The Someone Like You singer, who split from husband Simon Konecki last year, shared a pic revealing her slimmer frame.
Adele smiled for the camera while standing outside her LA home alongside a giant floral wreath, wearing a black dress.
“Thank you for the birthday love,” she captioned the photo. “I hope you’re all staying safe and sane during this crazy time.
“I’d like to thank all of our first responders and essential workers who are keeping us safe while risking their lives! You are truly our angels.”
She added: “2020 okay bye thanks x.”
The multi Grammy and Brit award-winning superstar has been following a new fitness and healthy eating plan following her divorce from husband Simon Konecki, which was finalised last September, citing “irreconcilable differences”.
The couple share a son, seven-year-old Angelo.
In February, Adele appeared to confirm she had a new album on the way later this year.
She performed at the wedding party of her friend, author Laura Dockrill and Maccabees guitarist Hugo White, and in videos uploaded by guests she said: “Expect my album in September.”
Her most recent album was the chart-topping 25 in 2015.