Dr David McCarthy, a consultant anaesthetist, was on call at Manchester Royal Infirmary when the bombing occurred.
He wrote on Facebook: “An atrocity was carried out which has had an unmeasurable impact on countless lives.
“Many casualties were bought to our department.
“Once an incident had been declared, dozens upon dozens attended to help.
“The response from my colleagues represented everything great about this country. Compassion. Empathy. Tireless self sacrifice and above all else profound unity.
“Staff from almost every imaginable background, race and religion came together and put their all into caring for those wounded.
“I was proud to be a small part of such a dedicated team, every bit as diverse as our community.”
Dr McCarthy said he knew people in the UK would “not allow the actions of individuals to divide our society” and said “together we are stronger”.
He added: “My profound thanks to those who helped throughout the night and to those who attended in large numbers to continue our efforts into what will be a difficult day.
“My deepest sympathies to those who have lost loved ones. I sincerely hope you have the support of those around you.
“Thank you to those that have supported me xx”