Hearing Loss in One Ear: Causes, Tests and Next Steps

01Unilateral hearing loss

Unilateral hearing loss and severity

Unilateral hearing loss means that one ear hears less well than the other. It does not always mean deafness: it can be a mild or partial loss, a hearing loss that is worse on one side than the other (asymmetrical hearing loss), or, at the far end, single-sided deafness, where one ear has little or no useful hearing.

NHS Greater Glasgow and Clyde ENT guidance explains that hearing may be asymmetrical for many reasons, including childhood infection, previous surgery and causes that are never found, and that it may be longstanding. Others notice it suddenly, sometimes on waking. Because the cause and urgency differ so much, the first questions are always when it started and how quickly.

02Sudden loss

Sudden change needs immediate assessment

The NIDCD describes sudden sensorineural hearing loss, often called sudden deafness, as an unexplained, rapid loss of hearing, either all at once or over a few days, caused by a problem in the inner ear. It frequently affects only one ear. The Glasgow guidance defines it as loss of hearing in one ear that occurs over less than 72 hours.

People often notice it on waking, when using the phone with that ear, or after a loud “pop”. It may come with ear fullness, dizziness or ringing (tinnitus). The NIDCD warns that people sometimes delay seeing a doctor because they assume it is allergies, a sinus infection or earwax, and stresses that it should be treated as a medical emergency: delay can make treatment less effective, and timely treatment increases the chance of recovering at least some hearing.

Do not wait for an online hearing test, decongestants or home remedies to work. Our guide on sudden hearing loss explains this situation in more detail.

03Gradual loss

Gradual or longstanding hearing changes

When hearing in one ear has changed slowly, or has been reduced for a long time, the cause is often in the outer or middle ear. The Glasgow guidance describes several conditions that cause one-sided hearing loss without pain:

• fluid behind the eardrum (otitis media with effusion), much more common in children but possible in adults, sometimes after a cold; if it lasts more than three weeks, routine ENT referral is advised
• a hole in the eardrum (chronic otitis media with perforation), which may cause intermittent discharge, especially after water gets in, and some hearing loss
• cholesteatoma, a growth of skin cells behind the eardrum that may cause foul-smelling discharge and hearing loss and, if active disease is untreated, serious complications
• earwax build-up, which is usually managed in primary care

The guidance also notes that, rarely, fluid in one ear only can be caused by a problem blocking the tube that connects the ear to the back of the nose, which is one reason persistent one-sided symptoms in an adult should be examined. If your main symptom is a muffled ear, our guide on muffled hearing may also help.

04Types

Conductive and sensorineural causes

Clinicians separate hearing loss into two broad types. Conductive hearing loss happens when sound cannot pass properly through the outer or middle ear, for example because of wax, fluid, a perforation or cholesteatoma. Sensorineural hearing loss comes from the inner ear or the hearing nerve.

For sudden sensorineural loss, the NIDCD says only about 10 percent of people have an identifiable cause. Possible causes it lists include:

• infections and head injury
• autoimmune diseases
• some medicines used for cancer or severe infections
• blood circulation problems
• neurological conditions such as multiple sclerosis
• inner ear disorders such as Ménière’s disease

The NIDCD adds that when sudden hearing loss affects only one ear, a tumor on the hearing nerve should be ruled out. The Glasgow guidance notes that sudden loss with sudden spinning dizziness may be inner ear inflammation, but that a stroke should be considered. Do not stop a prescribed medicine on your own because you suspect it; discuss it with the prescriber.

05Associated symptoms

Tinnitus, fullness and associated symptoms

Symptoms that come with the hearing loss help clinicians narrow down the cause. According to both sources, these may include:

• ringing or other noise in the affected ear (tinnitus)
• a feeling of fullness or pressure in the ear
• dizziness or a spinning sensation
• discharge from the ear, sometimes foul-smelling
• a pop at the moment hearing changed

Some combinations need emergency care: the Glasgow guidance asks for emergency ENT referral when a person with cholesteatoma develops weakness of the face on the same side or signs of balance organ failure. For ringing that persists after the cause has been assessed, see our guide on tinnitus treatment.

06Assessment

Ear examination, hearing tests and further evaluation

The first step is to look into the ear to rule out wax, fluid, a perforation or other causes in the outer and middle ear. The Glasgow guidance describes an ear examination, a simple spoken-voice hearing test and tuning fork tests, and a check of the cranial nerves when sudden loss is suspected, because abnormal findings may point to pressure on the hearing nerve.

