What Does NBM Mean? Understanding Nil by Mouth in Pharmacology

October 5, 2025 •

5 min read

According to a 2024 survey of intensive care professionals, 97% reported witnessing patient discomfort or distress when NBM. When healthcare professionals use the abbreviation NBM, they are referring to "nil by mouth," a critical patient care and pharmacology instruction. This directive prohibits any oral intake—including food, fluids, and medications—and is essential for patient safety during a variety of medical procedures.

Quick Summary

The abbreviation NBM signifies a medical order restricting oral intake, crucial for preventing life-threatening aspiration during procedures or in specific medical conditions. Its use has significant pharmacological implications for medication administration and requires a multidisciplinary approach to patient care.

Key Points

Nil by mouth: NBM means no food, drink, or medication can be consumed orally.
Aspiration Prevention: The primary purpose of an NBM order is to prevent life-threatening aspiration, especially during general anesthesia.
Medication Management: NBM necessitates a review of all medications, with critical ones potentially requiring alternative administration routes, such as intravenous (IV) or rectal.
Patient Safety: Failure to observe NBM can lead to severe complications like aspiration pneumonia, dehydration, and malnutrition.
Clear Communication: Proper documentation, clear signage, and effective communication among the multidisciplinary team are vital to prevent errors.
Oral Hygiene: Regular mouth care is a standard part of managing NBM patients to maintain comfort and prevent infections.

What is NBM and Its Purpose?

NBM is a direct abbreviation for "nil by mouth". It is a medical instruction given to a patient to abstain from consuming anything orally, including food, drinks, and medications. The primary and most critical reason for an NBM order is to prevent pulmonary aspiration, a potentially life-threatening complication where stomach contents are inhaled into the lungs.

When a patient is under general anesthesia, the protective airway reflexes are diminished. If the stomach is not empty, there is a significant risk that its contents could be regurgitated and aspirated into the lungs. This can cause severe complications, such as aspiration pneumonitis, which has a very high mortality rate. By ensuring the patient's stomach is empty, the medical team dramatically reduces this risk.

Medical Situations Requiring an NBM Order

While most commonly associated with surgical procedures, NBM orders are implemented for a wide range of clinical scenarios to ensure patient safety.

Common indications for an NBM order include:

Pre-operative fasting: Fasting times vary depending on the procedure and type of intake. Clear fluids might be restricted for a couple of hours, while solid food requires a longer fasting period, often 6 to 8 hours. Specific guidelines exist for different populations, such as adults, children, and pregnant individuals.
Dysphagia: Patients with swallowing difficulties, often due to a stroke or other neurological conditions, are at high risk of aspiration. An NBM order protects them while a Speech and Language Therapist (SLT) assesses their swallowing ability.
Gastrointestinal (GI) rest: In certain conditions, such as gastrointestinal bleeding or pancreatitis, the digestive system needs to rest to facilitate healing. NBM orders are crucial in these cases to prevent exacerbating the condition.
Emergency procedures: In emergency situations, such as trauma, a patient's stomach is considered full, and an anesthesiologist will take special precautions to prevent aspiration during rapid sequence induction.
Reduced consciousness: Unconscious or drowsy patients may lose their protective airway reflexes and are at high risk of aspirating any food or liquid given orally.

Pharmacological Implications and Medication Management

An NBM order directly impacts a patient's medication regimen. It's a misconception that all medications should simply be withheld. Instead, a careful review by a multidisciplinary team (including doctors, pharmacists, and nurses) is essential to determine the best course of action.

Key pharmacological considerations for NBM patients:

Assessment of critical medications: Life-sustaining medications, such as those for diabetes, heart conditions, or epilepsy, cannot be omitted without careful consideration. The decision to withhold, adjust, or find an alternative route for a medication must be made by the medical team.
Alternative routes of administration: If oral medications are restricted, alternative routes must be explored to ensure the patient receives necessary treatment. This might include intravenous (IV), intramuscular (IM), rectal, or other non-oral methods.
Insulin and diabetic care: Diabetic patients require particularly careful management when NBM to avoid hypoglycemia. Blood glucose levels must be monitored closely, and insulin or oral antidiabetic medications may be adjusted or temporarily discontinued.
Anticoagulants: Anti-platelet and anticoagulant medications often need to be held before surgery to reduce the risk of excessive bleeding.

