Mid Upper Arm Circumference (MUAC) is a simple, non-invasive method for rapidly assessing a person’s nutritional status, especially in communities with limited resources or during humanitarian emergencies. This measurement provides a proxy indicator for the body’s energy reserves by quantifying the amount of muscle and subcutaneous fat in the upper arm. The ease of use and portability of the measuring tool make MUAC a practical and highly effective screening method for identifying individuals who require immediate nutritional support or medical intervention.
Defining the Mid Upper Arm Circumference Measurement
Mid Upper Arm Circumference is an anthropometric measurement that serves as a direct indicator of acute malnutrition, also known as wasting. It is highly correlated with the body’s soft tissue mass, consisting mainly of peripheral muscle and fat reserves. A reduction in MUAC reflects a recent and severe depletion of these reserves, signaling a nutritional crisis.
Physiologically, the arm’s circumference changes rapidly in response to short-term changes in nutrient intake and disease. Muscle tissue and subcutaneous fat are metabolized for energy during a severe energy deficit. Because MUAC captures both muscle and fat mass, it provides a powerful snapshot of the body’s capacity to withstand illness and nutritional stress. A decreased MUAC measurement is therefore a strong predictor of increased risk for illness and mortality.
Standard Measurement Technique
The assessment of MUAC requires a specialized, non-stretchable measuring tape, often color-coded and graduated in millimeters. To begin, the individual’s non-dominant arm should be bent at the elbow to form a 90-degree angle. The measurer must locate the precise midpoint of the upper arm between two bony landmarks: the tip of the shoulder (acromion) and the point of the elbow (olecranon process).
The distance between these two points is measured, and the midpoint is marked clearly on the skin. The arm is then gently straightened and allowed to hang relaxed by the side. The tape is wrapped around the arm at the marked midpoint. Ensure the tape is snug against the skin but not so tight that it compresses the underlying tissue. The measurement is read in millimeters where the tape overlaps, providing the final MUAC value.
Interpreting Nutritional Status
The numerical result is translated into clinical categories using standardized thresholds established by global health organizations.
Healthy Status
For young children, a measurement of 125 millimeters or greater (≥125 mm) suggests a healthy or well-nourished status. This value is typically associated with the green color band on the measuring tape. Individuals in this range do not require immediate nutritional intervention.
Moderate Acute Malnutrition (MAM)
A MUAC reading between 115 millimeters and less than 125 millimeters (≥115 mm and <125 mm) indicates Moderate Acute Malnutrition (MAM). This range is commonly represented by the yellow color band and signifies increased nutritional risk. These patients require supplementary feeding and close monitoring to prevent their condition from worsening.
Severe Acute Malnutrition (SAM)
A measurement less than 115 millimeters (<115 mm) is the threshold for Severe Acute Malnutrition (SAM), often marked by the red color band. A value in this range signifies a life-threatening condition. SAM requires immediate referral for intensive therapeutic feeding and medical care. Low MUAC strongly predicts higher mortality risk, making rapid identification and intervention paramount.
Target Populations for MUAC Screening
MUAC is a preferred screening tool for demographic groups where acute malnutrition poses the highest threat. The primary target population is children aged 6 to 59 months, as MUAC is a stronger predictor of mortality risk in this age group than other anthropometric measures. Its simplicity allows for rapid, high-volume screening in community settings, enabling swift identification and treatment initiation.
Screening also extends to pregnant and lactating women, particularly in areas facing food insecurity, where maternal malnutrition can severely impact fetal development and infant health. MUAC is also frequently used in adult populations during humanitarian crises or in refugee camps. It serves as an easily obtainable, immediate measure of nutritional status when traditional tools, like calculating Body Mass Index, are impractical. A common cutoff point for non-pregnant adults is often considered to be around 235 millimeters (23.5 cm) to 250 millimeters (25.0 cm) to screen for underweight.