Pre-operative fasting in adult patients presenting for elective surgery

Publication: 20/07/2015  
Next review: 17/02/2025  
Clinical Guideline
ID: 4272 
Approved By: Trust Clinical Guidelines Group 
Copyright© Leeds Teaching Hospitals NHS Trust 2022  


This Clinical Guideline is intended for use by healthcare professionals within Leeds unless otherwise stated.
For healthcare professionals in other trusts, please ensure that you consult relevant local and national guidance.

Guidelines for pre-operative fasting in adult patients presenting for elective surgery


The practice of pre-operative fasting aims to minimise residual gastric volume and acidity prior to surgery or other procedures. This helps reduce the incidence of aspiration pneumonitis, a potentially life-threatening condition. However, there are risks associated with excessive fasting, such as fluid shifts, electrolyte imbalance, delayed postoperative recovery and patient distress.

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Aim & Objectives

  • To provide evidence based recommendations on safe and appropriate pre-operative fasting for adult patients undergoing elective surgery.
  • These fasting guidelines apply to all adult elective patients who are diabetic, and for further management of diabetes perioperatively please follow the link here
  • In addition to guidelines on minimal fasting periods, also included are guidelines on maximum fasting periods, in an attempt to reduce prolonged fasting.
  • This document contains guidelines only, and the decision to proceed with a case rests with the individual clinicians involved in the patients' care.

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Exclusions; the guideline does NOT attempt to provide the following:

  • Fasting guidance for paediatrics
  • Fasting guidance for women in labour
  • Fasting guidance for patients having a procedure done solely under local anaesthesia infiltration

If unsure, please contact relevant department for further advice if no guidelines available on the intranet.

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Minimum Fast for Clear Fluids:

  • Patients may drink water up to 2 hours prior to the start of the list.
  • Furthermore, all patients should be encouraged to drink water up to 2 hours before surgery, unless there is a surgical contra-indication.
  • Alcohol containing drinks should not be consumed within the 24 hours prior to surgery.
  • Black tea or black coffee are acceptable alternatives to water if preferred.
  • It is safe for patients to drink carbohydrate-rich drinks in conjunction with Enhanced Recovery After Surgery (ERAS) guidelines up to 2 h before elective surgery but only drinks specifically designed for peri-operative use, for example, but not exclusively, Preload®, IMPACT®, Polycal®, Maxijul®. Omit the pre-operative high carbohydrate drink in people with insulin treated diabetes.

Minimum Fast for Solids:

  • Solids and milk-containing drinks should not be consumed within 6 hours of the beginning of the operating list.
  • Patients should eat normally on the day before surgery and avoid large or fatty meals. Fat and dietary fibre tends to remain in the stomach for longer than other foods.
  • Patients should not have their operation cancelled or delayed just because they are chewing gum, sucking a boiled sweet or smoking immediately prior to induction of anaesthesia. This is based solely on effects on gastric emptying, and nicotine intake (including smoking, nicotine gum and patches) should be discouraged before elective surgery.1 
  • Patients for a morning list should eat nothing for six hours before surgery. Realistically, most patients will not usually eat after midnight and this is a convenient cut-off point.
  • Patients for an afternoon list should have a light breakfast, for example, toast or cereal, at least 6 hours prior to the start of the list.

Prescribed Medications and Premedication:

Prescribed medications or pre-medication can be taken within the 2 hours prior to surgery with a small drink of water (<30 ml), after discussion with the relevant team.

Maximum fasting times:

All patients should be encouraged to drink clear fluids up to 2 hours prior to the start of the list (i.e. 6.00am. For morning lists and 11.00am for afternoon lists) unless this is contraindicated due to the type of surgery.

The theatre teams should endeavour to communicate a plan for the final cut-off time for water for each patient on their operating list following the team brief. If a patient has been fasted for fluids for more than three hours, ward staff should contact theatres or the anaesthetist to ask if it would be acceptable for the patient to have a drink. If not, consideration should be given to starting maintenance intravenous fluids on the ward.

Patients requiring Regional Anaesthesia only:

Fasting guidelines apply as for general anaesthesia.

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Evidence for the fasting guidelines:

The most recent evidence-based guidance on pre-operative fasting comes from the latest European Society of Anaesthesiology guidelines1, endorsed by The Association of Anaesthetists of Great Britain and Ireland.

