The phrase "admitted at once" is correct and usable in written English.
It can be used to indicate that someone acknowledged or confessed something immediately or without hesitation.
Example: "He admitted at once that he had made a mistake in his calculations."
Alternatives: "confessed immediately" or "acknowledged right away".
Four breeds will make their debut at Westminster this year, the most to be admitted at once since 1991.
She was admitted at once, earning a bachelor's degree in education there in 1933 and a master's in psychology two years later.
According to his colourful but unreliable memoirs, Massenet auditioned in October 1851, when he was nine, before a judging panel comprising Daniel Auber, Fromental Halévy, Ambroise Thomas and Michele Carafa, and was admitted at once.
Let's admit at once that the Leoben facility isn't the Jesus Prison: It's not going to single-handedly heal us and carry us up to Paradise.
Quentin Bell wrote in The Times Literary Supplement: "[The book] begins bravely and fairly by presenting the greater part of the author's case and admitting at once that 'it all sounds terribly unlikely'.
Of the 917 YAS, 321 (35.0%) were admitted to a hospital at least once during their follow-up period; whereas among the 4585 controls, 889 (19.4%) were admitted at least once.
Over the 3 years, 49% of people with type 1 diabetes were admitted at least once accounting for 33,516 hospital admissions (2.8 hospital admissions per person on average if admitted at least once).
Two hundred and ninety-nine patients were admitted at least once.
Patients and methods This was a retrospective single-center study of patients with HM admitted at least once to a university medical ICU, from 2003 to 2013.
Only 51 children (13.7%) were admitted at least once in the course of this surveillance (six children were admitted twice, six admitted three times, two admitted four times and one admitted five times).
Between January 1st, 2003 and June 30th , 2009 682 patients were admitted at least once to the cardiology department or to the cardiothoracic surgery unit of Brest University Hospital with non-rheumatic or rheumatic mitral (valve) insufficiency.
