Medicines before surgery and anaesthesia: what to tell the pre-assessment team

An anaesthetic changes how the heart, lungs, blood vessels and gut behave for a few hours, and the drugs the anaesthetist chooses interact with what you already take. The pre-operative assessment exists to find those interactions early, when there is time to adjust the plan, rather than on the morning of surgery.

The NHS describes this appointment as happening a few weeks before the procedure, to make sure you are fit for treatment. It may include blood tests, X-rays and an ECG, and long-term conditions such as diabetes, high blood pressure or anaemia are ideally as well managed as possible beforehand.

Bring the actual boxes, or a printed repeat-prescription list, rather than relying on memory. A named list that includes the dose and timing is more useful than a description such as "a small white tablet for my blood pressure".

• Prescription medicines, including inhalers, patches, injections, eye drops and creams.

• Medicines bought without a prescription: painkillers, antacids, sleeping aids, antihistamines.

• Vitamins, herbal remedies and traditional medicines, whatever their source.

• Recreational drugs and alcohol use, which the team asks about in confidence because they affect anaesthetic drugs.

• Allergies and previous problems with anaesthetics, in you or in blood relatives.

Not every medicine needs to change, and the advice depends on the operation, the type of anaesthetic and the local hospital protocol. The groups below are those clinicians commonly think about; the decision is individual.

• Blood thinners and antiplatelet tablets: balancing bleeding risk against clot risk, which may mean pausing, bridging or continuing.

• Diabetes medicines and insulin: dose changes during fasting, with close sugar checks.

• Blood pressure and heart medicines: many are continued, a few may be held on the morning of surgery.

• Immunosuppressants: the NHS azathioprine pages say to tell the doctor or anaesthetist before any procedure.

• Parkinson's medicines: the NHS co-beneldopa page says you may need to stop it before a general anaesthetic, so the team plans around the timing.

• Hormone treatments and some pain or mood medicines.

Cancer Research UK notes that herbal medicines can interfere with treatment, and that Asian ginseng and bilberry can increase bleeding risk during surgery. It also warns that some unlicensed herbal products have been found to contain ingredients not listed on the label.

Because of that, the team prefers to know about everything. There is rarely a judgement attached. A product that is harmless in itself may still change how a drug is processed or how blood clots, and a short pause before surgery is often all that is needed.

You receive written instructions on when to stop eating and drinking, and which morning medicines to take with a sip of water. The NHS notes that additional medicines may be given before the main anaesthetic to help you relax, reduce stomach acid, prevent sickness or help with pain.

If you are unsure whether to take a particular tablet on the morning, ring the pre-assessment nurse rather than guessing. Equally, if you become unwell with a cough, cold, fever or sickness before the date, call the hospital; a short delay can be safer.

The team restarts medicines as soon as it is safe, and sometimes changes the dose. Take the discharge medicines list seriously: it names what to resume, what to stop and what is new, such as painkillers or blood-thinning injections. If your list does not match the tablets in the cupboard, ask the pharmacist or GP to reconcile it.

Common anaesthetic side effects described by the NHS include thirst, drowsiness, a hoarse voice, shivering, nausea and brief confusion, usually passing within minutes to hours. Serious complications are rare. Further guidance appears in the existing pages on general, local, spinal and epidural anaesthetic.