Understanding Nutrition Diet: What is the instrument used to measure mid-upper arm circumference?

October 23, 2025 •

3 min read

According to UNICEF, millions of children suffer from acute malnutrition globally, highlighting the need for effective, easy-to-use screening tools. A key tool in combating this is the specific instrument used to measure mid-upper arm circumference (MUAC), known as a MUAC tape.

Quick Summary

The mid-upper arm circumference (MUAC) tape is a color-coded or non-coded plastic strip used to quickly and effectively screen for acute malnutrition, especially in children aged 6–59 months and pregnant women.

Key Points

MUAC Tape: The primary instrument is a simple, non-stretchable tape, often color-coded, for measuring mid-upper arm circumference.
Screening Tool: MUAC tapes are primarily used as a screening tool to quickly assess for acute malnutrition, especially in children and pregnant women.
Color-Coded Interpretation: The red, yellow, and green zones on a child's MUAC tape correspond to severe, moderate, and adequate nutritional status, respectively.
Portable and Practical: MUAC tapes are highly portable and require minimal training, making them ideal for field assessments and community health workers.
Complements BMI: While MUAC correlates with BMI, it is a superior alternative when height and weight measurements are challenging, such as with bedridden patients or those with edema.
Identifies Mortality Risk: MUAC is particularly effective at identifying children who are at a higher risk of death from malnutrition.
Limitations: The tape has limitations and should not be used as a sole diagnostic tool, as it can sometimes disagree with other metrics and doesn't capture all forms of malnutrition.

Introduction to Nutritional Assessment

Nutritional assessment is a critical component of public health and individual wellness. While Body Mass Index (BMI) is a common metric, it can be impractical in many settings, such as remote areas or for bedridden patients. For this reason, healthcare workers and humanitarian aid organizations utilize simple, portable, and effective tools to quickly identify individuals at risk of malnutrition. One such tool, the Mid-Upper Arm Circumference (MUAC) tape, offers a non-invasive and rapid method for assessing nutritional status. It is especially effective in identifying acute malnutrition, which reflects recent or rapid weight loss.

The Mid-Upper Arm Circumference (MUAC) Tape

The instrument used to measure mid-upper arm circumference is a special measuring tape called a MUAC tape. It is sometimes referred to as a Shakir Strip. These tapes are made from a non-stretchable, flexible plastic material and are designed for simplicity and accuracy. Many MUAC tapes for children feature a color-coded system to provide an immediate visual indication of nutritional status. Different tapes are used for children, adults, and pregnant women to ensure appropriate measurements.

How to Take an Accurate MUAC Measurement

Accurate MUAC measurement is crucial for reliable results. The standard procedure involves locating the midpoint of the upper arm between the shoulder and elbow, wrapping the tape snugly but not tightly at this point, and reading the measurement where the tape overlaps through the window. For color-coded tapes, the window also visually indicates the nutritional status zone.

The Role of MUAC in Nutritional Assessment

MUAC measurement is a powerful and practical tool for several reasons. Its portability and ease of use make it ideal for resource-limited settings and large-scale community screenings. It is highly effective at identifying children at the highest risk of mortality due to severe acute malnutrition (SAM). With minimal training, community health workers or caregivers can accurately use the tape. MUAC is a sensitive indicator of acute weight loss, particularly useful for children aged 6 to 59 months and pregnant women.

MUAC vs. Body Mass Index (BMI): A Comparison

MUAC and BMI are both valuable tools, but serve different purposes. MUAC is especially useful when BMI cannot be measured accurately due to logistical challenges or patient conditions. The table below highlights key differences.


Feature	Mid-Upper Arm Circumference (MUAC)	Body Mass Index (BMI)
Equipment	Simple, low-cost plastic tape	Weighing scale and stadiometer
Portability	Highly portable	Less portable
Ease of Measurement	Quick and simple, minimal training	More steps, can be challenging
Best Use Case	Mass screening, bedridden patients	Standard clinical assessment
Fluid Retention Impact	Less affected by edema	Can be significantly skewed by edema
Identifies Risk of Mortality	Strong predictor of mortality risk in children	Correlates with nutritional status, not a direct predictor of mortality in the same context

Interpreting MUAC Measurements

Interpretation of MUAC measurements relies on specific cut-off points based on age and population. For children aged 6 to 59 months using a color-coded tape, red indicates severe acute malnutrition (<11.5 cm), yellow indicates moderate acute malnutrition (11.5 cm to <12.5 cm), and green indicates adequate nutritional status (≥12.5 cm). Low MUAC in adults correlates with a higher risk of malnutrition. For pregnant women, a MUAC below 24 cm may indicate acute malnutrition.

Limitations and Nuances of MUAC

While valuable, MUAC is a screening tool and doesn't provide a complete picture of nutritional health. Its sensitivity can vary, and it may not always align perfectly with other metrics like Weight-for-Height Z-scores. MUAC also doesn't specify the type of malnutrition, such as kwashiorkor. It should be used as part of a broader nutritional assessment for a comprehensive diagnosis. However, its practicality and effectiveness in identifying high-risk populations make it indispensable for public health.

Conclusion

The MUAC tape is the instrument used to measure mid-upper arm circumference and is a simple yet highly effective tool for nutritional screening. Its ease of use, portability, and low cost make it vital for detecting and managing malnutrition, particularly in children and pregnant women in resource-limited areas. By enabling timely identification of individuals at risk, MUAC plays a critical role in global public health. Despite some limitations, its utility as a rapid screening instrument is significant.

UNICEF provides resources and technical information on MUAC tapes to support global efforts against malnutrition.

Frequently Asked Questions

The instrument used to measure mid-upper arm circumference is a special, non-stretchable measuring tape commonly known as a MUAC tape or Shakir Strip.

MUAC screening is commonly used for children aged 6 to 59 months, pregnant women, and other adults, particularly in resource-limited settings where standard measurements are difficult.

On a child's MUAC tape, red indicates severe acute malnutrition, yellow indicates moderate acute malnutrition, and green indicates an adequate nutritional status.

Yes, there are specific MUAC tapes for adults, which may or may not be color-coded. A low MUAC measurement in an adult can indicate malnutrition.

MUAC is simpler and more portable than BMI. It correlates positively with BMI but is particularly useful in situations where weight and height cannot be measured accurately, such as in emergency or field settings.

While primarily used for undernutrition, MUAC has shown some effectiveness in screening for overweight or obesity, though BMI is a more widely used indicator for this.

MUAC has a few limitations, including varying sensitivity depending on the population, a lack of insight into the specific cause of malnutrition, and potential disagreement with other anthropometric measures.

The main benefits of MUAC tapes are their low cost, portability, and simplicity. They are highly effective for mass screening and can identify those at the highest risk of mortality.