What is the MUAC used to evaluate?: A Guide to Mid-Upper Arm Circumference

October 23, 2025 •

4 min read

According to UNICEF, malnutrition contributes to nearly half of all deaths in children under five annually. In response, healthcare and humanitarian workers rely on simple, fast, and effective screening methods, such as the mid-upper arm circumference (MUAC), to evaluate nutritional status, particularly in resource-limited settings.

Quick Summary

Mid-Upper Arm Circumference (MUAC) measurement is a fast, simple, and reliable method used to assess nutritional status. It screens for acute malnutrition in both children and adults and is also used to predict mortality risk in high-risk populations.

Key Points

Screening for Acute Malnutrition (Wasting): MUAC is primarily used to screen for and classify acute malnutrition, or wasting, in both children and adults using color-coded or graduated tapes.
Predicting Mortality Risk: Low MUAC is a powerful predictor of increased morbidity and mortality, making it a valuable prognostic tool for identifying high-risk individuals.
Assessing in Field Settings: Its simplicity and portability make MUAC ideal for rapid nutritional screening in resource-limited settings, emergencies, and community-based programs.
Use with Immobile or Edematous Patients: MUAC is particularly useful when weight-based measurements like BMI are unreliable or impossible to obtain, such as in patients with fluid retention or mobility issues.
Assessing Overnutrition: Beyond undernutrition, MUAC can also be used as a screening tool for overweight and obesity in adolescents and adults, offering a simple alternative to BMI.
Complementary to Other Assessments: MUAC is a screening tool, not a complete diagnostic, and works best when used with other indicators like bilateral edema or weight-for-height measurements to provide a comprehensive nutritional picture.
Inexpensive and Accessible: Requiring only an inexpensive, non-stretch tape, MUAC is a highly accessible method for nutritional assessment that can be used by trained community health workers and caregivers.

The Science Behind MUAC Measurement

Mid-upper arm circumference, commonly known as MUAC, is a measurement of the girth of a person's upper arm at its midpoint. This measurement reflects the sum of muscle and subcutaneous fat tissue in the arm, providing a snapshot of the body's protein and energy reserves. Its efficacy lies in its simplicity and direct correlation with nutritional status. The measurement is typically taken on the left arm of a relaxed subject, at the halfway point between the tip of the shoulder (acromion process) and the tip of the elbow (olecranon process). For children, specialized color-coded tapes are often used, which allows for quick visual interpretation of the results.

How MUAC Tapes Work

The color-coded MUAC tapes are especially useful in field settings, as they require minimal training and no calculations. The colors typically represent the following nutritional statuses:

Green: Normal nutritional status.
Yellow: Moderate acute malnutrition (MAM).
Red: Severe acute malnutrition (SAM).

This simple, visual method enables community health workers and even caregivers to rapidly identify individuals who are most in need of nutritional support.

The Primary Evaluations Performed by MUAC

MUAC's use extends across various populations and different nutritional conditions.

Evaluating Acute Malnutrition (Wasting)

In children, especially those aged 6–59 months, MUAC is a highly effective tool for identifying acute malnutrition, or wasting. Wasting indicates a recent and severe weight loss, often linked to insufficient nutrient intake or illness. The World Health Organization (WHO) and other organizations use specific MUAC cut-offs to define moderate and severe acute malnutrition. It is an essential component of community-based malnutrition screening, helping to triage children for appropriate treatment.

Assessing Adult Nutritional Status

While famously used for children, MUAC is also a valid tool for assessing the nutritional status of adults. It can be used to screen for both undernutrition (underweight) and overnutrition (overweight and obesity). In contexts where obtaining accurate height and weight measurements is challenging, such as in resource-limited settings or with immobile patients, MUAC offers a practical and reliable alternative to Body Mass Index (BMI).

