anything similar has ever happened or been managed – in my humble opinion – in such a shameful manner.”
The decision followed appeals by the Italian anti-doping agency, which asked for a longer ban, and Errani, who wanted her voided results to be reinstated.
Errani, who reached the final four of last week’s Croatia Bol Open but withdrew before her semi-final match, must now serve another eight months of suspension.
The winner of five Grand Slam doubles titles was initially banned for two months by the International Tennis Federation (ITF) in August 2017. Her results from 16 February to 7 June that year were declared void.
Errani said her mother had been using the drug as part of her breast cancer treatment and had dropped some pills on a kitchen worktop where tortellini and broth were later prepared.
Letrozole increases lean body mass and was banned by the World Anti-Doping Agency (Wada) over concerns it was being abused by bodybuilders.
An independent tribunal, appointed by the ITF, said there was no evidence it would enhance the performance of an elite tennis player.
‘A very unfair treatment’
Errani’s mother and father told a tribunal hearing in July 2017 that after the positive finding, they carried out an experiment which found the drug dissolved in a broth, plus a meat mixture for tortellini, without being detectable.
“I never took any performance-enhancing substance in all my life, I love tennis too much to do something like that,” said Errani.
“I find this a very unfair treatment and I want to shout it, holding my head up high, because I am sure I have nothing to reproach myself about.”
In 2012 Errani stopped working with Luis Garcia del Moral, one of the doctors at the centre of cyclist Lance Armstrong’s doping scandal.
“I’m not interested in keeping working with a person that is involved in these things,” she said at the time.