What Does MUAC Tell You About Nutritional Status?

November 21, 2025 •

3 min read

According to The Lancet, malnutrition is associated with more than 3 million child deaths every year. Understanding what MUAC tells you is crucial, as this simple and effective tool helps health workers quickly screen for acute malnutrition, enabling timely intervention and saving lives.

Quick Summary

Mid-upper arm circumference, or MUAC, is a measurement for rapidly assessing acute malnutrition in children and adults. It provides a reliable, easy, and cost-effective method for screening nutritional status in public health and humanitarian settings.

Key Points

Rapid Screening: MUAC is a fast, reliable, and cost-effective method for screening large populations for acute malnutrition, especially in crisis situations.
High-Risk Identification: The measurement is a powerful predictor of mortality risk in severely malnourished children, identifying those most in need of urgent intervention.
Child-Focused Tool: While used for adults, MUAC is most effective and standardized for children aged 6 to 59 months, where a color-coded tape provides instant visual results.
Indicator of Body Composition: MUAC measures the circumference of the upper arm, which reflects the combined mass of muscle and subcutaneous fat.
Supports Broader Assessment: MUAC is a screening tool, not a complete diagnosis, and should be used alongside clinical judgment and other anthropometric data.
Empowers Community Health: Its simplicity allows health workers with minimal training to conduct screenings, broadening access to nutritional assessments in hard-to-reach areas.

Understanding the MUAC Measurement

Mid-upper arm circumference (MUAC) is a simple measurement taken at the midpoint of the upper arm, between the shoulder and elbow. It estimates the amount of muscle and fat in the arm, indicating overall nutritional status. Its portability and low cost make it ideal for widespread screening, particularly in areas with limited resources. For children aged 6 to 59 months, MUAC is especially useful as an age-independent screening tool for severe malnutrition, important when birth dates aren't known. Color-coded MUAC tapes simplify interpretation with red, yellow, and green sections corresponding to different nutritional statuses. UNICEF and other organizations have standardized these tapes for various populations.

How to Take an Accurate MUAC Measurement

Correct technique is vital for accurate MUAC readings:

Use a flexible, non-stretchable MUAC tape.
Position the subject's left arm loosely bent at the elbow.
Mark the midpoint between the shoulder (acromion) and elbow (olecranon).
Wrap the tape around the arm at this midpoint while the arm hangs loosely.
The tape should be snug but not compress the arm.
Record the measurement to the nearest millimeter.

Interpreting MUAC Color Codes and Cut-Offs

Interpreting MUAC depends on age and specific cut-off points, often based on WHO guidelines. Color codes on tapes provide quick visual assessment.

For Children (6-59 months):

Green: MUAC 12.5 cm or greater, suggesting normal nutrition.
Yellow: MUAC between 11.5 cm and 12.5 cm, indicating Moderate Acute Malnutrition (MAM).
Red: MUAC less than 11.5 cm, a sign of Severe Acute Malnutrition (SAM) and high mortality risk.

For Adults:

Numerical cut-offs are used as color-coded tapes are less common.
Over 32 cm suggests possible obesity (BMI > 30 kg/m²).
Less than 23.5 cm suggests possible underweight (BMI < 20 kg/m²).
For pregnant women, less than 17 cm indicates severe malnutrition, 17-21 cm indicates moderate malnutrition.

MUAC vs. Other Nutritional Indicators


Feature	MUAC	Weight-for-Height Z-Score (WHZ)	Body Mass Index (BMI)	Clinical Judgement
Primary Purpose	Rapid screening for acute malnutrition in children aged 6-59 months, as well as pregnant women and adults.	Diagnostic standard for wasting (acute malnutrition) in children.	Diagnostic tool for underweight, overweight, and obesity in older children and adults.	Assessment based on physical signs, symptoms, and medical history.
Equipment	Simple, portable, color-coded tape.	Calibrated scales, stadiometer, reference charts/software.	Calibrated scales, stadiometer, reference charts/software.	Clinical observation, conversation, and examination.
Skills Needed	Minimal training, easy to perform.	Requires trained personnel, meticulous technique, and accurate age/height data.	Requires trained personnel and accurate height/weight data.	Relies heavily on medical expertise and local knowledge.
Time/Cost	Fast and inexpensive for mass screening.	Slower, more expensive, and complex, but highly accurate.	Similar to WHZ, can be time-consuming.	Highly variable, depends on skill and context.
Portability	Excellent, can be used anywhere.	Poor, equipment is bulky and difficult to transport.	Poor, equipment is bulky and difficult to transport.	Excellent, relies on the clinician's eyes and ears.

Why MUAC is a Crucial Tool

MUAC is a strong predictor of mortality risk in malnourished children, complementing other measures. It's effective at identifying high-risk children, even if other metrics like WHZ don't show severe malnutrition. This makes it essential for humanitarian groups like MSF and UNICEF in quickly identifying vulnerable children in emergencies. Its simplicity allows trained community health workers to conduct large-scale screenings, expanding health intervention reach. Color-coded tapes empower caregivers to monitor children's nutritional status at home, enabling early detection and intervention.

Limitations and Considerations for MUAC

MUAC is a valuable screening tool but has limitations. It's not a full diagnostic and should be part of a comprehensive assessment including clinical examination.

Key limitations:

Variability: Performance can differ by gender and age, requiring specific cut-offs.
Incomplete Detection: It may not detect all forms of malnutrition, particularly with edema, which can falsely elevate the reading.
Tape Inconsistency: Historical tape variations are being addressed by standardization efforts from organizations like UNICEF.
Age Sensitivity: While effective for children aged 6-59 months, it is less precise for older children.

Conclusion

MUAC is a powerful, simple screening tool providing immediate insight into nutritional health, especially for vulnerable populations. Its ability to quickly identify acute malnutrition and mortality risk makes it crucial for humanitarian and public health programs. Although not a standalone diagnostic, MUAC data enables rapid, life-saving interventions for those most in need.

Visit the UNICEF Supply Division website for detailed technical bulletins on MUAC tapes.

Frequently Asked Questions

The primary purpose of MUAC screening is to rapidly identify and triage individuals, particularly children and pregnant women, who are suffering from or are at high risk of acute malnutrition, allowing for immediate life-saving interventions.

The colors indicate the child's nutritional status: Green signifies a normal nutritional status, yellow indicates moderate acute malnutrition (MAM), and red points to severe acute malnutrition (SAM).

Yes, MUAC can also be used for adults, especially pregnant women and the elderly, to provide an estimate of their nutritional status when other measurements like BMI are not practical.

MUAC is primarily a screening tool for identifying at-risk individuals. It is part of a larger nutritional assessment and does not provide a complete diagnosis on its own.

MUAC is less comprehensive than methods like Weight-for-Height Z-score (WHZ) but is considered a 'very good' test for its diagnostic accuracy in detecting acute malnutrition within its intended use, especially for predicting mortality risk.

The measurement is taken at the midpoint of the left upper arm, between the shoulder tip (acromion) and the elbow tip (olecranon process), using a non-stretchable tape. The tape should be snug but not tight.

Limitations include its inability to detect all forms of malnutrition (like kwashiorkor, which can cause swelling), and the fact that its effectiveness can vary by age, sex, and population, sometimes missing cases identified by other indicators.

In emergency situations, MUAC's speed, portability, and ease of use enable health workers to quickly screen and prioritize a large number of people for admission into feeding programs, effectively saving lives.