The 29-year-old - a former Arsenal forward - arrived at the club in the summer of last year after spells in the USA and Spain, including a stint at Real Madrid.
Ubogagu grew up in the States and featured at youth level for the US Women's national team before returning to play for the Houston Dash in 2016, and she moved to the Orlando Pride one year later.
During her time in the USA, Ubogagu was given two forms of medication by a doctor to treat acne, and she continued to use the medication following her arrival at Tottenham last year.
However, Tottenham have claimed that the forward was unaware of the medication - spironolactone - being on the banned substances list, which led to an FA and UK Anti-Doping (UKAD) investigation.
Ubogagu has not featured for Tottenham since January following a provisional suspension, and the club have now confirmed that the England international has been charged with the violation and banned for nine months.
"We can confirm that Spurs Women forward Chioma Ubogagu has been charged with an anti-doping violation and has accepted a nine-month suspension. The FA and an independent tribunal reached the decision on Friday 22 April," a statement read.
"In November 2021, Chioma requested a repeat prescription from the Club doctor who alerted the relevant bodies; the FA and UK Anti-Doping (UKAD) about the use of a banned substance. The FA accepts that Chioma did not take the medication, spironolactone, with a view to intentionally securing an illegal advantage.
"Both the Club and Chioma fully cooperated with the FA and UKAD during the disciplinary process and Chioma has been unavailable for selection since the provisional suspension was imposed in January.
"Chioma takes full responsibility for the charge and deeply regrets her actions admitting a lack of knowledge and awareness on her part."
Ubogagu is hopeful that her "mistake" can help others avoid a similar fate, with the forward saying: "I am so sorry to my teammates and staff that I can't be out on the pitch.
"The Club has been fully supportive throughout this entire process, and I am so appreciative of all their help. My faith, family, and close friends have helped me immensely in this difficult time. I am eager to be back soon now that this has been resolved.
"I want to make clear that the medication had no performance-enhancing effects for me, but I still made the mistake of not being as diligent as possible, and as a result I am unable to play the game I love until I serve my suspension. While my dermatologist is aware of my profession, it is also my responsibility to know more about the medications I am prescribed.
"I plan to share my story and educate others on the severity of what can happen, and I hope I can help other athletes avoid situations like mine in the future."
Ubogagu made 10 appearances for Tottenham in the 2021-22 WSL season - starting four of them and claiming one assist in a 2-1 win against Manchester City back in September.
The ex-Gunner has already served four months of her initial suspension and will be eligible to return to action in October.