The 2021 Ultimate Guide to TENS Units

As TENS units become increasingly more popular for at-home use between office visits, offer patients an opportunity to learn more about these therapy devices and how they may help provide soothing relief. This ultimate guide post will walk patients through everything they need to know about TENS units, including what they are, how to use them, and how to find the best unit for specific discomfort. 

What is a TENS unit?

A transcutaneous electrical nerve stimulation (TENS) unit is a small, battery-operated device used to relieve and manage acute and chronic pain. It is the most common form of electrotherapy, administering mild electric shocks to the body’s affected area through adhesive pads called electrodes. The electrodes are placed on the skin and are typically connected to the TENS unit with lead wires, though wireless options are also available. 

How do TENS units relieve pain?

Put simply, the electric shocks that the TENS unit administers stimulates the body’s nerves. This helps relieve pain in two ways: by releasing endorphins and pain gating.

Endorphin release

Stimulating the body’s nerves can help activate and release endorphins. Endorphins are one of many neurotransmitters or brain chemicals that transmit messages between cells. These signals enable our bodies to function correctly and affect how we perceive the world around us.  

Endorphins, specifically, are released when our bodies experience pain or stress. When released, they reduce pain, make us feel happier, and enhance our immune response. Endorphin release can be achieved with pain medication. But TENS units have the same effect without the risk of addiction or dependence. 

Pain gating

To experience pain and other sensations, our body’s nerve fibers send sensory signals to the spinal cord, which then sends the signals up to our brain so we can perceive the sensation. Large nerve fibers send signals when we experience normal touch or pressure, while small nerve fibers send pain signals when we’re injured. Our ability to perceive pain depends on the brain receiving the pain signals and decoding them into the feeling of discomfort, etc. 

In the early 1960s, Ronald Melzack and Patrick Wall proposed the idea of “pain gating,” or gate control theory. This is the idea that before your brain can receive pain signals; a “pain gate” at the end of the spine allows or blocks the signals from passing through to the brain. For some injuries, the signals pass easily, and we feel intense pain. In other cases, the signals may be inhibited or stopped entirely. 

Activating the large nerve fibers with normal sensations can help inhibit the pain signals sent by the small nerve fibers and help relieve pain. This is why we often rub or shake an injured body part, and why TENS units work! TENS units activate the large nerve fibers by creating a tingling or massaging sensation on the injured area, which blocks pain signals and temporarily reduces our perception of pain. 

How long does the relief last?

After using a TENS unit, pain relief can last anywhere from 5 minutes to 24 hours. It’s hard to say precisely why it varies so much. Still, it’s been suggested that the amount of relief depends on the type and intensity of the pain. For example, someone with acute pain may experience more prolonged periods of relief than someone with chronic pain, who might go back to their normal pain levels shortly after turning off the device. 

Regular use of a TENS unit can sometimes lead to longer relief periods. Over time it can also cause a person to build up a tolerance to the treatment. To prevent the nervous system from getting too accustomed to electrotherapy, it is recommended to take breaks between treatment sessions or change the position of the electrodes. 

TENS Unit vs. EMS

TENS units are not to be confused with EMS (electrical muscle stimulation) devices. However, they are very similar; both portable devices deliver mild electric shocks through electrodes. Each is used for a different purpose.

While TENS units stimulate the nerves, EMS units stimulate the muscles and cause them to contract. Stimulating the muscles helps strengthen and tone as well as relax and rehabilitate them. If a person is looking to build muscle as part of a training program, an EMS unit is a good choice. However, for relief from acute or chronic pain, a TENS unit is the correct device to use.

To relieve pain and build muscle, there are some combination devices available with both TENS and EMS functionality. They are often more expensive than a standard TENS or EMS unit, but they can be a worthwhile investment if a person plans to benefit from both treatments. 

History of TENS therapy

TENS therapy is technically not a new method of pain relief. As far back as 2500 BC, people would use electric eels or fish to help manage pain. Even Hippocrates, the father of western medicine, treated the people of ancient Greece with this method.

As time went on, more discoveries were made that developed electrotherapy as a treatment method. In the 1600s, man-made electricity was discovered and studied. In 1747, Ben Franklin found that electricity could penetrate the body without damaging it. These discoveries paved the way for the development of dozens of first TENS machines in the 1800s. However, those devices (and electrotherapy as a whole) became largely irrelevant with the emergence of narcotic painkillers.

