Everything you need to know about Doxycycline and its side effects

DoktorABC editorial team

Accurate, up-to-date health information written by our editorial team and reviewed by UK-registered prescribers.

How common are doxycycline side effects?

Doxycycline is generally well tolerated at the doses used for conditions such as chlamydia, where a seven-day course of 100 mg twice daily is the standard treatment. The majority of people who take it complete their course without significant problems.

Side effects, when they do occur, are most commonly gastrointestinal in nature and tend to be mild to moderate. They are most noticeable in the first few days of treatment and often improve as the course continues.

The frequency categories used below are consistent with MHRA labelling conventions and are based on the UK patient information leaflet for doxycycline 100 mg capsules (Sovereign Medical, medicines.org.uk, last updated March 2026).

Common gastrointestinal  side effects

Gastrointestinal side effects are the most frequently reported with doxycycline and are a direct result of the antibiotic's effect on the digestive system.

• Nausea and vomiting: Nausea is one of the most commonly reported side effects. It is more likely when doxycycline is taken on an empty stomach. Taking it with food significantly reduces the likelihood of nausea for most people.
• Diarrhoea: Changes to bowel habits are common with antibiotics generally, as doxycycline affects the balance of bacteria in the gut. Mild diarrhoea during a short course is usually self-limiting and resolves once treatment ends.
• Stomach pain and indigestion: Abdominal discomfort and heartburn can occur, most commonly when doxycycline is taken without food.
• Glossitis and oral effects: Inflammation of the tongue and oral thrush (candidiasis) can occur, particularly with longer courses. If you notice a sore or coated tongue, or develop oral thrush symptoms, contact your prescriber.

Photosensitivity and protecting your skin during treatment

Photosensitivity, an increased sensitivity of the skin to sunlight and UV light, is a well-recognised side effect of doxycycline.

This means that exposure to sunlight or UV sources such as sunbeds can cause the skin to burn more quickly and more severely than usual. The reaction can affect areas of skin not normally prone to burning and can occur even on cloudy days.

Practical steps to reduce the risk during your course:

• Apply a broad-spectrum sunscreen with an SPF of at least 30 to exposed skin before going outdoors
• Wear protective clothing, including long sleeves and a hat where practical
• Avoid sunbeds and prolonged sun exposure for the duration of treatment
• Be aware that the increased sensitivity may persist briefly after finishing the course

How oesophageal irritation can occur when taking doxycycline 

Oesophageal irritation is a less common but important side effect that is largely preventable with correct administration. If doxycycline capsules or tablets remain in contact with the lining of the oesophagus (the tube connecting the throat to the stomach), they can cause local irritation, inflammation, and in rare cases, ulceration.

Risk of oesophageal irritation can be reduced by taking doxycycline tablets at least one hour before bedtime, to avoid lying down during or after taking the dose, and with a meal and a large glass of water.

Symptoms of oesophageal irritation include a burning sensation in the chest, pain or difficulty when swallowing, or a feeling that the capsule is stuck. If you experience significant chest pain or difficulty swallowing after taking doxycycline, contact your prescriber or pharmacist promptly.

To reduce the risk:

• Take each dose with a full glass of water (at least 200 ml)
• Remain upright for at least 30 minutes after taking the dose
• Do not take doxycycline immediately before lying down or going to sleep

Why doxycycline is not given to young children

The use of drugs of the tetracycline class during tooth development, which includes the last half of pregnancy, infancy, and childhood up to the age of 8 years, may cause permanent discolouration of the teeth (yellow-grey-brown). This adverse reaction is more common during long-term use but has been observed following repeated short-term courses.

This is why doxycycline is not routinely prescribed to children under 8 years of age, and why it is contraindicated during pregnancy and in breastfeeding mothers. If you have any questions about doxycycline use in relation to pregnancy or a child, speak to a healthcare professional.

Less common side effects

The following side effects are reported less frequently but are worth being aware of.

• Skin rash: A mild skin rash can occur and is usually not serious, but any rash developing during a course of doxycycline should be reported to your prescriber, as it can occasionally be the first sign of a more significant reaction.
• Vaginal or oral thrush: Antibiotics can disrupt the natural balance of microorganisms in the body, sometimes leading to thrush. If you develop symptoms of thrush during your course, a pharmacist can advise on appropriate treatment.
• Headache: Headaches are reported by some people taking doxycycline, particularly in the early days of treatment.
• Raised intracranial pressure: In rare cases, doxycycline has been associated with raised pressure within the skull (benign intracranial hypertension), which can cause severe headache and visual disturbances. This is rare but warrants urgent medical assessment if it occurs.

