The sudden loss of hearing is not something you can ignore. Even a dip in your hearing level, where you can still hear but noticeably not as well as before, is something you need to have investigated quickly. It is possible for the condition to have a simple cause, but in many cases the causes are ones that need immediate medical intervention. A sudden hearing loss is an emergency.
Sudden hearing loss can happen in one ear (unilateral) or very rarely both ears (bilateral). The loss isn't called sudden for nothing; it comes on very quickly, and depending on the cause, can happen instantaneously. You're hearing fine one second and noticing a loss the next. A common complaint from patients is that they had normal hearing one night, went to sleep, and woke up with hearing loss. A plugged feeling sometimes occurs with the loss, leading many to think they just have a temporary allergy or virus. However, the cause could be much more serious, such as a virus that targets and harms the ear, a stroke in the inner ear, or a tumor.
One self-test you can do is to try to hum. If you can't hear yourself humming in the ear that feels plugged up, you need to visit an ear nose and throat doctor immediately. If you do hear the humming in the ear in which you're having trouble, then you may be dealing with an allergy -- or you could have fluid or a plug of wax. Both of those need to be checked out, if for no other reason than to take care of the condition and get your hearing back as quickly as possible.
A complete hearing evaluation is necessary to get a full picture of what's happening inside your ears. The evaluation consists of a series of tests designed to look at each portion of your ear, from the outer canal to your inner ear and beyond. You may have to get an MRI to rule out the possibility of an acoustic neuroma, which is a tumor on your auditory nerve; these tumors can occur in up to 3% of sudden hearing loss cases. They don't spread, but they can grow and have progressively worse effects on your hearing.
Additional tests, such as blood tests are rarely needed to check for diseases that can affect your hearing, such as infections, autoimmune disorders, Lyme disease, and other conditions.
A sudden loss of hearing is treated best with oral steroid pills (prednisone) and injection of steroids into the ear (intratympanic injection). If the hearing loss is caused by ear wax or fluid, other treatment is performed.