What caused TENS therapy to make a modern comeback? Here’s a brief overview:

  • 1964: Melzack and Wall’s gate control theory helps explain why electrotherapy relieves pain. This breakthrough causes electrotherapy to reemerge into modern medicine. 
  • 1974: American Neurosurgeon Clyde Norman Shealy patents the first version of today’s TENS unit. Following his invention, TENS therapy becomes more popular.
  • 1987: Ray Kriesler invents a TENS device specifically to be used during labor. This invention helps mothers who do not respond to traditional forms of labor pain relief, such as an epidural, and allows for a less painful natural birth. 
  • 1987–Present Day: Many studies are done to show that TENS units are effective treatments for a wide variety of acute and chronic ailments. Modern variations of Shealy’s original invention are created so anyone can find the best TENS unit for their specific needs. 

Why use a TENS unit? 

The following are benefits to using a TENS unit that set it apart from other at-home relief options:

  • Drug-free pain relief: TENS therapy is all-natural and drug-free, helping users manage pain without the risk of dependence or dangerous side effects. This makes it a safe alternative or supplement to prescription drugs and other treatment methods. See the “Are TENS units safe?” section for more information about safety and side effects.
  • Long-term solution: Because there are very few risks or side effects, users can manage pain with a TENS unit as frequently and as long-term as needed. 
  • Versatile: TENS units are effective in managing a wide variety of chronic and acute pain. See the “What are TENS units used for?” section for more information on its versatility. 
  • Controlled treatment: TENS units allow users to have more control over treatment than other options. There are multiple modes and intensity levels to choose from on a TENS device, and users can decide how long each treatment session will last based on need. 
  • Portable: TENS units are small enough to fit in a pocket or clip to a belt so that they can be used wherever. The subtle size and noninvasive electrodes also make it easy to use in public discreetly. 
  • Easy to use: TENS units may sound fancy and complicated, but they’re just as easy to use as an ice pack or heating pad. With a simple control panel and self-adhesive electrodes, users get the relief needed without hassle. 
  • Cost-effective: TENS units are one of the most affordable treatment methods available, with just a one-time purchase of $20 to $200 depending on its features and about $10 to $15 every few months to replace your electrodes. 
  • Over-the-counter (OTC) option available: TENS units are available by prescription and over the counter depending on type purchased. 

OTC vs. Prescription

While OTC TENS units are available and widely used, some TENS units require a prescription. The main differences between over-the-counter and prescription devices are their intensity levels and treatment modes. Typically, prescription TENS units offer higher intensity settings and more treatment modes, such as customizable frequencies and wave types. This allows them to target and relieve pain more precisely.

That said, prescription TENS units are often more expensive than OTC devices. Although OTC TENS units have lower intensity settings and only a few treatment modes to choose from, they are strong enough for most people.

What are TENS units used for?

Because TENS units offer customizable, targeted therapy, they can help treat a wide variety of pain. Below are some of the many ailments TENS therapy can help relieve. 

TENS units for back pain

TENS units are widely used to help treat upper and lower back pain. Still, unfortunately there is currently not enough evidence of the treatment’s effectiveness for the NHS to recommend it. One 2014 analysis found positive trends for chronic back pain while another study found that TENS therapy acted merely as a placebo. Either way, with thousands of users finding back pain relief using TENS therapy, it’s worth trying.  

One back ailment the NHS does recommend TENS therapy for is a herniated disc. Studies found it to be the most effective treatment option. 

TENS units for neck pain

The NHS recommends TENS units for neck pain. They can also be used to help treat neck pain related to cervical spondylosis. The neck is a sensitive area, though, and TENS therapy for neck pain should be conducted cautiously. It is recommended to place the electrodes right below the neck on the upper back. With this placement, electrical impulses can travel to the neck without irritating the neck’s sensitive area. 

TENS units for nerve pain

Because TENS units block nerves from sending pain signals to the brain, TENS therapy is an excellent option for nerve pain relief. This includes pain caused by nerve damage and pain associated with sciatica and complex regional pain syndrome (CRPS) when accompanied by other treatment forms. TENS therapy is also recommended by the Brain and Spine Foundation and the Foundation of Peripheral Neuropathy to help treat neuropathic pain

In addition to general nerve pain, some studies have found TENS units to be an effective treatment for vagus nerve pain.  

