Key facts
- Fasting: only required if sedation or a general anaesthetic is planned — not for procedures under local anaesthetic alone.
- GLP-1 agonists (Ozempic, Mounjaro, etc.): current guidance is to continue them, not stop them — a 24-hour clear fluid diet the day before is used instead, if sedation is planned.
- Metformin: generally continued if kidney function is normal; withheld around the procedure if kidney function is reduced, or the procedure is an arterial catheter study.
- Other diabetes medications: sulfonylureas are withheld while fasting; SGLT2 inhibitors need days-before planning for anything beyond a day-only procedure; insulin needs an individualised plan.
- Blood pressure, cholesterol and most other regular medications: generally continued as normal, including on the day of the procedure.
- When in doubt: confirm directly with our rooms — these instructions vary by procedure type and individual patient factors.
Fasting before a procedure
Whether a patient needs to fast depends entirely on whether sedation or a general anaesthetic is planned — not on the procedure itself.
In practice
Local anaesthetic only (most joint injections, many biopsies): no fasting required — patients can eat and drink normally beforehand unless told otherwise.
Sedation or general anaesthetic planned (many embolisation and ablation procedures): standard fasting applies — 6 hours for food and non-clear fluids, 2 hours for clear fluids (water, black tea or coffee), consistent with ANZCA pre-anaesthesia guidance (PG07). Always confirm the specific hospital or facility's fasting instructions, as timing can vary slightly by site.
If a patient calls reception unsure whether they need to fast, the safest response is to check what sedation, if any, is planned for their specific procedure — this isn't always obvious from the referral alone, so confirm with our rooms if uncertain.
GLP-1 receptor agonists (Ozempic, Wegovy, Mounjaro, Trulicity, and similar)
This is an area where guidance changed significantly in 2024–2025, so it's worth being explicit: current advice is to continue these medications, not stop them, before a procedure.
Why this matters
GLP-1 receptor agonists (and dual GLP-1/GIP agonists) slow gastric emptying. This has been linked to retained stomach contents and, rarely, pulmonary aspiration during sedation or general anaesthesia. The Therapeutic Goods Administration issued a Medicines Safety Update on this in 2025, and updated multi-society guidance (ANZCA, the Gastroenterological Society of Australia, the Australian Diabetes Society, and others) followed.
Earlier guidance suggested stopping GLP-1 medications for a period before a procedure. This has since been revised — it's unclear how long a medication needs to be stopped to meaningfully affect gastric emptying, and stopping it carries its own downsides for diabetes and weight management. The current approach instead manages the risk directly:
- Continue the medication as normal — do not instruct patients to stop it before their procedure
- If sedation or a general anaesthetic is planned: a 24-hour clear fluid diet is recommended, starting from waking the day before the procedure and continuing until the standard fasting period begins
- During the final 6 hours before the procedure: water is the only recommended fluid, with the patient nil by mouth for the last 2 hours — slightly more conservative than the standard fasting rule, given delayed gastric emptying can still affect fluids
- For local anaesthetic-only procedures without sedation, this extended preparation is generally not necessary — confirm with our rooms if unsure
For diabetic patients on a 24-hour clear fluid diet, particularly those on insulin, referral to their endocrinologist or diabetes team for glycaemic management advice is recommended — most carbohydrate in clear fluids is simple sugar, which can affect blood glucose control differently to a normal diet.
Other diabetes medications
Metformin and GLP-1 agonists get asked about most often, but patients are frequently on a combination of diabetes medications. This is one of the most common questions reception fields, so it's worth having a clear reference rather than guessing per class:
| Medication class | Examples | Guidance |
|---|---|---|
| Sulfonylureas | Gliclazide, glimepiride | Withhold the dose due while fasting (hypoglycaemia risk with no food intake); resume with the next meal |
| DPP-4 inhibitors | Sitagliptin, linagliptin, saxagliptin | Continue as normal — low hypoglycaemia risk on their own |
| Thiazolidinediones | Pioglitazone | Continue as normal |
| SGLT2 inhibitors | Dapagliflozin (Forxiga), empagliflozin (Jardiance) | Day-only procedure: withhold on the day of the procedure only. Procedure involving an overnight stay or a bowel-preparation-type fast: withhold 2–3 days beforehand and on the day. Risk is euglycaemic diabetic ketoacidosis — can occur with a normal blood glucose reading, so it isn't picked up by glucose monitoring alone |
| GLP-1 receptor agonists | Semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro), dulaglutide (Trulicity) | Continue — see the dedicated section above |
| Insulin | Basal, mealtime, or pre-mixed | Individualised — generally basal/long-acting insulin is continued, sometimes at a reduced dose; mealtime insulin is withheld while fasting; pre-mixed insulin often needs a reduced morning dose. This should be planned with the patient's usual prescriber or diabetes team, not decided at reception |
In practice
For day-only procedures under local anaesthetic, most diabetes medications don't need any adjustment at all, since the patient isn't fasting. Medication adjustments become relevant specifically when a procedure involves fasting for sedation or a general anaesthetic — if in doubt, ask what's planned for the specific procedure before giving instructions.
