How long before going under general anesthesia can you eat?

When undergoing general anesthesia for surgery or other medical procedures, patients are advised to fast (abstain from food and drink) for a period of time beforehand. This fasting helps prevent pulmonary aspiration – food or liquids from the stomach entering the lungs during anesthesia. Proper fasting helps ensure patient safety and optimal outcomes.

Guidelines for Pre-Anesthesia Fasting

Most medical experts recommend the following fasting periods before general anesthesia:

  • No solid foods for 6-8 hours prior
  • Clear liquids permitted up until 2 hours before
  • No milk or milk-containing products for 8 hours before

These guidelines can vary slightly depending on the patient, procedure, and assessing anesthesiologist. Some additional fasting recommendations include:

  • Infants can have formula up to 6 hours before anesthesia
  • No breastmilk for 4 hours prior
  • Light meal up to 6 hours before, such as toast and clear liquids
  • No gum, candy, mints in final 2 hours

Clear Liquid Diet Before Anesthesia

In the 2 hours leading up to general anesthesia, only clear fluids are permitted. These help hydrate the patient without increasing aspiration risks. Clear liquids include:

  • Water
  • Clear juice – apple, white grape, lemonade
  • Clear soda
  • Black coffee or tea (no milk/creamer)
  • Clear nutritional beverages
  • Plain gelatin
  • Popsicles without fruit or cream
  • Clear broth

Alcohol should be avoided 24 hours before anesthesia since it can interact poorly with medications given.

Purpose of Pre-Op Fasting

Pre-operative fasting is so strictly enforced because anesthesia causes several effects that increase the chances of pulmonary aspiration if stomach contents are present:

  • Relaxed esophageal sphincter allowing regurgitation
  • Reduced gastrointestinal motility
  • Unconscious airway protective reflexes

This aspiration into the airway and lungs can cause serious pneumonia, respiratory distress, lung damage, and other complications. By fasting for an appropriate time pre-surgery, patients reduce these risks.

Risks of Pre-Op Fasting

While fasting is important before anesthesia, extended periods without food or fluids can also pose health risks including:

  • Dehydration
  • Electrolyte imbalances
  • Headaches
  • Hypoglycemia
  • Anxiety
  • Dizziness
  • Fatigue

This is why clear fluids are permitted up to 2 hours pre-op – to help minimize these fasting risks. IV fluids are also started before anesthesia to help hydrate the patient.

Special Patient Populations

Certain patients may require tailored fasting recommendations from their surgeon and anesthesiologist. This includes:

  • Obese patients – prolonged fasting often recommended due to delayed gastric emptying
  • Diabetics – glucose monitoring is key during pre-op fast
  • Patients with reflux – early fasting or medication may be advised
  • Pregnant women – hydration and nutrition for mom and baby must be considered

Age-Related Fasting Guidelines

Fasting times are adjusted for pediatric and elderly patients to account for their unique needs.


  • No solid food for 6 hours before anesthesia
  • No non-clear liquids for 4-6 hours prior
  • Clear liquids permitted up to 2 hours before
  • No formula for 6 hours before
  • No breastmilk for 4 hours before

Infants Under 6 Months

  • May have formula up to 4-6 hours before anesthesia
  • No breastmilk for 3-4 hours prior
  • No solid foods for 6+ hours before

Elderly Patients

  • Conservative fasting times due to slower gastric emptying
  • Often 8+ hours fasting from solids/non-clears
  • Clear liquids may be restricted after midnight or at least 6 hours pre-op

Day Before Surgery Recommendations

Proper nutrition and hydration the day before surgery helps patients withstand the fasting period. Recommendations include:

  • Eat light, easily digestible meals
  • Avoid heavy, greasy, or fried foods
  • Do not overeat large portions
  • Stay well-hydrated by drinking fluids regularly
  • Avoid alcohol and tobacco
  • Get adequate rest

Patients may be advised to eat smaller, more frequent meals the day before their procedure while clear fluids are encouraged up until midnight.

Can You Drink Water Before Anesthesia?

Small sips of water may be allowed up to 2 hours before anesthesia, provided intake is restricted to just a few ounces. But some anesthesiologists still recommend avoiding any water within this 2 hour window if possible.

Patients scheduled early in the morning are advised to drink a few sips of water on waking up to take medications and moisten the mouth. But extensive water drinking should be avoided close to anesthesia time.

Exceptions to Fasting Guidelines

There are a few cases where fasting requirements may be adjusted on an individual basis. For example:

  • Patients on certain chronic medications may need sips of water to swallow pills up to 1 hour pre-op.
  • Those with medical conditions like adrenal insufficiency may need glucocorticoid coverage the morning of surgery, taken with sips of water.
  • Emergency surgeries often require relaxation of typical NPO guidelines.
  • Allowance of select clear liquids may occur for prolonged waiting periods before surgery.

