What Does a Low MUAC Score Mean? A Comprehensive Guide

November 30, 2025 •

3 min read

Millions of children globally are screened for malnutrition using a simple, non-invasive tool called the Mid-Upper Arm Circumference (MUAC) tape, and a low MUAC score can signify serious undernutrition. This measurement is a critical public health indicator used to identify individuals at risk.

Quick Summary

A low Mid-Upper Arm Circumference (MUAC) score indicates poor nutritional status, signaling moderate or severe acute malnutrition in children, adults, and pregnant women.

Key Points

Indicator of Malnutrition: A low MUAC score is a primary indicator of undernutrition or wasting, especially in children and pregnant women.
Age-Specific Cut-offs: Thresholds for low MUAC differ based on age, with specific levels for infants (e.g., <115mm for severe acute malnutrition) and adults (e.g., <24.5cm for underweight).
Health Risks: Low MUAC is associated with serious health risks, including increased mortality, weakened immunity, and impaired growth and development.
Simple Screening Tool: MUAC is valued for its ease of use and low-cost nature, making it an ideal screening tool for large-scale community health programs.
Predictive of Mortality: For acutely malnourished children, a low MUAC is a more reliable predictor of the risk of death than a low Weight-for-Height Z-score alone.
Multiple Causes: A low MUAC can result from food insecurity, frequent infections, poor maternal nutrition, and underlying chronic diseases.

Understanding Mid-Upper Arm Circumference (MUAC)

Mid-Upper Arm Circumference (MUAC) is a simple anthropometric measure to assess nutritional status. Taken at the midpoint of the upper arm, it reflects muscle and fat reserves. MUAC is practical for screening due to its ease of use, minimal equipment needs, and correlation with other nutritional assessments like BMI, especially in resource-limited settings. It helps quickly identify individuals, particularly children, at high risk of poor health outcomes, including death.

Interpreting a Low MUAC Score

Low MUAC scores are interpreted differently based on age and physiological state.

Pediatric Low MUAC Scores

For children aged 6 to 59 months:

Severe Acute Malnutrition (SAM): MUAC below 115mm (often red on tape) indicates high mortality risk and requires immediate care.
Moderate Acute Malnutrition (MAM): MUAC between 115mm and 125mm (yellow) requires supplementary feeding and monitoring.
Normal: MUAC of 125mm or greater (green).

Adult Low MUAC Scores

MUAC screens for adult undernutrition when other measures are difficult. Proposed thresholds include below 25cm for men and 24cm for women, correlating with a BMI under 18.5 kg/m².

Low MUAC During Pregnancy

In pregnant women, MUAC below 23cm indicates poor nutrition, linked to higher risk of low birth weight. Routine antenatal MUAC screening identifies those needing extra nutritional support.

What a Low Score Indicates

A low MUAC signifies depleted muscle and fat reserves, pointing to:

Wasting: Rapid weight loss from poor intake or illness.
Chronic Undernutrition: Long-term poor nutrient intake affecting development.
Increased Mortality Risk: For children, low MUAC predicts death risk better than Weight-for-Height Z-score.

Causes Behind a Low MUAC Score

Low MUAC is often caused by several interacting factors:

Food Insecurity: Lack of adequate nutrition.
Recurrent Infections: Illnesses like diarrhea or pneumonia deplete nutrients.
Poor Maternal Health: Maternal nutrition affects newborn MUAC and growth.
Socio-demographic Factors: Low education or poor sanitation.
Underlying Medical Conditions: Chronic diseases impacting nutrient use.

The Health Risks Associated with a Low MUAC Score

Low MUAC has significant health consequences:

High Mortality Risk: A major predictor of death in children with SAM.
Weakened Immune System: Undernutrition increases susceptibility to infections.
Impaired Growth and Development: Can lead to stunting and poor cognitive outcomes in children.
Adverse Pregnancy Outcomes: Linked to inadequate gestational weight gain and low birth weight.

Measuring MUAC: Process and Considerations

Accurate MUAC measurement uses a non-stretch tape, often color-coded for children:

Find Midpoint: Locate the midpoint between the shoulder and elbow on the non-dominant arm.
Wrap Tape: Wrap the tape around the midpoint with the arm relaxed.
Read Measurement: Read the score in millimeters; the tape should be snug but not tight. Proper training is key for accuracy.

Improving a Low MUAC Score

Improving a low MUAC requires addressing underlying causes:

Nutritional Support: Providing nutrient-rich foods, RUTF, and supplements.
Improved Diet: Ensuring a balanced intake of macro and micronutrients.
Infection Management: Timely treatment of illnesses.
Maternal and Child Health: Promoting maternal nutrition, breastfeeding, and proper feeding.
WASH Interventions: Improving hygiene to reduce infections.

MUAC vs. Weight-for-Height Z-Score (WHZ): A Comparison

MUAC and WHZ both assess acute malnutrition but differ in use.


Feature	MUAC	WHZ
Ease of Use	Very easy and quick.	More complex, requires accurate measurements and growth charts.
Equipment	Simple, inexpensive tape.	Requires scales and height board.
Screening Context	Ideal for rapid community screening.	Gold standard for clinical diagnosis in health facilities.
Indicator	Primarily reflects muscle and fat mass, immediate indicator of wasting.	Compares weight to height standard, broader measure of wasting.
Predictive Power	More sensitive for identifying children at highest risk of death.	Can miss some at-risk children identified by MUAC.

Conclusion

A low MUAC score indicates moderate or severe acute malnutrition and its interpretation varies by age. Causes are often multiple, involving poor diet, infection, and socioeconomic factors. Associated health risks are severe, including increased mortality and impaired development. As MUAC is a simple and effective screening tool, early detection allows for timely intervention. Understanding what a low MUAC score means is vital for combating malnutrition globally. Consult WHO resources for detailed clinical guidelines.

Frequently Asked Questions

For children aged 6 to 59 months, a normal MUAC score is 125mm or greater. A score between 115mm and 125mm indicates moderate acute malnutrition, while less than 115mm indicates severe acute malnutrition.

Yes, MUAC can be used for children, adults, and pregnant women. However, the interpretation and specific cut-off points for malnutrition differ depending on the age and physiological state.

MUAC is a measure of muscle and fat reserves, particularly useful for rapid screening in resource-limited settings and for predicting mortality risk in acute malnutrition. BMI (Body Mass Index) requires accurate height and weight measurements and is considered a broader, population-level measure of nutritional status.

Yes. A person, particularly an adult, can have a seemingly normal weight but still have a low MUAC. This can indicate a loss of muscle mass, which MUAC is effective at detecting, especially in older adults or those with chronic diseases.

For a pregnant woman, a MUAC score below 23cm is a marker of poor nutritional status and is associated with a higher risk of adverse birth outcomes, including having a low birth weight baby.

The first step after receiving a low MUAC score is to seek a full medical and nutritional assessment. A low score indicates a need for intervention, such as supplemental feeding, treatment for underlying illness, and nutritional counseling.

Yes, with proper training, caregivers can be taught to use simple, color-coded MUAC tapes to screen for malnutrition at home, helping to facilitate earlier detection and treatment.

While it can vary by population, a commonly cited MUAC cut-off point for indicating adult underweight (BMI <18.5) is 24.5 cm.