Why Your Medication List Matters

Hip and knee replacement surgery is well-tolerated by most patients, but every medication you take has the potential to affect how the operation, the anaesthetic, and your recovery unfold. Some increase bleeding during surgery. Some interact with anaesthetic drugs. Some affect your immune system and infection risk. A few have specific concerns that have only emerged in the last year or two as new medications have come into use.

The good news is that almost none of these issues require dramatic action on your part. The pre-operative assessment process exists precisely to review every medication you take and give you a personalised plan. This article explains the main categories that need that review, so you know what to expect and what to bring to the discussion.

The single most important rule

Do not stop or change any medication before surgery without being told to do so by your surgeon, anaesthetist or pre-operative team. Stopping certain medications without supervision can be more dangerous than the surgery itself. Equally, do not assume something is safe to continue just because nobody has told you to stop it. The safe approach is always to discuss your full list at your pre-operative assessment.

Bring Everything to Your Pre-Operative Assessment

When you attend your pre-operative assessment clinic, the team will ask about your medications. To make this useful, bring a complete list of:

  • All prescription medications, with the dose and how often you take them
  • All medicines you buy without prescription, including painkillers and indigestion remedies
  • Any vitamins, herbal supplements or "natural" remedies, even if you do not consider them medicines
  • Any injectable treatments such as biologics, immunotherapy or weight-loss injections
  • Any recent or planned changes to any of the above

Patients often forget to mention things they take "every now and then" or items bought from health food shops. Several of the most clinically important pre-operative concerns sit in exactly those categories, so do not edit your list before sharing it.

Blood Thinners and Antiplatelet Medications

This is the category most likely to need active management before surgery. Blood thinners include warfarin, the newer direct oral anticoagulants such as rivaroxaban, apixaban, dabigatran and edoxaban, and antiplatelet drugs such as clopidogrel, ticagrelor and prasugrel. Aspirin sits in a related but separate category.

Continuing these medications through surgery would significantly increase bleeding during the operation. But stopping them carries its own risks: patients on these drugs typically take them to reduce the risk of stroke, heart attack, or recurrent blood clot. Stopping abruptly without a plan can be dangerous.

The pre-operative team and, where relevant, your cardiologist or haematologist will produce an individualised plan that balances both risks. This often involves stopping the medication a specific number of days before surgery and restarting it shortly afterwards. Some patients need a temporary "bridging" injection during the gap. The exact plan depends on the drug, the dose, the reason you are taking it, and the type of surgery.

Anti-Inflammatory Painkillers (NSAIDs) and Aspirin

Non-steroidal anti-inflammatory drugs are some of the most commonly used painkillers. They include ibuprofen (Nurofen, Brufen), naproxen, diclofenac, and meloxicam, among others. Many patients with hip or knee arthritis take them daily without thinking of them as "medication."

NSAIDs increase bleeding by reducing platelet function, and they can affect kidney function around the time of surgery. The usual pre-operative advice is to stop them roughly a week before the operation, although the exact timing depends on the drug. Paracetamol is generally considered a safer alternative for pre-operative pain control.

Low-dose aspirin taken for heart protection is treated separately from NSAIDs and should not be stopped without specific advice. Aspirin used occasionally for headaches, however, follows the same logic as other NSAIDs.

Diabetes Medications

Diabetes medications need careful peri-operative review for two reasons: the risk of low blood sugar while you are fasting before surgery, and concerns specific to certain newer drug classes.

Insulin doses usually need adjustment on the day of surgery. Metformin is generally continued, although there are specific situations where it is held briefly. The newer SGLT2 inhibitors (such as dapagliflozin, empagliflozin, canagliflozin) have a recognised risk of a serious complication called euglycaemic ketoacidosis around the time of surgery, and current UK guidance recommends stopping them three days before any planned operation.

GLP-1 Receptor Agonists (Ozempic, Wegovy, Mounjaro and Similar)

This category has become much more relevant in the past two years. GLP-1 receptor agonists are used to treat type 2 diabetes (semaglutide as Ozempic, dulaglutide as Trulicity, liraglutide as Victoza) and increasingly for weight management (semaglutide as Wegovy, tirzepatide as Mounjaro).

The concern is that these medications slow how quickly the stomach empties. This can mean food remains in the stomach longer than expected, even after the standard fasting period before surgery. Under anaesthetic, retained stomach contents can cause aspiration into the lungs, which is a serious complication.

