Flu cases are continunig to soar across Northern Ireland
13:00, 15 Dec 2025Updated 16:15, 15 Dec 2025
A pharmacist has issued a warning to those using weight loss injections(Image: Matthew Horwood/Getty Images)
Pharmacists are urging people using weight loss injections to be alert to signs of dehydration as flu cases rise, warning that the combination of illness and appetite-suppressing medication could increase health risks.
Experts say growing numbers of patients are now experiencing flu season while taking drugs such as Mounjaro or Wegovy for the first time, which can make it harder to distinguish between medication side effects and symptoms of a viral infection.
They are advising users to prioritise recovery, monitor their fluid and food intake closely and seek professional advice if they are unsure whether to continue their injections while unwell.
Jason Murphy, Head of Pharmacy and weight loss expert at Chemist4U, told RSVP Live : “With thousands already estimated to have the flu and more people than ever on weight loss injections, many may be facing flu season while on their medication for the first time.
“While some common side effects of weight loss injections, like headache, fatigue and nausea resemble flu symptoms, these are usually temporary and subside within a few days to a few weeks.”
However, he said it was important for users to understand the distinction between the two.
“It’s important to understand the difference: Weight loss injection side effects are caused by the medication and mainly affect the digestive system, blood sugar and other bodily functions, whereas flu symptoms are caused by a viral infection and primarily affect the respiratory system. Understanding the difference can help people manage their symptoms safely”, he revealed.
Jason Murphy also advised people to reconsider their dosing schedule if illness affects their ability to eat.
“If you start to feel unwell and your illness makes it difficult to eat three meals per day, or it’s generally impacting your appetite, you may wish to delay a dose until full recovery”, he noted.
“This is suggested to minimise the risk of malnutrition and dehydration. If you’re unable to eat or drink normally, taking a medication that reduces appetite, like Mounjaro or Wegovy, could make flu recovery more difficult. Without adequate food and liquids, you won’t be getting the vitamins and nutrients your body needs to fight off an infection.”
He stressed that hydration was particularly important. “Staying hydrated is crucial on medications like Mounjaro and Wegovy, especially while ill.”
Jason outlined warning signs that the body may be becoming dehydrated.
“Proper hydration supports digestion and blood sugar control, while helping to prevent constipation. During flu season, dehydration can worsen medication side effects and flu symptoms. Some known warning signs include darker yellow urine, dry mouth and mild headaches, but people are not successful at spotting other signs like harder-than-usual bowel movements and unusual tiredness. It’s beneficial to consider adding an electrolyte drink or rehydration solution to help boost fluid intake and maintain hydration, particularly during this time of year.
“While experiencing the flu, it’s also recommended to rest and sleep, keep warm, and take paracetamol or ibuprofen to lower your temperature and treat aches and pains.
“By paying attention to flu symptoms (high temperatures, aching body, dry cough, sore throat, loss of appetite, etc.), following the above steps can help you get better quicker and back to your usual dosing. If you have concerns about managing your medication during illness, consult with your prescriber, doctor or pharmacist for personalised guidance.”
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