Alternative Administration Routes for NBM Patients

When an oral route is not an option, healthcare providers can utilize several alternatives for medication delivery. This list provides examples of common alternative routes and considerations:

Intravenous (IV): Medications are injected directly into a vein, providing rapid and reliable delivery. Often used for fluids, antibiotics, and critical medications.
Intramuscular (IM): Injections into a muscle, often for vaccines or medications that need slower absorption than IV.
Subcutaneous (SC): Injections into the fatty tissue just under the skin, commonly used for insulin.
Rectal: Medications can be delivered as suppositories, useful for patients who are vomiting or unable to swallow.
Transdermal: Patches or creams applied to the skin can deliver medication systemically over time, bypassing the GI tract completely.
Buccal/Sublingual: Medications placed between the cheek and gum (buccal) or under the tongue (sublingual) for rapid absorption, avoiding the first-pass metabolism in the liver.

NBM vs. NPO: A Quick Comparison

While the terms are often used interchangeably in healthcare, there is a subtle difference in origin and regional preference.


Feature	NBM (Nil By Mouth)	NPO (Nil Per Os)
Origin	English phrase meaning "nothing by mouth".	Latin phrase meaning "nothing through the mouth".
Common Use	More commonly used in the United Kingdom and some other Commonwealth countries.	More widely used in the United States and other regions.
Practical Meaning	No oral intake of food, drink, or medications.	Same as NBM: no oral intake of food, drink, or medications.
Medication Handling	Oral medications withheld, with alternatives considered by the care team.	Identical: oral medications withheld, requiring a review for alternative administration.
Primary Goal	To prevent pulmonary aspiration during procedures or manage specific clinical conditions.	Same as NBM: to prevent pulmonary aspiration.

Best Practices for Patient Care and Communication

Effective management of NBM patients goes beyond simply writing the order. Poorly supervised NBM orders and communication breakdowns can lead to significant patient harm, including dehydration, malnutrition, and incorrect medication management.

Best practices include:

Clear documentation: All NBM orders must be documented clearly in the patient's record, including the reason for the order, start time, and review time.
Patient and family communication: Patients and their families should be informed about the NBM status and the reasons for it. This helps ensure compliance and provides reassurance.
Multidisciplinary communication: All members of the care team, from nurses and doctors to pharmacists and catering staff, must be aware of the patient's NBM status. This is crucial during handovers and shift changes.
Regular review: An NBM order should be reviewed daily to assess if it is still necessary. Prolonged periods of NBM increase risks of dehydration and malnutrition.
Oral hygiene: Keeping the mouth clean and moist is essential for patient comfort, especially during prolonged NBM. Nurses can provide mouth care using moistened swabs or gels.

Conclusion

NBM, or "nil by mouth," is a fundamental safety instruction in pharmacology and patient care, particularly relevant for surgery and managing compromised swallowing. Understanding what NBM means and its implications for medication is crucial for all healthcare professionals. By adhering to proper protocols, clearly communicating with patients and colleagues, and proactively managing medication regimens, healthcare teams can mitigate the significant risks associated with restricted oral intake. Ensuring proper alternatives are in place for critical medications and regularly reviewing the need for the NBM order are paramount to providing safe, high-quality patient care.

For more detailed clinical guidelines on managing patients who are nil by mouth, resources from organizations like the Royal College of Physicians of Edinburgh can be invaluable.

Frequently Asked Questions

The primary risk is pulmonary aspiration, where food or liquid enters the lungs. This can cause a severe and potentially fatal lung infection called aspiration pneumonia, especially if the patient is sedated or has a compromised swallowing reflex.

Yes, an NBM order strictly prohibits the oral intake of all substances, including medications. The healthcare team must evaluate critical medications and arrange for alternative delivery methods or temporary adjustments.

NBM stands for "nil by mouth" (English), and NPO stands for "nil per os" (Latin), but they mean the same thing: nothing by mouth. NBM is more commonly used in the UK, while NPO is prevalent in the US.

If a medication is critical, the healthcare team will administer it via an alternative route. This could be intravenously (IV), rectally, intramuscularly (IM), or through a skin patch, depending on the medication.

Besides surgery, NBM is ordered for patients with swallowing difficulties (dysphagia), certain gastrointestinal conditions requiring "gut rest," or when a patient's consciousness is impaired.

Patients on prolonged NBM orders are at risk of dehydration, malnutrition, and electrolyte imbalances. The medical team will typically use intravenous fluids and potentially other feeding methods, like a nasogastric tube or parenteral nutrition, to provide necessary nutrients and hydration.

For patients who are NBM, regular oral hygiene is essential to prevent discomfort and reduce the risk of mouth or chest infections. This typically involves using moistened swabs or a small toothbrush with toothpaste, ensuring the patient does not swallow any fluid.