Unilateral Hearing Loss: What It Is, Causes, and When to Get Checked
Unilateral hearing loss means one ear hears less while the other hears normally. It can be mild or severe. If it came on suddenly, it is a medical emergency. Here is what unilateral hearing loss is, how it differs from single-sided deafness, common causes, how it is evaluated, and when to seek care urgently.
Key takeaways
- Unilateral hearing loss means one ear hears less. It can be mild or severe, with normal hearing in the other ear.
- It is not the same as single-sided deafness (SSD). SSD is the severe-to-profound, clinically unaidable subset of unilateral loss.
- If it happened suddenly, it is an emergency. NIDCD and NIA say to treat sudden hearing loss as a medical emergency and see a doctor immediately. Delaying treatment can make treatment less effective.
- Causes include infections, trauma, sudden loss, Meniere's, and tumors. ASHA lists hearing loss that runs in the family, problems with the outer, middle or inner ear, some syndromes, illnesses or infections, loud noise exposure, and traumatic brain injury. Also, a benign tumor on the hearing nerve.
- Evaluation starts with a hearing assessment. For sudden sensorineural hearing loss, AAO-HNSF recommends MRI or ABR to evaluate for retrocochlear pathology.
Unilateral hearing loss means one ear hears less while the other hears normally. It can be mild or severe. If it came on suddenly, treat it as an emergency (see box below).
Sudden sensorineural hearing loss often affects only one ear and can happen all at once or over a few days. NIDCD and NIA say to treat sudden hearing loss as a medical emergency and see a doctor immediately. Delaying diagnosis and treatment can make treatment less effective. Read our sudden hearing loss emergency guide for what to do next.
What unilateral hearing loss is
Unilateral hearing loss is hearing loss in only one ear, with normal hearing in the other ear. According to the American Speech-Language-Hearing Association (ASHA, last reviewed May 1, 2026), the hearing loss can range from mild to severe.
ASHA notes that someone with unilateral hearing loss (UHL) can have problems determining where a sound is coming from (localization). A peer-reviewed review published in The Journal of Clinical Medicine (Snapp & Ausili, published April 3, 2020) describes how profound unilateral hearing loss significantly impairs spatial hearing abilities, which leads to a reduced ability to understand speech in competing noise and to localize sounds.
For children, ASHA says children with UHL are at higher risk for academic, speech, and social difficulties than their normal-hearing peers. This may be because UHL in children often goes unidentified, and they do not receive the treatment or support that could help them.
On an audiogram, unilateral hearing loss shows as one ear's symbols sitting much lower than the other's. See our guide to reading an audiogram for how to interpret that pattern.
Unilateral hearing loss vs single-sided deafness
Unilateral hearing loss and single-sided deafness are not synonyms. Unilateral hearing loss covers any degree of hearing loss in one ear, from mild to profound.
Single-sided deafness (SSD), by contrast, is the severe-to-profound subset. The Journal of Clinical Medicine review defines SSD as profound unilateral sensorineural hearing loss, often termed single-sided deafness, referring to clinically unaidable hearing, as defined by severe-to-profound hearing thresholds with a poor word recognition ability.
The distinction matters because whether the poorer ear can still use amplification shapes which options a clinician discusses.
Common causes of hearing loss in one ear
ASHA lists the following causes of unilateral hearing loss:
- Hearing loss that runs in the family
- A problem with the outer, middle, or inner ear
- Some syndromes
- Illnesses or infections
- Exposure to loud sounds
- Traumatic brain injury (TBI)
Sudden sensorineural hearing loss, which NIDCD notes (last updated September 14, 2018) frequently affects only one ear, is one cause of unilateral hearing loss. For detailed guidance on sudden hearing loss urgency, see our sudden hearing loss emergency guide.
Meniere's disease usually affects only one ear, according to NIDCD (last updated August 15, 2024).
Vestibular schwannoma (acoustic neuroma) is a benign tumor that usually causes unilateral or asymmetric hearing loss, tinnitus, and dizziness. NIDCD (last updated March 6, 2017) states that as the vestibular schwannoma grows, it affects the hearing and balance nerves, usually causing unilateral or asymmetric hearing loss, tinnitus, and dizziness or loss of balance. NIDCD emphasizes that the important point is that unilateral or asymmetric symptoms are the worrisome ones.
For single-sided deafness specifically, the Journal of Clinical Medicine review lists cochleovestibular abnormalities, temporal bone trauma, Meniere's disease, vestibular schwannoma, vascular ischemia, autoimmune disorders, and infections as etiologies. The review notes that SSD is commonly idiopathic in nature, and often, this loss can be sudden in onset.
How unilateral hearing loss is evaluated
ASHA says an audiologist can help if you or someone you know is experiencing hearing difficulties.
For sudden hearing loss, the American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNS) published a clinical practice guideline in August 2019 (Otolaryngology-Head and Neck Surgery, August 2019). The guideline's key action statements describe that clinicians should distinguish sensorineural hearing loss from conductive hearing loss when a patient first presents with sudden hearing loss. Clinicians should obtain, or refer to a clinician who can obtain, audiometry as soon as possible, within 14 days of symptom onset. Clinicians should evaluate patients with sudden sensorineural hearing loss for retrocochlear pathology by obtaining magnetic resonance imaging (MRI) or auditory brainstem response (ABR).