Side effects after stopping doxycycline

After finishing a course of doxycycline, side effects should subside. However, for some people, they can persist. Let's look at the possible scenarios for side effects when stopping doxycycline.

• For most people: Common side effects such as nausea, stomach discomfort, and loose stools resolve within a few days of finishing the course as the antibiotic clears the body and the gut microbiome begins to rebalance. Photosensitivity also diminishes once treatment ends, though it is worth continuing sun protection precautions for a short period.
• If gastrointestinal symptoms persist: Mild GI upset that lingers for a few days after finishing is generally not a cause for concern. However, if diarrhoea is severe, contains blood, or persists beyond a week after stopping, contact your GP. Antibiotic-associated diarrhoea caused by Clostridioides difficile (C. diff) is rare with short courses of doxycycline but is worth being aware of.
• If symptoms of the original infection return: Some people ask about symptoms returning after finishing a doxycycline course because they stopped early or missed doses. If a course of doxycycline for chlamydia was not completed in full, the infection may not have been fully cleared. If you are concerned that treatment may not have been completed correctly, contact your prescriber rather than assuming the infection has resolved.

When to seek urgent medical help

The following symptoms require prompt medical attention. Stop taking doxycycline and seek help immediately if you experience any of the following.

Signs of a severe allergic reaction:

• Swelling of the face, lips, tongue, or throat
• Difficulty breathing or swallowing
• Severe skin rash, hives, or widespread redness
• A feeling of faintness or collapse

Severe skin reactions:

• Blistering, peeling, or raw skin
• A rash that is spreading rapidly or accompanied by fever and a sore throat
• Severe sunburn-like reactions

Oesophageal symptoms:

• Severe chest pain or a burning sensation in the chest that does not resolve
• Difficulty swallowing that is getting worse

Other serious symptoms:

• Severe or persistent headache with visual disturbances (possible raised intracranial pressure)
• Yellowing of the skin or eyes (jaundice), which may indicate a liver reaction
• Signs of a significant blood disorder, including unusual bruising, bleeding, or persistent fever

If in doubt, contact NHS 111, your GP, or go to your nearest A&E. Report any suspected serious side effects to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Practical tips to reduce side effects

The following measures can make a meaningful difference to reducing your side effect symptoms.

• Take with food or immediately after a meal to reduce nausea and stomach irritation. Note that dairy products and certain foods can affect absorption (see interactions below) so a non-dairy meal is preferable.
• Use a full glass of water (at least 200 ml) with each dose to reduce the risk of oesophageal irritation.
• Stay upright for at least 30 minutes after taking each dose. Do not take doxycycline immediately before lying down or going to sleep.
• Use sunscreen and protective clothing throughout your course and for a short period afterwards to manage photosensitivity.
• Complete the full course even if symptoms improve before it ends. Stopping early reduces effectiveness and, in the case of infections such as chlamydia, may mean the infection is not fully cleared.

Interactions that can affect side effects or efficacy

Certain substances reduce the absorption of doxycycline into the bloodstream, which can affect how well it works as well as how it is tolerated.

• Antacids: Antacids containing calcium, magnesium, or aluminium can significantly reduce doxycycline absorption. If you need to take an antacid, take it at least two hours before or after your doxycycline dose.
• Dairy products and calcium: Dairy foods and calcium-fortified drinks can reduce doxycycline absorption. While taking doxycycline with a small amount of food is recommended to reduce nausea, taking it with a large glass of milk or a calcium-rich meal should be avoided.
• Iron and zinc supplements: Iron and zinc supplements reduce the absorption of doxycycline. If you take these supplements regularly, take them at a different time of day from your doxycycline dose.
• Alcohol: While alcohol is not contraindicated with doxycycline, it can worsen nausea and stomach irritation, which are already among the most common side effects of the antibiotic. For more detail on doxycycline and alcohol, see our doxycycline and alcohol guide.

Conclusion

Doxycycline is an effective, well-tolerated antibiotic for the large majority of people who take it. The most common side effects, primarily gastrointestinal upset and photosensitivity, are manageable with straightforward practical steps. Knowing what to expect, how to take the medicine correctly, and when to seek help ensures you can complete your course safely and with confidence.

FAQ

The DoktorABC medical advisory board

Dr. Roland Ruiken

Medical advisor, Norway

Dr. Viktor Simunovic

Medical advisor, Croatia

To the medical advisory board