The preoperative workup for a breast augmentation: tests, medication and habits that need adjusting

The preoperative workup is not an administrative formality: it is where the things that can complicate an otherwise very safe operation are picked up.

This page explains what is reviewed and why, and sets out in detail one point that has changed in recent years and that almost no website has taken on board yet: weight-loss drugs and their effect on anaesthesia.

The tests

The aim is twofold: to confirm that you can safely undergo a general anaesthetic and to have an image of your breast before the surgery.

What a preoperative assessment of this kind usually includes:

• Blood tests, with a full blood count and clotting studies.
• An electrocardiogram and, depending on age and history, other cardiorespiratory tests.
• Breast imaging —ultrasound or mammogram— according to age and to personal and family history.
• Assessment by the anaesthetist, who is the person who gives the final go-ahead and sets the definitive instructions. 🔑 And they are also the person who, once in theatre and before starting, places a block of the intercostal nerves with ropivacaine to improve the pain of the first few hours: it is explained in the page on anaesthesia.

🔑 The prior breast imaging deserves a note. It serves two purposes: to rule out findings that would change the indication, and to put on record what your breast was like beforehand, which is a useful reference for every later check-up.

🔑 The clinic’s rule: here breast imaging is ALWAYS requested. Ultrasound and/or mammogram, whichever applies to your case — it is not tied to a minimum age. And with it, always preoperative blood tests and an electrocardiogram and a pre-anaesthetic assessment.

It is our own criterion, and it answers to the two reasons in the previous paragraph: to rule out findings that would change the indication, and to put on record what your breast was like before surgery.

⚠️ What does depend on your age and your history are the tests added to those —other cardiorespiratory investigations, for example— and how far in advance they are requested. That is set by the team with your history in front of them.

The medication

It is the part that produces the most surprises, because many people do not think of a good deal of what they take as “medication”.

What has to be declared without exception:

• Anticoagulants and antiplatelet drugs.
• Anti-inflammatories, including aspirin and the ones taken occasionally.
• Hormonal contraceptives and hormone therapy.
• Antidepressants, anxiolytics and any psychiatric treatment.
• Treatments for diabetes or for weight loss, with the detail of the next section.
• ⚠️ Supplements, vitamins and herbal products. Several affect clotting and appear on no prescription.

The practical rule is simple: take the complete list of everything you take, with name and dose, and let the team decide what is stopped and when. Stopping a long-term treatment on your own initiative can be worse than keeping it.

Who decides the intervals here: the anaesthetist. And that is also why this page does not publish any figure in days.

The intervals for an anticoagulant or an antiplatelet drug depend on the particular drug, on what you take it for —preventing is not the same as treating— and on your own risk of thrombosis against your risk of bleeding. It is an individual medical decision, not a figure that can be given in writing to everybody at once. Publishing a number here would be false precision.

🔑 Weight-loss drugs and anaesthesia

This is the point that has changed and the one that justifies this page.

What they are. GLP-1 receptor agonists are drugs used for type 2 diabetes and, in recent years, for weight control. Part of their mechanism consists of slowing the emptying of the stomach, which is what reduces appetite.

Why it matters in theatre. Preoperative fasting exists so that the stomach is empty at the moment of the anaesthetic and there is no risk of its contents passing into the airway. If emptying is slowed, observing the fast may not be enough.

What was measured. A study published in 2024 in JAMA Surgery examined with gastric ultrasound 124 people who were about to undergo an elective procedure under anaesthesia and had observed the fasting guidelines:

	Increased residual gastric content
Taking a weekly GLP-1	56% (35 of 62)
Not taking one	19% (12 of 62)

After adjusting for confounders, taking the drug was associated with a prevalence 30.5 points higher (95% CI: 9.9-51.2), with an adjusted prevalence ratio of 2.48.

⚠️ And here is the figure that changes what has to be done:

There was no association between how long the drug had been stopped and the prevalence of increased gastric content (adjusted odds ratio 0.86; 95% CI: 0.65-1.14).

