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GuideJuly 2026· 11 min read
Medications before surgery: what has to be paused
Before an operation, almost everyone asks the same, often anxiety-laden question: which medicines do I have to stop, which may I keep taking — and when? The answer depends heavily on the active ingredient and on the procedure. This guide gives you an easy-to-understand overview, but it never replaces the pre-anaesthetic assessment with the anaesthesia team.
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The most important thing firstNever stop or continue medications before an operation on your own initiative. What counts is always the instruction from the pre-anaesthetic assessment. Bring a complete list of your medications to this appointment (including over-the-counter products and food supplements). Blood thinners, diabetes medications and blood-pressure-lowering drugs are especially important.
1. Why some medications are paused
Around an operation, certain medications can increase the risk — above all of bleeding, of circulatory problems under anaesthesia, or of rare metabolic derailments. Other medications, by contrast, have to be deliberately continued, because stopping them would be more dangerous than the procedure itself. The art lies in the individual balance: how high is the bleeding risk of the operation? How high is the risk if the medication is paused?
This weighing-up is done by the treatment team — surgeon, anaesthesia team and often the GP practice or a specialist practice together. Your job is to ensure complete information.
Important to understand: there is no blanket "stop before every operation". One and the same medication can simply continue before a minor procedure and have to be paused before a major operation. It also matters why you take a medicine — a blood thinner after an artificial heart valve is handled differently from one taken purely for prevention. That is why the individual instruction from the pre-op assessment cannot be replaced by anything, not even by this guide.
2. Blood thinners: the most important group
Blood thinners (anticoagulants) are at the centre of every surgical plan because they increase the bleeding risk. When and whether they are paused depends on the active ingredient, on kidney function and on the procedure.
After a stent, NOT on your own — consult cardiology!
Table scrollable to the right
Blood thinners after a stent Anyone taking anticoagulants after a stent implantation must on no account stop them on their own initiative — there is a risk of a life-threatening stent occlusion. Such procedures are closely coordinated with cardiology and, where possible, scheduled only after a protective phase.
Blood thinners safely in view
brite records which anticoagulant you take and when — ready for the pre-op assessment.
Because you have to fast before an operation, diabetes medications can cause low blood sugar (hypoglycaemia) — which is why the dosing is adjusted. At the same time, an operation as stress on the body can also drive blood sugar up. That is why diabetes therapy is closely managed around the procedure and often temporarily changed. Two points are especially important:
Metformin: usually paused on the day of surgery, and for longer with X-ray contrast media — because of kidney function.
SGLT2 inhibitors (Dapagliflozin, Empagliflozin): are usually paused 3–4 days beforehand, because in fasting and stress situations they can trigger a dangerous over-acidification (ketoacidosis) — even with normal blood sugar.
Insulin and sulfonylureas: the dose is adjusted to the fasting state; the exact instruction comes from the treatment team.
4. Blood-pressure and heart medications
Most cardiovascular medications are continued — a sudden stop can be dangerous. But there are subtleties on the morning of surgery:
Beta blockers (e.g. Bisoprolol): as a rule continue — abrupt discontinuation can trigger a racing heart and blood-pressure spikes.
ACE inhibitors and sartans (e.g. Ramipril, Candesartan): are often paused on the morning of surgery, because under anaesthesia they can let blood pressure drop too sharply.
Diuretics (water tablets): frequently withheld on the day of surgery.
5. Other important medications
Beyond blood thinners and diabetes and blood-pressure drugs, there are other preparations that matter for surgical planning. Some quietly increase the bleeding risk, others affect the anaesthesia. So the rule is: better to name one medicine too many than one too few.
NSAID-type painkillers (Ibuprofen, Diclofenac): increase the tendency to bleed and are often paused before larger procedures.
The contraceptive pill / hormone preparations: increase the risk of thrombosis — for larger operations this is discussed individually.
