What are Class III Approved scales?

It can be incredibly difficult to know which medical weighing scale to buy with so many different terms and accuracies mentioned.

What do M and CE stand for, and what does Class III Approved mean? We intend to clear these up for you in this blog post.



Why are accurate scales important?

When obtaining a weight for monitoring, diagnosis or treatment of patients, it’s vital that the weighing scales used are accurate and reliable. For instance, most drug dosages are based on the weight of a patient, so an inaccurate weight can lead to an incorrect dosage – and this can be fatal.

Incidents where patients had been incorrectly diagnosed, or given the wrong drug dosage, led to the introduction of regulation – the NAWI Directive.

What is the NAWI Directive?

NAWI stands for Non Automatic Weighing Instrument. Since January 1st 2003, the NAWI Directive has defined the legal requirements for weighing scales in the EU used for 'the determination of mass in the practice of medicine for weighing patients for the purpose of monitoring, diagnosis and treatment.'

Medical scales purchased before January 1st, 2003 can still be used, but replaced with a Class III Approved equivalent as soon as conveniently possible.

Some scales do not require approval, such as bathroom scales you use at home. They are not required by law to be accurate, and this is why they can be produced at such low costs. Gyms can also use non-approved scales, if they wish. As for retail and industry, a Class III Approved scale (which in this case may be referred to as a Trade Approved scale) does not need to be used, unless it is used for buying or selling an item based on weight.

What are Class III Approved scales?

Under the NAWI Directive, scales are ordered by class. Class I scales are the most accurate; used for precise weighing where there is very little or no room for error. Most applications do not need Class I, or Class II scales; for most medical applications, a Class III Approved scale is suitable.

When should a Class III Approved medical scale be used?

Class III weighing scales should be used to determine weight and Body Mass Index (BMI), for any medication, treatment, diagnosis or monitoring. To ensure that they’re correctly calibrated, they should be checked regularly (at least every 12 months is recommended) and routinely maintained. Any scales not giving accurate readings should be removed immediately.

How is a scale verified?

In order to be approved, these scales undergo a Verification Test; this puts the scales through a number of demanding tests to evaluate whether it is accurate enough to earn its Class rating. These tests focus on performance and repeatability to ensure that the scale provides accurate results every time.

The tests involve placing a weight on the scale, and removing it, multiple times. If the scale falls below the 'minimum' accuracy allowed during these tests, it cannot pass (or be 'stamped,' as it is also known).

These tests can only be carried out by a governmental body or recognised authority.

What do the different symbols mean?

Approved scales are marked with a number of symbols to show that they have passed their Verification Test. These include:

  • CE - this is the manufacturer's declaration that their scale meets the requirements of the applicable EC laws.
  • M - this is the manufacturer's declaration that their scale meets NAWI directives.
  • An identification number - This 4 digit number identifies the body who authorised the scale. 

When ordering a scale, ensure that they have all three of these symbols to know that you’re buying a certified scale.

Further Reading

The National Measurement Office released a great video about Class III weighing scales featuring our weighing scales, which you can view here.

Have you ever wondered how accurate your scales need to be? Well here’s your answer.

Regular service and calibration checks are recommended for Class III Approved medical scales. Read 5 benefits of service contracts for medical weighing scales.

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