The authors conclude that the fasting duration suggested by current guidelines may be inadequate in this group of patients, who have an increased risk of aspiration under anaesthesia.

🔑 That result is the one that has changed everybody’s practice, and it is worth understanding before going on: if how long you have gone without taking it does not predict what is in your stomach, stopping it is not the safety measure it appeared to be. What does work is the anaesthetic team knowing about it and adapting the preparation — a different fast, a liquid diet beforehand, a gastric ultrasound before putting you to sleep or specific precautions at induction.

⚠️ And the recommendations have changed in recent years and are still evolving. This is what is done today:

The clinic’s approach to a GLP-1: shared decision-making, not automatic discontinuation

Here you are not asked to stop it as a rule. The approach is the one recommended by the scientific societies that have reached agreement on this, and they are worth naming because that is what gives the answer its weight: the 2024 multisociety guidance, approved by the American Gastroenterological Association, the American Society for Metabolic and Bariatric Surgery, the American Society of Anesthesiologists, the International Society of Perioperative Care of Patients with Obesity and the Society of American Gastrointestinal and Endoscopic Surgeons.

And what that guidance says is this:

• 🔑 The decision is a shared one between the patient, the surgical team, the anaesthetic team and whoever prescribes the drug. There is no rule that works for everybody, because two things have to be weighed at once: the metabolic need for the treatment and the individual risk.
• It is not stopped across the board. What is done is to reduce the risk of aspiration by other routes: modifying the preoperative diet —clear liquids for the 24 hours beforehand— and/or adjusting the anaesthetic plan, with a rapid sequence induction if appropriate.
• ⚠️ The guidance itself is presented as guidance and not as an evidence-based guideline. That is honest of them and worth repeating: this is ground that is still moving.

“I was told to stop it a week beforehand”

That is quite possible, and it was not a mistake: it is what the previous guidance recommended. In 2023 the American Society of Anesthesiologists published consensus-based guidance saying to stop the weekly ones a week beforehand and the daily ones on the day of the procedure, for everybody and for any operation.

⚠️ The 2024 guidance replaced that approach —one interval for everyone— with shared decision-making. If you have been given the week-beforehand instruction, do not ignore it because you have read this page: raise it at the pre-anaesthetic assessment, which is where your case is decided.

Why it has moved this way. Because a fixed interval would give false reassurance: stopping the drug does not guarantee that the stomach is empty. It is exactly what the study above measured —how long it had been stopped was not associated with less gastric content— and it is the reason the useful course of action is to give notice, not to stop taking it on your own initiative.

🚨 So what you have to do is still one single thing: say so. With name and dose, at the pre-anaesthetic assessment. From there the anaesthetist decides what preparation to ask for in your case.

The other half, which almost nobody mentions: nutritional status

There is a second reason to discuss these drugs at the preoperative stage, and it has nothing to do with the stomach: part of the weight lost with them is lean mass. In the published trials that proportion varies a great deal —between around 15% and 60% of the weight lost, depending on the study— and arriving in theatre with an impoverished nutritional status means arriving in worse condition to heal.

🔑 And this is not a hunch: in breast surgery it has been measured, and the factor that counted was not the weight lost but a low albumin. It is set out in full in the page on the breast after weight loss, with the figures.

The important thing is that it is correctable, and without stopping the treatment: by pushing a high-protein diet in the days before and after surgery. In active weight loss with these drugs, between 1.2 and 1.6 g of protein per kilo of body weight per day is proposed, precisely in order to preserve lean mass. It is something agreed in consultation, and it is more useful than stopping: stopping does not feed you.

The habits

Smoking

It is the modifiable factor that weighs most. The FDA names it expressly among the causes of necrosis of breast tissue, alongside infection and other factors.

🔑 The clinic’s interval: a month before surgery and a month after. With no exceptions by procedure — it is the same for all the surgery done here.

⚠️ And vaping counts. What is asked for is stopping the nicotine, not changing its format.

Weight

Stable before surgery. The breast is in good part fatty tissue: if your weight is going to change significantly, the result will change with it, and a large loss can also add laxity that changes the indication.

