Dr Alex George has said the past year has been the hardest of his life while marking the anniversary of the first national lockdown on 23 March.
The former Love Island contestant has been working in A&E at University Hospital Lewisham during the pandemic.
It has also been a challenging year for the medic after his brother Llyr took his own life aged 19 in 2020.
The former Love Island contestant, who works in A&E at University Hospital Lewisham, also praised the "incredible" NHS in his Instagram post.
Reflecting on the beginning of pandemic, he said: "A year ago today we went into the first lockdown. I could never have imagined the year that followed. The speed we went from a few isolated cases, to entire departments of covid patients, was terrifying.
"As we approach 130,000 deaths in the UK, I would like to take a moment to honour those who lost their lives. I know that I will never forget the people that I cared for, it will stay with me my entire life. I send my love to all those who have lost loves [sic] ones during the last year."
George posted his message alongside a throwback picture of himself and other NHS staff posing in personal protective equipment.
He went on: "I would also like to take a moment to reflect on how incredible the NHS has been throughout, we pulled together and looked after each other as well as giving 150% for our patients.
"We had to adapt and learn quickly, this photo was taken when we still knew virtually nothing about Covid. It has been a privilege and an honour to work alongside you all.
"As we look forward, to the future, I hope and believe that there are better days ahead. Personally, it has been the hardest year of my life, thank you to each and everyone of you that got me through. There is always hope of a better day."
After his brother's death, George campaigned for better mental health support in the UK which led to a meeting with Boris Johnson.
The prime minister appointed him as youth mental health ambassador and he will act as an advisor to the government on the issue.
Watch: Dr Alex George says mental health leads are needed in every school