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Transcutaneous Electrical Nerve Stimulation (TENS)

General Information

TENS is widely used in the treatment of pain. This page contains some extracts from the information booklet that we have written for use in the Pain Clinic.  This information booklet can also be downloaded here, and our nurses have recently produced a short video on the use of TENS which has proved popular with patients, and which is linked here.

How does TENS work?

Transcutaneous Electrical Nerve Stimulation (TENS) is a technique of treatment of pain that dates back to Roman times. In AD 46 electrical treatment (with electric eels!) was used to relieve headache and gout.

Today technology has moved on and TENS units have been found to be helpful for specific painful conditions. TENS is widely used throughout the world. For example, there are an estimated 450,000 users annually in Canadian state hospitals, while in Scandinavia, TENS is well known as a treatment for period pains. In the UK, women in labour are the main group to try TENS, as it is recommended as a safe and effective treatment for labour pain.

The units are small battery operated devices, about the size of a pack of cards, and can be worn during normal gentle daily activity. The device is connected by wires to sticky pad electrodes that are placed on the skin in the area of the pain. This allows a small low intensity electric charge to be passed across the area.

TENS provides pain relief by preventing pain signals from reaching the brain. It can be thought of as a powerful electrical version of “rubbing it better”. The unit, when switched on, stimulates skin nerves and produces a pleasant tingling sensation under the electrodes. This stimulation makes the body make its own painkilling chemicals, enkephalins and endorphins in the spine and brain, reducing or preventing the feeling of pain, thus making use of the Gate Control theory of pain.

Though there is some debate as to how effective TENS is for various types of pain, many patients do find it very helpful. It also has the considerable psychological and convenience benefit that it is something that the patient can use for themselves, thus giving the opportunity for self-efficacy .

Using your TENS machine

The TENS unit produces a safe electrical pulse that stimulates to the nerves by means of two electrodes which stick to the skin. It is easy to operate and maintain. Generally it is most effective to position the electrodes so that the “tingles mix into the area of the pain”.

Starting to use your TENS

  • Make sure that all the control knobs are turned off.
  • Insert a 9 volt battery into the battery compartment.
  • Insert the plug end of the lead wires into the output in the stimulator. Place the other end of the lead wires into the electrodes.
  • Before placing the electrodes on your skin, the area should be clean and non greasy.
  • Place the electrodes on the appropriate area. The idea is that, once the machine is on, the tingles should mix into the painful area.
  • Turn the stimulator on slowly by rotating the intensity control in a clock-wise direction. A light will come on. Continue to rotate the intensity control until you reach the setting that produces a gentle, comfortable tingling sensation. Increase the stimulation power until the tingling is a little stronger than is comfortable, then reduce it slightly until the stimulation is strong but comfortable. The stimulation should not be painful.
  • Failure of the light to come on indicates that the battery needs to be replaced.
  • We normally suggest that you start by using the machine for an hour twice a day. If helpful, it is quite safe and appropriate to increase the time you use it. Frequently pain relief improves with time, and certainly it is best to use it for at least 30 minutes at a time.
  • Pain relief varies from patient to patient. Some people experience pain relief throughout the day by stimulating for only 2 hours a day. Others may need to use their stimulators all the time.
  • It is quite safe, and indeed desirable, to use TENS during your normal activities rather than feeling that you should only use it sitting or lying still.

 Note:  Some TENS machines have timers that cut out after about 15 minutes.  The evidence is that you need longer than this - about 30 minutes to an hour or so.  If you are using one of these machines it is worth using it for more than one of the 15 minute cycles at a time to allow this treatment duration.

Care of your stimulator

The stimulator must not be allowed to get wet. Do not use it in the shower or bath.

If the stimulator is not being used for some months, remove the batteries.

Care of connecting leads

Check that the plugs and pins are satisfactory. Occasionally corrosion can occur: if this happens return them for replacement.

Care of Self-adhesive gel electrodes

Ensure that these are replaced on the plastic sheet and put into a plastic bag between use to keep them moist and sticky. Re-usable self-adhesive pads may be rejuvenated by rubbing a little tap water into the gel surface.

Care of your skin

Skin irritation can occasionally occur under the electrode site.

In order to minimise the possibility of skin irritation the following steps are suggested:

  • Ensure that the skin surface is clean before and after use of the electrodes.
  • Keep the electrodes themselves clean.
  • Make minor location changes of electrodes if irritation develops. This can be done by changing the sites on alternate days.
  • Make sure that the electrodes are firmly attached to the skin. If not, stimulation will be poor and you may feel unpleasant “electric shocks”, and increased skin irritation may occur.

If the above does not relieve any skin irritation discontinue use and consult the doctor or nurse specialist.


TENS treatment should not be used for any new pain without first consulting your doctor.

  • Never place electrodes on the front of the neck – it can stimulate the nerves that control blood pressure with dangerous results, or cause contraction of the laryngeal muscles.
  • Consult your doctor on continued use of the TENS machine if you are pregnant.
  • TENS should never be used by a patient with a pacemaker, cochlear implant, implantable defibrillator-cardioverter or implanted insulin pump.
  • The electrodes should not be used in an area where the skin is numb (eg in nerve injuries) as there could be a possibility of burns. It is recommended not to use TENS overlying a joint replacement.
  • We advise that you do not use TENS while driving: if you have loose electrode contacts a sudden electrical ‘twinge’ might make you jerk the wheel with dangerous results!
  • You should never offer trials of your machine to your friends or relatives.


The most common problem arises from failure to change the battery or failure to wear the electrodes as directed. If no stimulation occurs, the possible causes are as follows:

  • Flat battery - remove and replace.
  • Battery not properly connected.
  • Wires broken - replace.
  • Loose connection - check that the electrode wires are firmly secured in the stimulator and in the electrodes.
  • Worn electrodes.

 Increasingly, nowadays, TENS electrodes can be readily obtained at chemists and some supermarkets as well as from Amazon and other suppliers.


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Pain Service Website, Gloucestershire Hospitals NHS Foundation Trust
Webmaster Dr J G de Courcy, Consultant in Pain Medicine and Anaesthesia
email: pain.webmaster[at]

Page updated 15/3/17