The anesthesiologist will make final decisions about any exceptions to fasting based on the clinical scenario.

Can You Chew Gum Before Anesthesia?

Chewing gum is not permitted for at least 2 hours prior to anesthesia. While gum itself is not a concern, the chewing action stimulates digestive processes. This can increase secretions and gastrointestinal motility which airs on the side of caution, gum is restricted pre-op.

When to Start Fasting Before Surgery

Using the standard fasting guidelines, most patients should start restricting their intake at the following times:

  • No solid foods for 6-8 hours before anticipated OR time
  • No non-clear liquids for 6 hours prior
  • Clear liquids permitted until 2 hours before scheduled surgery

However, confirm specifics with your individual anesthesiologist as start times can vary.

Consequences of Not Fasting Before Anesthesia

Failing to properly fast before surgery can increase risks of pulmonary aspiration during anesthesia. Depending on severity, consequences may include:

  • Coughing, choking, shortness of breath
  • Wheezing, chest tightness
  • Cyanosis – bluish discoloration of skin
  • Tachycardia, hypoxemia
  • Bronchospasm
  • Pneumonia
  • Acute respiratory distress syndrome (ARDS)
  • Respiratory arrest

While mild aspiration may only require suctioning and increased ventilation during surgery, significant aspiration events can have life-threatening repercussions. Strict adherence to fasting guidelines is key.

Changes to Pre-Op Fasting Recommendations

Pre-procedure fasting practices have evolved over time as research has further clarified risks versus benefits. Some changes include:

  • Shift from overnight restriction of all solids and liquids to more moderate fasting times.
  • Allowance of clear fluids up to 2 hours pre-op due to hydration benefits.
  • Updated fasting guidelines for pediatrics and elderly populations.
  • Increased flexibility for medically complex patients.

While traditions of very prolonged fasts (“NPO after midnight”) were once common, current guidelines attempt to strike a balance between safety and patient comfort.

Does Anesthesia Affect Appetite After Surgery?

In the immediate post-op period, anesthesia can contribute to suppressed appetite due to its effects on the body. Mechanisms include:

  • Drug-induced nausea
  • Slowed gastrointestinal motility
  • Decreased taste and smell
  • Dry mouth, sore throat
  • Immediate post-op discomfort
  • Fatigue, drowsiness

Prolonged effects from anesthesia keeping patients from resuming normal nutrition are uncommon. But short-term appetite suppression in the early recovery phase is typical.

Resuming Eating After Anesthesia

Once awake from anesthesia, patients remain NPO until bowel function returns – passing of first flatus or stool. At that point, diet is advanced slowly with:

  • Clear liquids
  • Full liquids
  • Blanded/light solid foods
  • Regular diet as tolerated

This gradual reintroduction avoids gastrointestinal upset as the bowels continue to recover post-op. But oral intake is resumed promptly once bowel activity resumes to meet nutrition needs for healing.

Risk of Dehydration After General Anesthesia

In addition to suppressed appetite, patients also often experience:

  • Post-op nausea/vomiting
  • Diarrhea
  • Fever
  • Perspiring
  • Oozing surgical wounds

Which all contribute to dehydration risk after surgery. Dehydration signs to monitor for include:

  • Thirst
  • Dry mouth
  • Muscle cramps
  • Lightheadedness
  • Reduced urine output
  • Dark urine
  • Dry skin
  • Fatigue
  • Confusion

IV fluids and electrolyte replacement helps counteract dehydration after procedures. But encouraging early oral fluid intake is also key.

Post-Op Diet Recommendations

To help patients meet nutrition needs after anesthesia and surgery, dietary recommendations include:

  • Small, frequent portions to reduce strain on digestive system
  • High protein foods to help healing
  • Low fiber, low fat, low residue foods at first to reduce diarrhea
  • Low sugar intake if diabetes present
  • Adequate hydration with water, juices, broths
  • Balanced nutritional beverages if appetite is poor
  • Resuming normal diet as tolerated

Closely coordinating with a dietitian helps customize nutrition plans during post-op recovery.

The Bottom Line

Pre-operative fasting is crucial to minimize risks of aspiration during general anesthesia. However, extended food and fluid restriction can also negatively impact patient outcomes. Current guidelines aim for a balanced approach – fasting adequately for safety while avoiding unnecessary starvation periods.

Open communication with your anesthesia providers is key to determining appropriate fasting timeframes based on your individual health status and planned procedure.

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