Predicting Mortality Risk

One of the most critical applications of MUAC is its ability to predict a person's risk of morbidity and mortality. Research has shown a strong correlation between low MUAC measurements and increased risk of death, particularly in children. This makes it a powerful and fast prognostic tool, allowing health professionals to prioritize individuals who need urgent intervention. MUAC has been shown to be a better predictor of mortality than BMI in some adult populations as well.

Assessing Body Composition

Beyond simply classifying nutritional status, MUAC provides information on body composition, specifically the proportion of muscle and fat mass. While it doesn't differentiate between the two without additional measurements like skinfold thickness, its value lies in its reflection of total energy and protein reserves. For individuals with conditions affecting fluid status, such as edema, MUAC is often a more reliable indicator of body composition than weight-based measures.

MUAC vs. BMI: A Comparative Analysis


Feature	Mid-Upper Arm Circumference (MUAC)	Body Mass Index (BMI)
Measurement Tools	Simple, inexpensive tape measure.	Weight scale and stadiometer.
Equipment Portability	Highly portable, ideal for field and emergency settings.	Less portable and requires more setup.
Calculation	Direct reading or visual interpretation (color-coded tapes).	Requires a mathematical calculation ($$weight/height^2$$).
Time/Skill Required	Very fast and requires minimal training.	Can be more time-consuming, requires more training for accuracy.
Reliability with Edema	Less affected by localized fluid retention.	Unreliable due to fluid retention affecting weight.
Target Population	Used for both children and adults.	Widely used for adults, with age-specific curves for children.
Predictive Power	Strong predictor of mortality risk.	Predicts morbidity and mortality, but may not be as effective as MUAC in all contexts.

Limitations and Important Considerations

Despite its advantages, MUAC has limitations. The standard cut-off values can vary by age, sex, and ethnic group, meaning a single universal threshold isn't always accurate. It is a screening tool, not a complete diagnostic assessment, and should be used in conjunction with other indicators like bilateral edema or weight-for-height measurements. In some cases, like Kwashiorkor (protein malnutrition with edema), MUAC alone may not give the full picture. For more precise assessment, especially in clinical settings, MUAC-for-age z-scores are often used to compare a child's measurement to a reference population.

Conclusion

Ultimately, what is the MUAC used to evaluate is the nutritional status of individuals, particularly for rapid screening of acute malnutrition and assessing mortality risk in vulnerable populations. Its practicality, low cost, and ease of use have made it an indispensable tool for public health and humanitarian efforts worldwide. While not a standalone diagnostic instrument, its strategic use, often alongside other indicators, is crucial for identifying those most in need and guiding timely and effective nutritional interventions.

For more information on the implementation and standards of MUAC, authoritative guidelines are available from organizations like UNICEF.

Frequently Asked Questions

MUAC stands for Mid-Upper Arm Circumference. It is a measurement of the circumference of a person's upper arm at its midpoint.

The measurement is taken using a non-stretchable tape measure on the left upper arm. The midpoint between the tip of the shoulder (acromion) and the tip of the elbow (olecranon) is located, and the tape is wrapped around the arm at this point.

MUAC is useful in emergencies because it is a simple, quick, and portable tool that requires minimal training. It allows for rapid and effective screening of acute malnutrition in large populations, helping to prioritize the most vulnerable individuals.

Yes, while it is widely known for child malnutrition screening, MUAC is also used to evaluate the nutritional status of adults and adolescents, including for screening both undernutrition and overnutrition.

MUAC and BMI evaluate different aspects and are often complementary. MUAC is simpler, less resource-intensive, and less affected by fluid retention. However, BMI is a standardized measure that correlates well with body fat. MUAC is often preferred in field settings or for non-ambulatory patients.

Color-coded MUAC tapes provide a simple visual assessment. A measurement in the green zone indicates normal nutrition, yellow indicates moderate acute malnutrition, and red signifies severe acute malnutrition, signaling the need for urgent attention.

The 'Family MUAC' approach is a strategy where mothers and other caregivers are trained to use MUAC tapes to screen their own children for early signs of malnutrition. This empowers communities and improves the early detection and coverage of treatment services.