What is the purpose of measuring mid-upper arm circumference?

October 22, 2025 •

4 min read

According to The Lancet, more than 3 million child deaths every year are associated with malnutrition, underscoring the vital need for rapid and reliable screening methods. In this context, understanding what is the purpose of measuring mid-upper arm circumference (MUAC) is crucial for identifying and treating acute malnutrition, especially in vulnerable populations and resource-limited settings.

Quick Summary

The mid-upper arm circumference (MUAC) measures nutritional status by assessing arm muscle and fat mass. It is a quick and simple screening tool, particularly effective for identifying acute malnutrition and predicting mortality risk in children and adults in resource-limited areas.

Key Points

Rapid Screening: MUAC is a quick and simple way to screen for acute malnutrition, particularly in children and vulnerable populations, without complex equipment.
Predicting Mortality: A low MUAC reading is a strong predictor of mortality risk, enabling health workers to identify and prioritize the most severe cases.
Monitoring Intervention: Serial MUAC measurements are used to monitor a patient's response to nutritional treatment and track their recovery over time.
Indicator of Body Reserves: MUAC measures the sum of muscle and fat tissue in the upper arm, reflecting the body's overall protein and energy stores.
Practical in Field Settings: Its simplicity and ease of use make MUAC an ideal tool for mass screenings in remote areas, clinics, and emergency situations where other equipment is not available.
Complements Other Metrics: MUAC is often used alongside other anthropometric indicators, like weight-for-height z-score, as different methods can detect distinct subsets of malnourished individuals.
Applicable to Various Groups: While primarily used for young children, MUAC is also effectively applied to screen for malnutrition in adults, pregnant women, and individuals with certain medical conditions.

What is MUAC and its significance?

Mid-upper arm circumference, commonly known as MUAC, is a measurement of the girth of the upper arm at its midpoint. It is a simple, inexpensive, and non-invasive anthropometric technique used primarily for assessing a person's nutritional status, with a specific focus on screening for acute malnutrition. By measuring the combined mass of muscle and subcutaneous fat in the arm, MUAC provides a reliable indicator of the body’s protein and energy reserves. This makes it an indispensable tool for public health officials and healthcare workers in emergency situations and community-based programs where traditional measurements like weight and height may be impractical or impossible.

The primary purpose: Screening for malnutrition

The main purpose of measuring MUAC is to serve as an effective screening tool for acute malnutrition, a condition characterized by rapid weight loss or failure to gain weight. Acute malnutrition, also known as wasting, is a significant public health issue, particularly among young children in developing countries. MUAC is especially valuable in this context for several reasons:

Community-level screening: MUAC can be used by minimally trained health workers and even caregivers to screen large numbers of people in communities, refugee camps, and other field settings.
Predicting mortality: Research has shown that low MUAC measurements are strongly correlated with an increased risk of death in malnourished children. This allows healthcare providers to prioritize the most at-risk individuals for immediate intervention.
Monitoring treatment effectiveness: Serial measurements of MUAC over time can be used to track a patient's response to nutritional interventions. An increase in MUAC indicates that the person is gaining back lost muscle and fat tissue, signifying recovery from malnutrition.

How to measure mid-upper arm circumference properly

The procedure for measuring MUAC is straightforward but requires adherence to a few key steps to ensure accuracy.

Select the arm: Use the non-dominant arm. The person's arm should hang relaxed at their side.
Locate the midpoint: Measure the distance between the tip of the shoulder bone (acromion) and the tip of the elbow (olecranon). Mark the midpoint with a pen.
Place the tape: Wrap a non-stretchable measuring tape around the arm at the marked midpoint.
Ensure correct tension: The tape should be snug but not so tight that it compresses the skin.
Read the measurement: Record the measurement to the nearest 0.1 cm, ensuring the numbers are facing the correct way.

For children aged 6 to 59 months, special color-coded tapes (often called Shakir strips) are commonly used. These tapes have color bands for green (normal), yellow (moderate malnutrition risk), and red (severe acute malnutrition), providing an immediate visual interpretation of the child's status.

