How to use a tens machine? General Recommendations

A TENS machine is a great, safe and non-invasive way to provide effective pain relief without the use of any hazardous drugs. TENS stands for transcutaneous electrical nerve stimulation.  The way these electric impulses are sent to the nerves is by using one or more electrodes directly on the skin. 

The main purpose of a TENs machine is to somehow disrupt the normal pain cycle by giving the body a stimulation to the skin around the pain site. What this causes is it sends tiny electrical impulses to our brains. These impulses travel faster that the pain impulses along your spinal cord. When it receives the impulses coming from the electrodes, the brain can only process a limited amount of information so it will not be able to process the pain signals that are coming in at a much slower pace.
Now, it should be pointed out that the TENS machine effectiveness as a viable pain relief system is still an issue that is being debated by specialists. This is mostly because its results can vary from person to person, even between people suffering from the same condition, so a TENS machine might not be exactly for everybody, but those who find comfort on using the machine find it most convenient as its soothing and largely without any side-effects.

They way you use a TENS machine is rather simple, but please be advised to consult with your physician first, specially if you have a pacemaker or if you are on the first weeks of pregnancy. Please ask your physician for instructions on how to apply the electrodes on the areas afflicted with pain, follow his or her instructions closely and also.
The electrodes are to be placed straight on the skin of the area in pain. They are to be used at specific amounts of time that your physician will decide for you. The skin on which the electrodes are being applied needs to be clean and dry before use. They can be combined with other pain treatments, and in some cases can be used to diminish the amount of pain-killers taken for patients going through pain. 
General recommendations when using a TENS machine are the following:
Before you place any electrode on the skin, please make sure that the machine is turned off. The skin needs to be dry and clean, also the skin must not have any irritation, cuts or lesions. You can use the electrodes with tape to the skin for more secure placing. Once the electrodes are in place you can turn on the machine and gradually turn it up until you feel a strong, but not unpleasant sensation. The sensation with fade slowly, that means the body is accommodating to it, when this happens the intensity needs to be turn up slightly. After the session is done, you may remove the electrode pads and clean the skin with regular soap and water. Also, it is highly advised that you use the TENS machine while lying down on a comfortable position.

Related Read: How to use a TENS unit for shoulder pain?