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Multiple Sleep Latency Test

Your doctor would like you to have a Multiple Sleep Latency Test (MSLT). We hope that the following information will help to answer any questions you may have.

What is a Multiple Sleep Latency test (MSLT)?

The test is the standard way to measure your level of daytime sleepiness.

What should I do before the test?

  • Please wash your hair and do not use any hair products (gel, hairspray etc).
  • Take your medication as normal unless otherwise directed by your doctor.
  • Eat as normal.
  • Please bring a list of medication that you take with you.
  • Please wear comfortable, baggy clothes.
  • Do not drink any beverages that contain caffeine.
  • You are welcome to bring a friend or relative to accompany you to your appointment.

What will happen during the test?

A Clinical Physiologist will be performing your test, although staff in training may be present during your investigation. This will be explained at the time of your appointment and consent for this will be discussed with you. It will be necessary for us to obtain consent before your investigation. This will be done at the beginning of the test. Prior to the MSLT test you will typically be required to have a one night nocturnal Polysomnography (NPSG) – please see the patient information leaflet. The electrodes required for this test will already have been positioned for your NPSG. The Clinical Physiologist performing the test will explain each aspect of the test and will be happy to answer any questions you may have. You will be positioned on a comfortable bed for the test. The day will consist of several trials. After each trial you will be given a break, during which we ask you to remain awake. During the trials you will be given the opportunity to fall asleep for a particular length of time.

How will the results of this test assist my consultant?

An MSLT will help your doctor in the diagnosis and management of your complaint or condition.

Are there any risks?

No, there are no reported risks to this test.

Is an MSLT/MWT test painful?

No, this is a painless test.

How long will the test take?

The whole test will last approximately from 9am to 5.30pm. Please bring something with you to keep you occupied in between trials, i.e magazines, newspapers.

A simple meal can be provided by the hospital during the day, however this is only basic so please feel free to bring along your own food/snacks or you can also make use of the hospital café.

What are the consequences of not having an MSLT?

An MSLT is a well established method of helping doctors to diagnose and treat a wide range of medical conditions. Your doctor would not have as complete a picture as they require and hence your diagnosis may take longer and/or your treatment may not be the most appropriate.

Are there any alternative ways of getting the same information that an MSLT provides?

No. There is no alternative test performed at The Walton Centre.

What happens after the test?

After the recording the small electrodes will be taken off with warm water or a solution to dissolve the special glue. You will then be able to go home or back to work and carry on as usual. There are no after-effects from this test. You will not be told any results on the day. The results will go back to your referring Consultant within 2-3 weeks.


Further information about MSLT is available is available from numerous organisations including:

The Brain Charity: or if you live locally call into their library at Neurosupport, Norton Street. Liverpool. L3 8LR

The British Sleep Society: 

If for any reason you are unable to make this appointment or have any specific requirements or questions (before or after the test) please call 0151 529 5602

Patient co-operation is required for the duration, if due to a learning disability you feel more time is needed, please contact the department. In addition we can also provide a visit to the department in advance of the appointment for patients who may require it to familiarize yourself with the surroundings and staff.

We can provide this information leaflet in larger fonts or audio format via email if required, please phone the number above. 

  • Last Updated:
    01 October 2022
  • Review Date:
    01 October 2026
  • Author:
    Neurophysiology Department
  • Summary:

    The test is the standard way to measure your level of daytime sleepiness.

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