Most ordinary mouth ulcers heal within one or two weeks. Arrange a dentist or GP assessment if an ulcer lasts longer than three weeks, looks different from your usual ulcers, bleeds or becomes increasingly red and painful. Recurrent ulcers can follow local irritation, stress or other triggers, but persistent symptoms deserve an explanation rather than another tube of gel. [1]
An ulcer can make lunch, coffee and conversation uncomfortable. If it keeps returning, it is reasonable to ask whether something is causing it. The useful distinction is between separate ulcers that heal and recur, and one sore that has never properly gone away.
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Start with the timeline
Write down when the current ulcer appeared and whether the previous one healed fully. NHS guidance sets a clear threshold: an ulcer lasting more than three weeks should be checked by a dentist or GP. Most ulcers are harmless, but a long-lasting ulcer can sometimes be a sign of mouth cancer. Do not keep restarting the clock because the pain has changed. [1]
An ulcer that is unusually large, near the back of the throat, bleeding or becoming more painful also warrants assessment. Mention ulcers elsewhere on the body or painful, red or swollen joints. Those features change the questions a clinician needs to ask. [1]
Why do mouth ulcers come back?
Common possibilities include biting the cheek, a sharp tooth or rough filling, poorly fitting dentures, damage from a toothbrush, hot food or a product that irritates the mouth. Tiredness, stress and anxiety can also be associated with episodes. A dentist is particularly useful when a sharp edge or appliance keeps rubbing the same place. [1]
Sometimes the wider history matters. NHS guidance lists some vitamin or mineral deficiencies, certain medicines, coeliac disease and Crohn's disease among possible associations. That does not mean every recurrent ulcer requires an extensive blood panel or indicates a digestive disease. It means the pattern, associated symptoms and examination should guide the next step. [1]
Tell the clinician what you take, including prescribed medicines and supplements. Do not stop a regular medicine because you have read that it might be associated with ulcers.
What can help an uncomplicated ulcer?
There is no instant cure, but reducing irritation can make eating and drinking more comfortable. NHS advice includes a soft toothbrush, softer foods and avoiding very hot, spicy, salty, acidic or rough foods while the ulcer heals. [1]
A pharmacist can advise on suitable pain relief, mouthwashes or other products. One simple option described by the NHS is a saline rinse: dissolve half a teaspoon of salt in a glass of warm water, rinse and spit it out. Do not swallow the solution. Ask a pharmacist about suitability if the advice is for a child or you have additional health concerns. [1]
The aim is relief while healing occurs, not covering symptoms indefinitely. If a sore has reached the three-week point, book an assessment even if a product makes it less painful.
When is a GP useful, and when is a dentist better?
A dentist can examine a persistent sore and check for a local cause such as a sharp tooth or denture problem. A GP can review recurrent episodes, medicines and symptoms elsewhere in the body and decide whether tests or referral are appropriate. Either route is better than repeatedly treating an unexplained persistent ulcer at home. [1]
Ask The Online GP about an appropriate appointment . If a hands-on mouth examination or dental assessment is needed, an online consultation is not a replacement for it. The doctor's role is to help choose the safe next step, not promise a diagnosis from a photograph.
Prepare for the appointment
A short record helps you use the consultation well:
The date the current ulcer appeared and whether it is healing.
Whether ulcers recur in the same spot or different places.
A clear photograph if the appearance changes between episodes.
Any sharp tooth, dental work, braces or dentures near the sore.
Medicines, supplements and products you have tried.
Other symptoms, including ulcers elsewhere, joint symptoms or digestive problems.
Ask whether the ulcer needs an in-person examination, what the likely explanation is and when to return if it has not healed. Do not assume an antibiotic is the answer: treatment depends on the cause and findings. [1]
How much is a private online GP consultation?
The Online GP offers a telephone consultation for £59, up to 15 minutes , or a video consultation from £150, up to 30 minutes . Availability is confirmed before booking. Any prescription, referral or further investigation depends on clinical assessment; ask about separate costs before proceeding. [2]
See the consultation options , call 020 3951 3429 , or email team@thewellnesslondon.com . Do not delay a needed dental or in-person assessment while waiting for an email.
Common questions
Are mouth ulcers contagious?
Ordinary mouth ulcers are not contagious. They are different from cold sores, which often begin with tingling or burning on or around the lips. A clinician can assess an uncertain lesion. [1]
Does a mouth ulcer mean I have a vitamin deficiency?
Not necessarily. Deficiency is one possible association among several. Testing should be based on the history and examination rather than assumed from a single ulcer. [1]
Should I wait three weeks before getting help?
No. Three weeks is the threshold for a persistent ulcer, not a rule to ignore earlier concerns. An unusual ulcer, bleeding, increasing pain or associated symptoms can justify an earlier appointment. [1]
Can an online doctor prescribe treatment?
Where appropriate, a doctor can discuss treatment and arrange a prescription or referral. This is not guaranteed, and an in-person or dental examination may be necessary. [2]
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Sources
The Online GP: consultation options and current fees .
The Wellness Clinical Team. Sources checked 16 October 2026. General information, not an individual diagnosis or treatment plan.