What are the SAM criteria for malnutrition?

January 13, 2026 •

2 min read

Severe acute malnutrition (SAM) affects millions of children under 5 globally, contributing significantly to child mortality. Understanding what are the SAM criteria for malnutrition is crucial for identification and treatment.

Quick Summary

This guide outlines the World Health Organization's criteria for diagnosing severe acute malnutrition (SAM) in children 6-59 months, including weight-for-height z-score, MUAC, and bilateral pitting oedema.

Key Points

SAM is defined by WHO: The World Health Organization defines severe acute malnutrition based on three primary criteria for children aged 6 to 59 months.
Low Mid-Upper Arm Circumference (MUAC): A MUAC measurement of less than 115mm is a diagnostic criterion, used for screening.
Low Weight-for-Height Z-score (WHZ): A WHZ below -3 standard deviations (SD) is an indicator of severe wasting, typically measured in clinical environments.
Bilateral Pitting Oedema: The presence of this clinical sign, on its own, confirms a diagnosis of SAM.
Combined Assessment is Best: Health organizations recommend using all three criteria to improve detection and treatment coverage.
Diagnostic Methods Vary: MUAC and oedema checks are simple for community use, while WHZ requires specialized equipment.
Early Detection is Crucial: Prompt identification of SAM using these criteria is essential for reducing the risk of complications and death in vulnerable children.
Diagnostic Tool Comparison: While MUAC is quicker, WHZ is more specific for certain types of severe wasting. Bilateral oedema is a critical, visually identifiable sign.

Understanding Severe Acute Malnutrition (SAM)

Severe Acute Malnutrition (SAM) is a life-threatening condition requiring prompt recognition and treatment. Organizations like the World Health Organization (WHO) provide criteria to standardize SAM diagnosis, especially in children aged 6–59 months. Consistent identification is key. The official SAM criteria are based on three indicators:

The Three Official SAM Criteria

For children aged 6–59 months, SAM is diagnosed if any of these conditions are met:

Mid-Upper Arm Circumference (MUAC) <115 mm: MUAC is a screening tool. A measurement below 115mm indicates severe wasting.
Weight-for-Height/Length Z-score (WHZ) < -3 Standard Deviations: Used clinically, WHZ compares a child's weight to a reference population. A score below -3 SD indicates severe wasting.
Presence of Bilateral Pitting Oedema: This clinical sign alone is sufficient for a SAM diagnosis. It is detected by pressing a thumb on both feet; if a pit remains, oedema is present.

Practical Application and Assessment

Diagnosing SAM uses these criteria and clinical examination. MUAC and oedema checks are common for community screening; WHZ is more clinical. A full assessment includes checking for complications and performing an appetite test.

Comparison of Diagnostic Criteria


Feature	Weight-for-Height Z-score (WHZ)	Mid-Upper Arm Circumference (MUAC)	Bilateral Pitting Oedema
Application	Primary tool in clinical settings.	Screening tool for community settings.	Primary clinical sign.
Measurement	Compares weight to a reference population of same height and gender.	Measures upper arm circumference.	Thumb pressure on feet checks for indentation.
Cut-off	Less than -3 standard deviations (SD).	Less than 115 millimetres (6-59 months).	Presence of swelling that 'pits' after pressure.
Advantages	Highly specific and reliable.	Easy, quick, requires minimal training.	Clear, definitive clinical sign.
Limitations	Requires accurate equipment; complex.	Can identify a different subset of children than WHZ.	May require confirmation.

The Importance of a Unified Approach

Using all three SAM criteria is recommended for a comprehensive approach to improve outcomes. This helps identify high-risk individuals. Research continues to refine protocols.

Conclusion

The WHO SAM criteria are vital for identifying and treating severe acute malnutrition, particularly in children. Using low WHZ, low MUAC, and bilateral pitting oedema provides reliable assessment tools. An integrated approach ensures more at-risk individuals are identified, allowing for timely care. Applying these diagnostic criteria is a public health priority.

Frequently Asked Questions

The primary significance of the SAM criteria is to provide a standardized, reliable method for health workers to identify individuals with severe acute malnutrition for timely intervention.

MUAC is measured using a tape around the mid-point of the upper arm. For children 6–59 months, a measurement below 115mm indicates severe acute malnutrition.

A WHZ of less than -3 standard deviations means a child's weight for their height is significantly lower than a healthy reference population, indicating severe wasting.

Bilateral pitting oedema is checked by applying thumb pressure to the top of both feet for three seconds. The presence of an indentation confirms this clinical sign.

The criteria for children aged 6–59 months (MUAC <115mm, WHZ < -3 SD, bilateral pitting oedema) are most common. Criteria for infants under 6 months differ.

Research shows MUAC and WHZ identify partially different populations of severely malnourished children, both at high risk of death. Using both improves detection.

After identification, a child is assessed for complications and appetite. Treatment may be outpatient with RUTF or inpatient at a stabilization center.