I can't see how they could be reliable, as it would depend on how loud your speakers were, where you were sitting, whether a 747 was landing in your back yard etc. These things need to be done under controlled conditions, surely?
We've both recently had a free hearing test done at our local independent optician. Whilst my hearing is not perfect, my other half was advised to see our gp and now has a hearing test booked at the surgery.
Worth having it done, for free, by a person who can advise you.
An online hearing test should be used just as a check of your hearing to assess whether you have a potential loss.
If necessary this can be then followed up with a check with a professional whether this is through the NHS or by going privately. If going via the NHS, your GP will refer you to your local audiology department. High Street stores such as Boots and Specsavers will do free tests and some independent private companies will do this as well (others might charge).