Giardia symptoms, testing and when to see a GP

A rise in reported giardia cases is a reason to take persistent diarrhoea seriously, but it does not mean that every tummy upset is giardiasis. Most short-lived diarrhoea settles within a few days. If symptoms continue, especially with bloating, foul-smelling diarrhoea, swimming exposure, close contact with someone unwell or possible exposure to contaminated water, a GP may need to arrange a stool test.

The UK Health Security Agency reported 6,069 laboratory-confirmed cases in England in 2025, an increase of 11.4% from 2024 and the highest annual figure since 2016. Giardia can be caught in the UK as well as abroad.

What are the symptoms of giardia?

Giardiasis is an intestinal infection caused by a microscopic parasite. The main symptom is usually diarrhoea, which may be particularly unpleasant or foul-smelling.

According to NHS guidance on giardiasis, other common symptoms including

• abdominal pain or cramps
• bloating and excessive wind
• foul-smelling or eggy burps
• weight loss

Some people carry and spread the parasite without having symptoms themselves. Symptoms may begin several days or weeks after exposure, and UKHSA guidance gives an incubation period of 5 to 25 days. This means the connection with swimming, water exposure or another source may not be immediately obvious.

Unlike many brief stomach bugs, giardiasis can continue for weeks and sometimes longer if it is not identified and treated. Young children, older people and those with weakened immune systems may be more vulnerable to dehydration and other complications.

How do people catch it?

Giardia spreads when tiny traces of infected faeces reach another person's mouth. Possible routes include

• drinking untreated or contaminated water
• eating food washed in contaminated water or handled by an infected person
• swallowing water while swimming in a pool, lake, river or the sea
• close contact with an infected person, including within a household or childcare setting
• contact with infected animals
• sexual contact involving exposure to faeces

Recent overseas travel is an important clue, but it should not be treated as essential. UKHSA confirms that infections are also acquired within the UK.

When speaking to a doctor, mention recent travel, open-water swimming, camping, contact with someone who has diarrhoea and whether anyone else in your household is unwell. The timing of these events can help the doctor decide which tests are appropriate.

How is giardia tested?

A GP will usually ask about your symptoms and possible exposures. They may arrange for a sample of your poo to be sent to a laboratory to look for giardia or another cause of infection.

Giardia is normally investigated through a stool sample, not a routine blood test. Blood tests may sometimes be appropriate if a doctor wants to assess the effects of prolonged illness or look for other explanations, such as coeliac disease, but they do not replace infection testing.

Do not assume that persistent symptoms are IBS without an assessment. The NHS explains that stool tests may be used to rule out infections when investigating possible IBS.

If giardiasis is confirmed or strongly suspected, it is usually treated with prescription antimicrobial medicine. A clinician must decide which treatment is suitable after considering factors such as age, pregnancy, other conditions and current medicines. People living with you may sometimes need testing or treatment as well.

Return to a GP if symptoms have not improved a week after starting treatment, as the NHS advises that further treatment or specialist assessment may be needed.

Giardia or IBS and how to tell the difference

Giardiasis and irritable bowel syndrome can both cause cramps, bloating, wind and diarrhoea. Symptoms alone may not provide a reliable answer, but the overall pattern can offer clues.

Giardia is more likely to present as a new illness, particularly after a relevant exposure. Diarrhoea, foul-smelling burps and weight loss may be prominent, and the infection can spread to other people.

IBS is not an infection. Its symptoms tend to come and go over time and may include constipation as well as diarrhoea. Typical IBS pain is often worse after eating and improves after doing a poo. Food, caffeine, alcohol and stress can trigger flare-ups.

A gastrointestinal infection can sometimes be followed by longer-lasting IBS-type symptoms. If diarrhoea or bloating continues after an infection has been treated, a GP can consider whether further stool tests, blood tests or another assessment are needed.

When should you see a GP?

Seek an urgent GP appointment or contact NHS 111 if

• diarrhoea has lasted for more than seven days
• you have bloody diarrhoea or bleeding from your bottom
• you cannot keep fluids down
• you have signs of dehydration despite drinking or using oral rehydration solution
• you are losing weight without trying
• the symptoms are worsening rather than improving

UKHSA specifically advises parents to contact a GP or NHS 111 if a child has dehydration, worsening diarrhoea or diarrhoea lasting more than three days. It is sensible to seek advice sooner for a young child, an older person or someone with a weakened immune system.

Signs of dehydration include passing less urine, dark urine, a dry mouth, dizziness, unusual tiredness and a fast heart rate. Get urgent help from NHS 111 if these develop. The NHS dehydration guidance advises calling 999 or going to A&E if someone becomes confused, difficult to wake, cold or blotchy, or has serious difficulty breathing.

Sudden severe abdominal pain or being too unwell to drink also requires urgent assessment rather than waiting for a routine appointment.

What can you do while waiting for advice or results?

Preventing dehydration is the immediate priority. Drink regularly, taking small sips if you feel sick. A pharmacist can recommend oral rehydration sachets, which replace some of the salts and sugars lost through diarrhoea.

To reduce the risk of passing the infection to others

• wash your hands thoroughly with soap and water after using the toilet, changing nappies and before handling food
• clean toilet seats, flush handles, taps and frequently touched bathroom surfaces
• wash contaminated towels, clothes and bedding separately on a hot wash
• avoid preparing food for other people where possible
• do not share towels, flannels, cutlery or utensils
• stay away from work, school or nursery until diarrhoea has stopped for at least 48 hours
• do not use a swimming pool until two weeks after symptoms have stopped

If you handle food at work, tell your employer promptly and follow workplace or public-health advice before returning.

Getting assessed privately

Your NHS GP is an appropriate first route for persistent diarrhoea, and NHS 111 should be used when symptoms require urgent advice. A pharmacist can help with oral rehydration and straightforward self-care questions.

If timely private assessment is more convenient, DocTap offers same-day private GP appointments, subject to availability, in London clinics as well as video consultations across the UK. For ongoing diarrhoea, an in-person appointment may be preferable if an abdominal examination or physical sample is likely to be needed. A GP can review the pattern of symptoms and advise how appropriate stool testing, other investigations or onward care should be arranged.

Booking a broad blood-test panel alone is not the best way to investigate possible giardia. Where blood tests may be useful, testing with GP review helps ensure they are selected and interpreted in the context of your symptoms. Urgent symptoms, significant dehydration or severe pain should still be directed to NHS 111, urgent care or A&E as appropriate.