If you are in the middle of losing weight, the sensible course is to finish and stabilise before scheduling surgery. It is set out in full in the page on who is a candidate.

Alcohol and rest

Both affect clotting and recovery. There is no magic figure; but it is worth arriving in the best possible condition for elective surgery that you choose and schedule.

The fast and the last few hours

Preoperative fasting is a safety instruction, not a formality, and it is exactly where everything above comes into play.

The fast asked for here is 8 hours. It is the reference around which your arrival time is organised, and that is why first-thing operations are appreciated: the fast falls almost entirely at night.

⚠️ Two things can change it, and that is why what the anaesthetist tells you always rules. The first, GLP-1 drugs: if the emptying of the stomach is slowed, observing the fast may not be enough —which is what the study above measures— and the preparation is adjusted. The second, your own medication: there are tablets that are taken that morning anyway with a sip of water, and that too is for them to say.

🔑 And one clarification that avoids the commonest mistake: fasting is not “nothing to drink since yesterday”. Holding out for more hours than necessary adds no safety and does leave you in worse shape for surgery. Follow the time you are given, not the one that seems more prudent to you.

What is worth having sorted the day before:

• The shower with whichever soap you are told to use, if one has been prescribed.
• No jewellery, nail varnish, make-up or contact lenses.
• Comfortable clothes that fasten at the front, because afterwards you will not be able to raise your arms properly.
• Someone to come with you and take you home. You will not be able to drive.
• The house made ready: whatever you need, at waist or chest height, not on high shelves.

What is decided beforehand and not in theatre

It is worth saying because it is reassuring: the volume, the type of implant, the plane and the approach are decided in consultation, not as you go along. What can be adjusted during surgery are fine details, within what was planned and consented to.

How those decisions are reached is in the page on the first consultation and in the guide to choosing the size.

And what you sign and what must be given to you, in the page on consent and documentation.

Frequently asked questions

What tests will I be asked for before surgery?

Here, always: blood tests with clotting studies, an electrocardiogram, breast imaging —ultrasound and/or mammogram— without tying it to a minimum age and a pre-anaesthetic assessment. The person who gives the final go-ahead and the definitive instructions is the anaesthetist, and they may add other tests according to your age and your history.

I am taking a GLP-1 weight-loss drug. Do I stop it?

Not on your own initiative, and here you are not asked to stop it as a rule. The approach followed is that of the 2024 multisociety guidance —signed by anaesthetists, gastroenterologists and metabolic surgeons—: shared decision-making, without blanket discontinuation, reducing the risk with a clear liquid diet for the 24 hours beforehand and/or adjusting the anaesthetic plan.

⚠️ What is compulsory is saying so. In a 2024 study using gastric ultrasound, 56% of those taking it had increased residual gastric content despite having observed the fast, against 19% of those who did not — and, crucially, stopping the drug was not associated with a lower prevalence. That is why stopping it gives no safety and giving notice does: it makes it possible to adapt the preparation.

And what about lean mass? Wouldn’t it be better to stop it so as to heal better?

It is a reasonable worry, because part of the weight lost with these drugs is lean mass. But the answer is not to stop: it is to eat better. A high-protein diet is agreed for the days before and after —of the order of 1.2 to 1.6 g of protein per kilo per day—, which is what preserves lean mass. In breast surgery, the risk factor that has been identified is a low albumin, not the weight lost, and albumin is corrected before surgery.

Do I have to stop smoking?

Yes, and here with a specific interval: a month before and a month after. The FDA names smoking among the causes of necrosis of breast tissue. Vaping counts just the same.

How many hours of fasting are needed?

Eight. It is the clinic’s rule and the reference from which you will be given your arrival time. ⚠️ It can change if you take a GLP-1 drug or any medication that has to be kept up that morning, so the instruction that rules is the anaesthetist’s. And do not lengthen the fast on your own initiative: more hours do not give more safety.

Can I carry on with my contraceptives?

It is one of the things reviewed at the preoperative assessment, along with the rest of your medication. It is not a decision to be taken by reading: the intervals for stopping any drug are set by the anaesthetist, with your history in front of them.