The current 2025 UK consensus from the Association of Anaesthetists and Royal College of Anaesthetists takes an individualised approach. For most patients, the recommendation is now to continue GLP-1 medications and have an open discussion with the anaesthetic team, who may modify the fasting plan or use specific techniques during induction. For some patients, a temporary pause may be advised. This is a fast-moving area of practice, so the answer for your situation should come directly from the anaesthetist who will look after you.

If you take a GLP-1 for any reason

Always tell the pre-operative team and the anaesthetist. This applies whether you take it for diabetes, weight loss, or both. Do not stop the medication on your own initiative; the safe and appropriate plan will be made for you, and current guidance often favours continuation rather than withdrawal.

Long-Term Steroids

Patients who take oral steroids such as prednisolone for conditions like rheumatoid arthritis, polymyalgia rheumatica, or asthma need careful peri-operative management. The body's natural stress response to surgery normally involves a surge in cortisol, but long-term steroid use suppresses this. Without supplementation, this can cause low blood pressure and other problems during and after the operation.

The plan is rarely to stop the steroid. More commonly, the dose is temporarily increased to cover the surgical period, then returned to normal afterwards. Inhaled steroids for asthma usually continue without change. Topical steroid creams have a much smaller systemic effect and rarely need adjustment.

Biologics, Immunotherapy and Disease-Modifying Treatments

This is an increasingly important category. Many patients now take biologic drugs or immunotherapy treatments for conditions such as rheumatoid arthritis, psoriasis, inflammatory bowel disease, or cancer. Examples include adalimumab (Humira), etanercept, infliximab, rituximab, methotrexate, and a range of cancer immunotherapies including pembrolizumab and nivolumab.

These medications can affect the immune system in ways that influence wound healing and infection risk after surgery. Many of them have specific recommendations about timing the surgery in relation to the most recent dose. For some, the operation is timed to fall just before the next scheduled dose, allowing the drug to be at its lowest level during healing. For others, no change is needed.

The right plan depends on the specific drug, your underlying condition, and the type of surgery. It usually requires a conversation between the orthopaedic team and the consultant who prescribes the immunotherapy. Bring the full prescription details (drug, dose, when you last had it, when the next is due) to your pre-operative assessment so that conversation can take place in good time.

Herbal Supplements and "Natural" Remedies

This is the category patients most often forget to mention, on the assumption that "natural" means "safe." Several common herbal supplements have meaningful effects on bleeding and anaesthetic interactions:

  • Garlic, ginger, ginkgo and ginseng can all increase bleeding
  • St John's Wort interacts with many anaesthetic and post-operative drugs
  • High-dose fish oil and turmeric supplements can affect platelet function
  • Valerian and kava may interact with anaesthetic agents

Most herbal supplements are stopped one to two weeks before surgery. Vitamins are generally less of a concern, but high-dose vitamin E in particular can affect bleeding and is usually paused.

Smoking, Alcohol, Cannabis and Other Substances

These are not medications in the conventional sense, but they affect surgery in ways that the team needs to know about. Smoking significantly impairs wound healing and increases infection risk after joint surgery; even cutting down for a few weeks before the operation makes a measurable difference. Heavy alcohol use can affect anaesthetic drug doses and post-operative recovery. Recreational cannabis and other substances can interact with anaesthetic agents and affect post-operative pain control.

Whatever you use, telling the team is the right thing to do. The conversation is confidential, the team is not there to judge, and accurate information leads to a safer operation.

"There is no medication, supplement, or substance that is too embarrassing to mention. The risks of getting this wrong are far greater than the awkwardness of asking. The pre-operative team and the anaesthetist will give you the right plan; their job is much harder if the list is incomplete."

Mr Shakir Hussain, Consultant Orthopaedic Surgeon

What Happens at Your Pre-Operative Assessment

At the pre-operative assessment clinic, a specialist nurse will go through your full medication list with you. Where there are issues, the plan may be made there and then, or it may be referred to the anaesthetist or to the consultant who prescribed a specific drug. Complex cases (multiple blood thinners, ongoing immunotherapy, recent cardiac procedures) may need a few weeks of co-ordination, which is why pre-operative assessments are usually scheduled several weeks before surgery.

You will leave the clinic with a clear written plan: which medications to continue normally, which to stop and when, and which doses to take on the morning of surgery. If you are unclear about anything, ask before you leave. If something feels unclear later, telephone the pre-operative team rather than guess.

Bring Your List to Your Consultation

You can also bring your medication list to your consultation with Mr Hussain. The decision to operate is based on your overall fitness as much as on the state of your hip or knee, and your medications are a meaningful part of that picture. If a particular drug or treatment has implications for the timing of surgery, it is much better to identify that at the consultation stage than at the pre-operative assessment a few weeks before the operation.