What should you know about cold and flu for high blood pressure?

Fever, sweating, reduced drinking and vomiting can leave you dehydrated, which may make you feel weak or light-headed and can change how your blood-pressure treatment affects you. A blocked nose may tempt you to use an oral decongestant, but ingredients such as pseudoephedrine can narrow blood vessels and raise blood pressure. Combination products may also duplicate pain-relief ingredients or contain stimulants.

Read the active ingredients rather than relying on the product name. Your usual blood-pressure readings may change during illness, so a single reading should be interpreted alongside how you feel and which medicines you have taken.

Rest, drink regularly unless a clinician has asked you to restrict fluids, and use simple measures such as saline nasal spray, warm drinks and humidified air for comfort. Ask a pharmacist or clinician to check any cold remedy against your blood-pressure medicines before taking it. Do not stop prescribed treatment because of a cold without advice, and do not share antibiotics or use leftover medicines.

Keep a record of your blood-pressure readings, temperature, symptoms and non-prescription medicines. If you have kidney disease, heart failure, or another long-term condition, seek tailored advice before using ibuprofen or similar anti-inflammatory painkillers.

Seek urgent help for chest pressure, severe breathlessness, fainting, new weakness on one side, trouble speaking, confusion, or a sudden severe headache. Contact a clinician promptly if you cannot keep fluids down, are passing very little urine, symptoms are worsening, or your blood-pressure readings are repeatedly much higher than your advised range with symptoms.

Which ingredients should I avoid with my blood-pressure medicines? What can I use for congestion, fever or aches? Should I check my blood pressure more often while ill, and what reading or symptom means I should call?