Use of MUAC in diverse populations

While widely known for its use in assessing young children, MUAC is also valuable for other demographic groups:

Adults: MUAC can serve as an effective proxy for BMI in adults, particularly in resource-limited settings where scales are unavailable or for individuals who are non-ambulatory. Cut-offs for undernutrition and obesity have been established.
Pregnant and postpartum women: MUAC can be used to screen for malnutrition in pregnant women, as it is relatively stable during pregnancy and highly correlated with pre-pregnancy BMI.
Special medical conditions: For hospitalized patients with conditions like heart defects or neurological impairments, where fluid retention or immobility can make weight measurements unreliable, MUAC is a crucial tool for monitoring nutritional status and body composition.

Comparison of MUAC and BMI

While both MUAC and BMI are used to assess nutritional status, they differ significantly in their application and context.


Feature	Mid-Upper Arm Circumference (MUAC)	Body Mass Index (BMI)
Equipment Needed	Simple, non-stretchable tape measure (color-coded for children)	Weighing scale and stadiometer (for height)
Training Required	Minimal training needed for accurate results	Requires more training for precise weight and height measurements
Feasibility	Highly feasible for mass screening in community and remote settings	Can be impractical in field settings or with immobile/edematous patients
Speed	Very fast and easy to perform	Requires more time, especially for measuring height
Indicator for	Body composition (fat and muscle mass) and acute wasting	Overall weight-for-height ratio
Primary Use Case	Rapid screening for acute malnutrition in vulnerable populations	General nutritional status assessment and population-level health monitoring

Limitations and complementary indicators

Despite its benefits, MUAC is not a foolproof diagnostic tool and has several limitations. A MUAC measurement should always be considered alongside other clinical indicators and nutritional assessments. It can have low sensitivity in some contexts, meaning it might miss some cases of malnutrition. Additionally, MUAC and weight-for-height z-scores (WHZ), another standard malnutrition indicator, can identify different groups of malnourished children. For this reason, a comprehensive approach often utilizes multiple anthropometric indicators, such as MUAC, WHZ, and edema status, to provide the most accurate assessment of acute malnutrition. Combining these measurements helps offset the weaknesses of any single indicator, leading to more robust diagnosis and treatment strategies.

Conclusion

In summary, the purpose of measuring mid-upper arm circumference is to provide a rapid, simple, and effective method for screening and monitoring acute malnutrition. Its practical advantages make it a cornerstone of public health interventions, especially in resource-constrained environments. While not a standalone diagnostic tool, MUAC is an invaluable first-line assessment that helps identify at-risk individuals, prioritize treatment, and track recovery. Integrating MUAC with other nutritional assessment methods ensures a comprehensive and accurate picture of a person's nutritional status, ultimately leading to improved health outcomes globally.

Frequently Asked Questions

In resource-limited areas, MUAC is crucial because it requires only a simple, inexpensive tape and minimal training to use effectively. This enables widespread, rapid screening for acute malnutrition in communities where scales and measuring boards might be unavailable.

Yes, MUAC is used for both adults and children. While its use is well-established for children aged 6 to 59 months, specific cut-off points have also been validated for adults, adolescents, and pregnant women to assess nutritional status.

A child's MUAC tape typically uses a color-coded system: green indicates adequate nourishment, yellow suggests a risk of moderate malnutrition, and red indicates severe acute malnutrition (SAM).

To find the correct spot, first locate the tip of the shoulder (acromion) and the tip of the elbow (olecranon). The midpoint between these two points is where the MUAC measurement should be taken.

No, MUAC is not a perfect measure. It has limitations, including varying sensitivity across different populations and the fact that it doesn't account for conditions like edema. Therefore, it is often used as a screening tool in conjunction with other indicators for a more complete assessment.

Yes, regularly measuring MUAC can be an effective way to monitor recovery. An increase in the measurement over time can signify that a person is gaining back lost muscle and fat tissue, indicating a positive response to nutritional therapy.

MUAC measures the circumference of the upper arm to assess muscle and fat mass, making it ideal for rapid field screening. BMI is calculated from weight and height and is generally used for broader population health monitoring. BMI requires more equipment and is less practical for mass screenings than MUAC.