Will I be given anything for the pain during surgery?

Yes. Our anaesthetists always place, before the operation starts, a block of the intercostal nerves with ropivacaine, a local anaesthetic that helps control the pain of the first 12 hours. It is explained on the page about anaesthesia.

Do herbal supplements count?

Yes, and they are the thing most often forgotten. Several affect clotting. Take the complete list of everything you take, with name and dose.

And if I am losing weight?

The sensible course is to stabilise first. The breast is in good part fatty tissue and the result moves with your weight; on top of that, a large loss can change the indication.

Is anything decided in theatre?

The volume, the implant, the plane and the approach are decided in consultation. During surgery fine details are adjusted within what was planned and consented to.

Sources

• Sen S, et al. Glucagon-Like Peptide-1 Receptor Agonist Use and Residual Gastric Content Before Anesthesia. JAMA Surgery, 2024. PMID 38446466. — Prospective cross-sectional study at a tertiary university hospital with 124 participants who had followed the pre-procedure fasting guidelines: prevalence of increased residual gastric content of 56% (35 of 62) in users of a weekly GLP-1 agonist against 19% (12 of 62) in non-users; after adjustment for confounders, an association with a prevalence 30.5 points higher (95% CI: 9.9-51.2) and an adjusted prevalence ratio of 2.48 (1.23-4.97); no association between how long the drug had been stopped and the prevalence of increased gastric content (adjusted odds ratio 0.86; 95% CI: 0.65-1.14); the authors conclude that the fasting duration suggested by current guidelines may be inadequate in this group.
• Risks and Complications of Breast Implants. U.S. Food and Drug Administration, updated 14 December 2023. fda.gov. — Smoking among the causes of necrosis of breast tissue, alongside infection, the use of steroids in the surgical pocket and chemotherapy or radiotherapy.
• American Society of Anesthesiologists Consensus-Based Guidance on Preoperative Management of Patients on Glucagon-Like Peptide-1 (GLP-1) Receptor Agonists. ASA, 29 June 2023. asahq.org. — It recommends stopping GLP-1 agonists given weekly a week before the procedure and those given daily on the day of the procedure, regardless of the indication, the dose and the type of surgery; stated reason: delayed gastric emptying and the risk of regurgitation and aspiration. ⚠️ This is the PREVIOUS position, and it is cited here for that reason: the 2024 multisociety guidance replaced the uniform interval with shared decision-making. It is kept on the page because many patients arrive having been given this instruction.
• Kindel TL, et al. Multisociety Clinical Practice Guidance for the Safe Use of Glucagon-like Peptide-1 Receptor Agonists in the Perioperative Period. Approved by the American Gastroenterological Association, the American Society for Metabolic and Bariatric Surgery, the American Society of Anesthesiologists, the International Society of Perioperative Care of Patients with Obesity and the Society of American Gastrointestinal and Endoscopic Surgeons, 2024. PMID 39480373. — It replaces blanket discontinuation with shared decision-making between patient and teams, with modification of the preoperative diet —liquids for the 24 h beforehand— and/or adjustment of the anaesthetic plan. The document expressly presents itself as guidance and not as an evidence-based guideline.
• Neeland IJ, Linge J, Birkenfeld AL. Changes in lean body mass with glucagon-like peptide-1-based therapies and mitigation strategies. Diabetes, Obesity and Metabolism, 2024. PMID 38937282. — Weight loss induced by GLP-1 agonists and by dual GLP-1/GIP agonists is accompanied by a loss of lean mass, with heterogeneous results between trials: reductions of between 40% and 60% of the total weight lost in some studies and of around 15% or less in others. The basis of the nutritional part of the clinic’s criterion.

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The most useful list you can prepare for your preoperative consultation is the one of everything you take: medication, contraceptives, supplements and herbal products, with name and dose. At our practice in Valencia that review is part of the preoperative workup, and it is where most of the things worth adjusting beforehand are picked up.

Clinical confirmation by the surgeon