The NIDCD explains that if no obvious cause is found, the doctor should arrange pure tone audiometry within a few days. This test measures how loud sounds of different pitches need to be before you hear them in each ear, and it confirms whether the loss is sensorineural.

If sudden sensorineural loss is diagnosed, further tests may look for an underlying cause. The NIDCD lists blood tests, imaging, usually magnetic resonance imaging (MRI), and balance tests. Which tests are needed depends on the findings, so not everyone with one-sided hearing loss needs a scan.

07Treatment

Treating the cause and rehabilitation choices

Treatment depends on the cause. In the Glasgow guidance, persistent fluid, a discharging perforation or cholesteatoma are managed by keeping the ear dry, prescribed ear drops when there is inflammation or discharge, and ENT referral when there is no improvement or when surgery or a hearing aid would be considered. It notes that surgery to close a perforation does not usually improve hearing, but can reduce discharge and help some people wear a hearing aid.

For sudden sensorineural loss, the NIDCD says the most common treatment is corticosteroids, taken by mouth or injected through the eardrum, ideally as soon as possible; treatment delayed for more than two to four weeks is less likely to help. This is a medical decision, not one to make with leftover tablets. About half of people recover some or all of their hearing on their own, usually within one to two weeks.

When hearing in one ear does not return, the Glasgow guidance lists rehabilitation options:

• a hearing aid in the poorer ear, or in the better ear if that ear also has some loss
• CROS or BiCROS devices, worn on both ears, which pick up sound on the side with poor hearing and send it to the better ear
• a bone conduction device, surgically placed on the side with poor hearing, which sends sound to the other ear

For severe loss, the NIDCD mentions cochlear implants as another option for some people. Each option has its own suitability criteria, and none restores normal hearing in every case.

08Daily life and follow-up

Communication, follow-up and an onset record

With one ear hearing less, it can be harder to tell where sounds come from and to follow speech in noise or when the speaker is on your poorer side. Sitting with your better ear toward the conversation and reducing background noise can help while you wait for assessment.

Before the appointment, write down a short record. It does not replace urgent care, but it helps the professional:

• the date and time you first noticed the change, and whether it was sudden or gradual
• which ear, and whether it is getting better, worse or staying the same
• tinnitus, fullness, dizziness, discharge, pain or any facial weakness
• recent colds, ear infections, injuries, loud noise exposure, flights or diving
• medicines you take, previous ear surgery and earlier hearing tests
• situations where you struggle most: phone calls, groups, noisy places

For adults with gradual or longstanding hearing changes and no warning signs, our ENT practice in Bilbao offers scheduled assessment with examination and hearing tests (consultations are in Spanish). Sudden hearing loss needs same-day medical care, not an online form.

09Sources

Where the sources differ

The NIDCD page on sudden deafness was last updated in September 2018, so some details may not reflect the latest guidance; the Glasgow ENT guidance was reviewed in May 2025 and is written for primary care professionals rather than patients.

The sources describe the timing of sudden loss slightly differently: the NIDCD says “all at once or over a few days”, while the Glasgow guidance sets a limit of less than 72 hours. The NIDCD also gives a hearing test threshold used by clinicians to diagnose sudden loss, but notes that more subtle sudden changes can also be diagnosed. Neither is a rule for deciding whether to seek help: any sudden change should be checked the same day.

Finally, the Glasgow guidance acknowledges that national advice recommends same-day ENT referral for sudden loss, but that local audiology capacity means patients there are referred urgently instead. That reflects a local service limitation, not a reason to wait wherever you are.

10Summary

In summary

Hearing loss in one ear can be mild or complete and can come from the outer and middle ear, such as fluid, a perforated eardrum, cholesteatoma or wax, or from the inner ear and hearing nerve. Sudden loss over hours or a few days is an emergency, even without pain, because early treatment improves the chances of recovery; neurological symptoms need emergency care.

Gradual or longstanding loss needs an ear examination and hearing tests, sometimes with further tests. Treatment targets the cause, and if hearing does not return, hearing aids, CROS devices or bone conduction devices can help, although they do not restore normal hearing in the affected ear. A clear record of onset, symptoms and difficult listening situations makes the assessment more useful.