For sudden one-sided hearing loss, NIDCD notes that if sudden hearing loss occurs only in one ear, tumors on the auditory nerve should be ruled out as the cause. NIDCD adds that magnetic resonance imaging (MRI) scans are critical in the early detection of a vestibular schwannoma.
FDA's consumer page on over-the-counter hearing aids (content current as of May 3, 2023) lists conditions that warrant seeing a doctor, preferably an ear-nose-throat doctor (an ENT), before using an OTC hearing aid. Those include if your hearing changed suddenly in the past 6 months, if you have worse hearing in one ear, and if you hear ringing or buzzing in only one ear.
This page describes unilateral hearing loss and cannot diagnose it. If you have sudden hearing loss, seek medical care immediately. If you have ear pain, drainage, dizziness, or hearing loss after a head injury, contact a physician promptly.
Options in brief (after evaluation)
Treatment depends on the cause and on whether the poorer ear can be aided, which a clinician determines. Options after medical evaluation include:
A CROS system sends sound from the poorer ear to the better ear without surgery; see our Phonak CROS Infinio page for an example.
Bone conduction implants send sound through the skull to the working inner ear and require surgery; see our bone conduction hearing aids guide.
If a clinician says the poorer ear can be aided, our types of hearing aids guide explains the styles.
For single-sided deafness, cochlear implants are an emerging option whose approved uses vary by region; see our hearing aid vs cochlear implant guide.
Rerouting options such as CROS and bone conduction do not restore true two-ear hearing.
Frequently asked questions
What is unilateral hearing loss? +
Unilateral hearing loss is hearing loss in only one ear, with normal hearing in the other ear. It can range from mild to severe.
Is unilateral hearing loss the same as single-sided deafness? +
No. Single-sided deafness is the severe-to-profound, clinically unaidable end of unilateral hearing loss. Unilateral hearing loss also includes milder loss.
What causes hearing loss in one ear? +
Causes include hearing loss that runs in the family; problems with the outer, middle, or inner ear; some syndromes; illnesses or infections; exposure to loud sounds; traumatic brain injury; sudden sensorineural hearing loss; Meniere's disease; and a benign tumor on the hearing nerve such as vestibular schwannoma.
Is sudden hearing loss in one ear an emergency? +
Yes. NIDCD and NIA say to treat sudden hearing loss as a medical emergency and see a doctor immediately. Delaying diagnosis and treatment can make treatment less effective. Read our sudden hearing loss emergency guide for what to do next.
Why might a doctor order an MRI for hearing loss in one ear? +
One-sided hearing loss can be an early sign of a vestibular schwannoma, a benign tumor on the hearing nerve, and MRI is critical in detecting one early. For sudden hearing loss, the AAO-HNS guideline calls for MRI or ABR to check for retrocochlear causes.
Can I use an OTC hearing aid for hearing loss in one ear? +
FDA's consumer guidance says to see a doctor, preferably an ENT, first if one ear hears worse than the other.
How is unilateral hearing loss treated? +
That depends on the cause and on whether the poorer ear can be aided, which a clinician determines. Options after evaluation include CROS systems, bone conduction implants, and, for single-sided deafness, cochlear implants.
Only after medical evaluation
If a clinician says the poorer ear can be aided, learn about hearing aid styles.
Explore hearing aid types →Medical evaluation comes first
Sources
- American Speech-Language-Hearing Association (ASHA), Types of Hearing Loss. Last Reviewed: May 1, 2026. Accessed November 5, 2026.
- Snapp HA, Ausili SA. Hearing with One Ear: Consequences and Treatments for Profound Unilateral Hearing Loss. J Clin Med. 2020 Apr 3;9(4):1010. PMC7230949. Accessed November 5, 2026.
- National Institute on Deafness and Other Communication Disorders (NIDCD), Sudden Deafness (Sudden Sensorineural Hearing Loss). Last Updated Date: September 14, 2018. Accessed November 5, 2026.
- National Institute on Aging (NIA), Hearing Loss: A Common Problem for Older Adults. Content reviewed: January 19, 2023. Accessed November 5, 2026.
- National Institute on Deafness and Other Communication Disorders (NIDCD), Meniere's Disease. Last Updated Date: August 15, 2024. Accessed November 5, 2026.
- National Institute on Deafness and Other Communication Disorders (NIDCD), Vestibular Schwannoma (Acoustic Neuroma) and Neurofibromatosis. Last Updated Date: March 6, 2017. Accessed November 5, 2026.
- Chandrasekhar SS, et al., American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNSF). Clinical Practice Guideline: Sudden Hearing Loss (Update). This guideline was published in the August 2019 issue of Otolaryngology-Head and Neck Surgery on August 1. Accessed November 5, 2026.
- U.S. Food and Drug Administration, OTC Hearing Aids: What You Should Know. Content current as of: 05/03/2023. Accessed November 5, 2026.
- National Institute on Deafness and Other Communication Disorders (NIDCD), Hearing Aids. Last Updated Date: October 11, 2022. Accessed November 5, 2026.
- U.S. Food and Drug Administration, Other Products and Devices to Improve Hearing. Content current as of: 11/18/2022. Accessed November 5, 2026.