Metformin and contrast
Metformin guidance is tied to kidney function and the type of procedure, not a blanket rule. Current guidance (ACR Manual on Contrast Media) categorises patients as follows:
| Patient category | Metformin instruction |
|---|---|
| eGFR ≥ 30 mL/min/1.73m², no acute kidney injury | Continue as normal — no need to stop before or after the procedure, and no routine need to recheck kidney function afterward |
| eGFR < 30 mL/min/1.73m², or known acute kidney injury | Withhold at the time of the procedure; hold for 48 hours afterward; restart only once kidney function is confirmed stable |
| Any arterial catheter procedure with a risk of embolisation to the kidneys | Withhold at the time of the procedure; hold for 48 hours afterward; restart only once kidney function is confirmed stable — regardless of baseline eGFR |
Why the third category matters here
Many interventional radiology procedures are arterial catheter studies — this includes embolisation procedures such as GAE, UFE, and PAE. These carry a small risk of affecting the renal arteries regardless of how well the kidneys were functioning beforehand, which is why metformin is generally withheld around these specific procedures even in patients with normal kidney function. This is more conservative than the rule for a routine contrast CT scan.
Fasting is not required purely because contrast will be given — the ACR is explicit that fasting before intravascular contrast administration is not supported by evidence and can cause unnecessary harm, including hypoglycaemia in diabetic patients. Any fasting instruction relates to sedation, not the contrast itself.
Other regular medications — blood pressure, cholesterol, and more
Reception staff are often asked whether a patient should take their usual tablets on the morning of a procedure. As a general principle: most regular medications should be taken as normal, including on the day of the procedure — with a small sip of water even during a fasting period. A small number of specific classes are the exceptions:
| Medication | Guidance |
|---|---|
| Statins (cholesterol) | Continue as normal |
| Beta-blockers, calcium channel blockers | Continue as normal — stopping a beta-blocker abruptly can cause rebound hypertension or a fast heart rate |
| ACE inhibitors / ARBs | Continue for local anaesthetic or sedation-only procedures. For a procedure involving a general anaesthetic, these are often omitted on the morning of the procedure due to a risk of low blood pressure under anaesthesia — confirm with the treating anaesthetist |
| Diuretics ("water tablets") | Sometimes withheld on the morning of a procedure requiring fasting or sedation, mainly for practical reasons (needing the bathroom during a fasting or immobile period) rather than a specific safety concern — confirm locally |
| Thyroid hormone (e.g. levothyroxine) | Continue as normal |
| Long-term corticosteroids (e.g. prednisone for an unrelated condition) | Continue — do not stop abruptly, given the risk of adrenal insufficiency. Larger procedures may need a temporary dose adjustment; this should be planned with the prescribing doctor in advance |
| Anticoagulants and antiplatelet medications | See our separate periprocedural anticoagulation & antiplatelet guide — these follow a different framework based on bleeding risk, not fasting |
Common questions
Do all patients need to fast before an interventional radiology procedure?
No. Fasting is generally only required if sedation or general anaesthesia is planned. Procedures performed under local anaesthetic alone typically do not require fasting, unless specifically instructed otherwise.
How long should a patient fast before sedation or a general anaesthetic?
The standard fasting period is 6 hours for food and non-clear fluids, and 2 hours for clear fluids (water, black tea or coffee), consistent with ANZCA guidance. Local hospital or facility policy should always be confirmed.
Should patients stop taking Ozempic, Mounjaro or other GLP-1 medications before a procedure?