A summary, along with rationale for the recommendations, is provided below:

  1. Adults should be allowed2 and even encouraged1, 3, 4 to drink clear fluids up to 2 hours before elective surgery.
    • Large body of evidence that this is safe1
    • Applicable to patients with obesity, gastro-oesophageal reflux disease, diabetes mellitus and pregnant women not in labour.1,4
    • Shortening fluid fast may lead to less anxiety pre-operatively with less nausea and vomiting post-operatively1,4
    • Excessively long fasting times are an inappropriate way to prepare patients for the stress response to surgery1
    • Reduces discomfort and improves wellbeing in patients.1,3
  2. Adults should be prohibited from eating solid food for 6 hours before elective surgery1, 2, 3, 4
    • No recent studies have attempted to define a minimal safe period for preoperative fasting for solid food.
    • This is common practice, although based on little evidence.
  3. Patients should not have their operation cancelled/delayed because they are chewing gum, sucking a boiled sweet or smoking immediately prior to anaesthesia.1,2,4 This is based solely on effects on gastric emptying and nicotine intake (including smoking, nicotine gum and patches) should be discouraged before elective surgery.
    • Controversial3
    • 3 semi-randomized controlled trials have shown no evidence of clinically significant complications as a result of these actions5, 6, 7.
    • Another study showed evidence of an increase in gastric volume and pH as a result of chewing gum6, 7
  4. It is safe for patients to drink carbohydrate-rich drinks 2 hours prior to anaesthesia1
    • 5 randomised controlled trials suggest that this is safe.8,9,10,11,12
    • Products specifically developed for pre-operative use i.e. not all carbohydrate drinks are necessarily safe.
    • Improved subjective well-being, reduced thirst, hunger and post-operative insulin resistance.1

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Record: 4272
Clinical condition:

Preoperative fasting guidelines in ADULT patients undergoing ELECTIVE surgery.

Target patient group: Adult patients undergoing elective surgery.
Target professional group(s): Secondary Care Doctors
Secondary Care Nurses
Adapted from:

Evidence base

  1. Smith I, Kranke P, Murat I et al. Perioperative fasting in adults and children: guidelines from the European Society of Anaesthesiology. Euro J Anaesthesiol 2011; 28(8): 556-569
  2. The Association of Anaesthetists of Great Britain and Ireland. Safety guideline: pre-operative assessment and patient preparation. AAGBI 2010; 30-31
  3. The Royal College of Nursing. Clinical practice guidelines: perioperative fasting in adults and children. RCN 2005; 26-31
  4. Smith A. Pre-operative fasting in adults: Royal College of Anaesthetists- raising the standard: a compendium of audit recipes. RCOA 2012; 80- 81
  5. Dubin SA, Jense HG, McCranie JM et al. Sugarless gum chewing before surgery does not increase gastric fluid volume or acidity. Can J Anaesth 1994; 41: 603- 606
  6. Schoenfelder RC, Ponnamma CM, Freyle D et al. Residual gastric fluid volume and chewing gum before surgery. Anesth Analg 2006; 102: 415- 417
  7. Soreide E, Hoist-Larsen H, Veel T et al. The effects of chewing gum on gastric content prior to induction of general anaesthesia. Anesth Analg 1995; 80: 985- 989
  8. Taniguchi H, Sasaki T, Fujita H et al. Preoperative fluid and electrolyte management with oral rehydration therapy. J Anesth 2009; 222-229
  9. Kaska M, Grosmanova T, Havel E et al. The impact and safety of preoperative oral or intravenous carbohydrate administration versus fasting in colorectal surgery: a randomised controlled trial. Wien Klin Wochenschr 2010; 122: 23-30
  10. Nygren J, Thorell A, Jacobsson H et al. Preoperative gastric emptying. Effects of anxiety and oral carbohydrate administration. Ann Surg 1995; 222: 728- 734
  11. Jarvela K, Maaranen P, Sisto T. Preoperative oral carbohydrate treatment before coronary artery bypass surgery. Acta Anaesthesiol Scand 2008; 52: 793- 797
  12. Breuer JP, Von Dossow V, Von Heymann C et al. Preoperative oral carbohydrate administration to ASA III-IV patients undergoing elective cardiac surgery. Anesth Analg 2006; 103: 1099- 1108

Approved By

Trust Clinical Guidelines Group

Document history

LHP version 1.0

Related information

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