Doctors certificate - up to what date?

[UserThenLotsOfNumbers]

I've had the misfortune of being off work with gastroenteritis since last Wednesday.
Tomorrow is day 8 and I'll need a doctors note to cover my absence. I understand the doctor will sign me off work from the start of my absence until tomorrow (when I'll be seeing them) but can I ask to be signed off for the rest of the week as still feeling unwell/exhausted? Or will they say no? I've never been in this position before so not sure how it works. It is getting better but I still feel awful. Thanks.

You'll need to self certify for the first seven days, then your doctor will decide whether to give you a fit note from day eight onwards. You can ask to be signed off for longer, it will be up to your doctor as to whether they feel you are fit for work or not.

Thanks NoBaggyPants, that's useful to know. I'm worried they'll say I'm ok when I'm really not. Hopefully they'll take pity on me!