Current ANZCA guidance (updated 2025) recommends continuing GLP-1 receptor agonists and not ceasing them before a procedure. Instead, risk is managed through a 24-hour clear fluid diet the day before, for patients having sedation or a general anaesthetic.
Why is there special guidance for GLP-1 medications like Ozempic?
GLP-1 receptor agonists delay gastric emptying, which has been linked to a small but serious risk of retained stomach contents and pulmonary aspiration during sedation or general anaesthesia. The TGA issued a safety update on this in 2025.
Does metformin need to be stopped before a contrast scan or procedure?
For patients with an eGFR of 30 mL/min/1.73m² or above and no acute kidney injury, metformin does not need to be stopped. For patients with reduced kidney function, acute kidney injury, or an arterial catheter procedure with a risk of embolisation to the kidneys, metformin should be withheld at the time of the procedure and for 48 hours afterward.
Why do arterial procedures have stricter metformin guidance than a CT scan?
Arterial catheter procedures carry a small risk of embolisation to the renal arteries, which can affect kidney function independently of eGFR. Because of this added risk, current guidance recommends withholding metformin around these procedures regardless of baseline kidney function.
What about other diabetes medications besides metformin — sulfonylureas, SGLT2 inhibitors, insulin?
Sulfonylureas are generally withheld while fasting due to hypoglycaemia risk. SGLT2 inhibitors (e.g. dapagliflozin, empagliflozin) are withheld on the day of a day-only procedure, or for 2–3 days beforehand if the procedure involves an overnight stay or bowel preparation, due to a risk of euglycaemic diabetic ketoacidosis. Insulin requires an individualised plan, usually made with the patient's diabetes team. DPP-4 inhibitors and thiazolidinediones are generally continued as normal.
Should patients stop their blood pressure or cholesterol medication before a procedure?
Generally no. Statins, beta-blockers, calcium channel blockers, and thyroid medication are continued as normal. ACE inhibitors and ARBs are usually continued for local anaesthetic or sedation-only procedures, but are sometimes omitted on the morning of a procedure involving a general anaesthetic due to a risk of low blood pressure — this should be confirmed with the treating anaesthetist.
This page provides general, guideline-informed information for reception staff, referrers and patients, and does not replace individualised clinical advice or current local hospital policy. Clinical judgement should always be used — please confirm specific instructions with our rooms for any patient whose situation is complex, or where guidance may have been updated since this page was last reviewed.
This page does not cover every medication relevant to periprocedural preparation. For anticoagulant and antiplatelet medications specifically, see our separate periprocedural anticoagulation & antiplatelet guide. For an interactive, case-by-case version of the guidance on this page, see our interactive diabetes & regular medications guide.
Not sure about a specific patient?
Get in touch before the appointment
If a patient's situation doesn't clearly fit the guidance above — multiple relevant medications, reduced kidney function, or an unusual procedure combination — contact our rooms ahead of the booking rather than guessing.
Contact our rooms- Australian and New Zealand College of Anaesthetists (ANZCA), Gastroenterological Society of Australia, Australian Diabetes Society, National Association of Clinical Obesity Services, and Australian and New Zealand Metabolic and Obesity Surgery Society. Clinical Practice Recommendations: Periprocedural GLP-1RA Use. April 2025 (updated). anzca.edu.au
- Therapeutic Goods Administration (TGA). Medicines Safety Update: GLP-1 and dual GIP/GLP-1 receptor agonists. 2025.
- El-Boghdadly K, Dhesi J, Fabb P, et al. Elective peri-operative management of adults taking glucagon-like peptide-1 receptor agonists, glucose-dependent insulinotropic peptide agonists and sodium-glucose cotransporter-2 inhibitors: a multidisciplinary consensus statement. Anaesthesia. 2025;80(4):412-424.
- ANZCA PG07: Guideline on pre-anaesthesia consultation, Appendix 1 (fasting). 2024.
- American College of Radiology (ACR). ACR Manual on Contrast Media — Metformin chapter and Fasting Prior to Intravascular Contrast Media Administration chapter. 2024–2025 editions.
- Australian Diabetes Society (ADS) and ANZCA. ADS-ANZCA Perioperative Diabetes and Hyperglycaemia Guidelines (Adults). 2022.