Certain herbal remedies (e.g. St John's wort, ginkgo, high-dose fish oil): can affect clotting and anaesthesia — be sure to state these too.
Thyroid hormones, most psychiatric drugs and antiepileptics: are usually continued — but always according to medical instructions.
In some people with a high thrombosis risk (for example after an artificial heart valve or with certain forms of atrial fibrillation), a paused blood thinner is temporarily bridged with heparin injections — this is called bridging. The goal is to keep the time without full anticoagulation as short and safe as possible. Whether bridging is needed is decided by the treating practice; today it is used less often and more selectively than in the past.
Bridging mainly concerns the older phenprocoumon (Marcumar), which lingers for a long time. With the more modern DOACs, bridging is usually not needed, because their effect wears off quickly and returns just as quickly after the operation. Unnecessary bridging can even increase the bleeding risk — so here too the individual medical decision matters, not a blanket rule.
7. After the operation: don't forget restarting
At least as important as pausing is the question of when each medication is started again — and this is exactly what often gets lost in the bustle after the procedure. For blood thinners, the right moment depends on how well the wound is free of bleeding; too early increases the risk of secondary bleeding, too late the risk of thrombosis and stroke. So already before the operation, or at the latest on discharge, have it put in writing from when you take each paused medicine again. If nothing about this is in the discharge letter, actively ask at the practice rather than deciding yourself.
8. Your checklist before surgery
Create a complete list of medications — including over-the-counter products, vitamins and herbal preparations.
Take it to the pre-anaesthetic assessment and actively ask about each individual medication.
Ask for a written pause plan: what to pause, from when, when to start again?
After the operation, clarify when blood thinners & co. are restarted — this is often forgotten.
How to pause and restart medications safely in general is also covered in the guide Stopping medications.
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That depends on the active ingredient and the procedure. Especially relevant are blood thinners, certain diabetes medications (e.g. SGLT2 inhibitors, Metformin) and, on the morning of surgery, often ACE inhibitors/sartans. Exactly what is paused is determined by the pre-anaesthetic assessment — never decide on your own.
Often yes, but not always. DOACs are usually paused 1–2 days beforehand, phenprocoumon (Marcumar) around 7–10 days beforehand, sometimes with heparin bridging. ASA is continued or not depending on the situation. After a stent, anticoagulants must on no account be stopped on your own initiative.
Beta blockers are usually continued. ACE inhibitors and sartans, by contrast, are frequently paused on the morning of surgery, because under anaesthesia they can lower blood pressure too much. You get the specific instruction at the pre-anaesthetic assessment — follow it exactly.
Metformin is usually paused on the day of surgery, especially when X-ray contrast media are used or kidney function could be under strain. This avoids the very rare risk of over-acidification of the blood. When you may take it again is told to you by the treatment team.
Bridging means that a paused blood thinner is temporarily replaced with heparin injections, in order to bridge the time without full anticoagulation when the thrombosis risk is high. Whether it is needed is decided individually by the treating practice — today it is used more selectively than in the past.
Anti-inflammatory painkillers (NSAIDs) such as Ibuprofen increase the tendency to bleed and are often paused a few days beforehand for larger procedures. Whether and for how long depends on the procedure. Raise it at the pre-op assessment, especially if you take such medicines regularly.
Yes, absolutely. Over-the-counter painkillers and herbal or high-dose preparations (e.g. St John's wort, ginkgo, fish oil) can also affect clotting and anaesthesia. On your medication list, really state everything you take regularly — nothing is too unimportant.
This is just as important as pausing and is easily forgotten. Have it put in writing when you should restart each paused medication — especially blood thinners. If unsure after discharge, ask at the practice rather than starting on your own.
Medical disclaimer: This article is for general information and does not replace medical advice. Never stop or continue medications before an operation on your own initiative — only the instruction from the pre-anaesthetic assessment is binding. With blood thinners after a stent, stopping them on your own initiative is life-threatening. Last updated: July 2026.
