She initially shared her symptoms on Sunday morning, writing: "Day Nurse is a wonderful medicine isn't it? Feeling pretty grim (not Covid) with blocked ears, sore throat and achy muscles. 2 tablets have got me up enough to make a cuppa… exhausted now so back to bed. Both cats nursing me."
WATCH: Fern Britton makes rare comment about her daughters
Fern's followers were quick to send their support, writing: "Sending all the love Fern. Nowhere quite like bed when you're poorly," while another said: "I hope you recover very soon (definitely animals make the best companions when you feel poorly."
Just two hours after her first post, Fern took a turn for the worse, sharing a photo of a positive Covid test, writing: "So last night's test was negative, but now…"
Fern's fans flooded her with sympathy and well-wishes, to which she replied: "You are all so lovely! Lapping up the sympathy and sending love to everyone who is suffering. Back to bed."
Fern Britton shared the Covid symptoms she's experiencing
The author, whose latest book The Good Servant launched earlier in June, worried fans in March when she shared she was feeling under the weather.
At the time she said: "I'm so achy today. No Covid but whole bod in need of a recharge," and fans were quick to check she was sure she didn't have Covid.
One wrote: "Hope you are better soon. If you have done a covid test, remember it is better to do it in the throat and not nose," while another advised: "I tested negative even though I had sore throat and achey. Did another test later in the day and was positive."
If you're feeling under the weather, stock up on Fern's favourite Day Nurse
Day Nurse Cold and Flu Capsules, £7.50, Boots
Fingers crossed Fern is back on top form soon.
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