TENS units for knee pain

Studies have shown TENS therapy to help with various knee pain, including swelling, osteoarthritis, and post-surgery pain. Practitioners might also recommend TENS therapy to help treat meniscus tears and IT band pain, often accompanied by other treatment methods such as icing the affected area.

TENS units for migraines and headaches

Studies conducted in 2014 and 2018 both found that TENS therapy can help relieve pain from migraines. Additionally, both the U.S. Library of Medicine and the National Headache Foundation found that TENS units may help reduce headaches.  

TENS units for shoulder pain

Many users have found TENS therapy to be an effective method of helping to treat shoulder pain. TENS therapy has been recommended by the Oxford Shoulder and Elbow Clinic to help treat frozen shoulder. Many practitioners will also recommend it to help treat rotator cuff injury

TENS units for muscle pain

TENS therapy is very commonly used to help treat muscle pain. It is recommended by the NHS and has been found to effectively help treat sore muscles, muscle spasms, muscle knots, and muscle atrophy. TENS therapy also has a calming effect on the central nervous system, helping reduce pain related to fibromyalgia

TENS units for joint pain

TENS therapy has proven to effectively help treat joint pain, with reports showing successful pain relief and many users describing a positive experience. It’s also recommended to help treat arthritis by Arthritis Research UK and recommended to help treat bursitis by Cleveland Clinic

TENS units for face pain

While it is highly advised not to use a TENS unit on your face, TENS therapy can effectively help treat facial pain when conducted under proper supervision. A 2017 study found TENS therapy to be effective in helping treat Temporomandibular Joint Syndrome (TMJ). Additionally, a 2011 study found TENS therapy to be safe and effective in helping treat trigeminal neuralgia (TN). Treatment for either ailments must be done with medical supervision. 

TENS units for menstrual pain

Research shows that menstrual cramps and other period pain may be effectively helped using TENS therapy. Additionally, a study of 22 women found TENS therapy effective in helping treat pain related to endometriosis

TENS units for pregnancy and labor

TENS units have been found to be effective when helping treat pregnancy pain. However, the NHS does not recommend TENS therapy in the early stages of pregnancy. A TENS unit should never be used on the abdominal or pelvic regions while pregnant. Consult a doctor before using electrotherapy for pain relief. 

TENS therapy can help relieve pain during the early stages of labor, especially in the case of home birth. The NHS recommends it, and many moms believe it to be more effective than other early labor pain relief. 

TENS units for hip pain

Studies have shown that TENS units can be effective in helping relieve hip pain, including post-traumatic hip pain and hip flexor pain. Additionally, many users have highly recommended using TENS therapy for hip pain.  

TENS units for hand and wrist pain

Although more research needs to be conducted, a major TENS study found positive results when considering hand pain treatment. Additionally, a study conducted in 2010 found TENS therapy to help reduce pain related to Carpal Tunnel Syndrome significantly.

TENS units for elbow pain

While there is little conclusive evidence to show TENS therapy as an effective treatment method for elbow pain, users have reported positive results when using a TENS unit for Tennis Elbow. Some health clinics recommend it as a treatment for Golfer’s Elbow

TENS units for tinnitus

For some forms of tinnitus, TENS therapy can be an effective treatment method. For example, the U.S. National Library of Medicine found it to be successful in helping treat patients with ‘typewriter’ tinnitus. In contrast, another study found it to help those with tinnitus that worsened with neck movement.

TENS units for cancer pain

A study conducted by the Department of Anesthesiology has shown that some cancer pain can be reduced using a TENS unit. TENS therapy is also recommended to relieve cancer pain by highly regarded sources, such as Macmillan Cancer Support.

TENS units for stroke recovery

TENS therapy can also be useful in aiding in stroke recovery. One study found that using a TENS unit after experiencing a stroke can improve walking capacity and reduce spasticity. Another study found that electrotherapy can help improve movement and relieve shoulder pain post-stroke. 

TENS units for pelvic ailments

TENS therapy has been found to help reduce pain related to ailments in the pelvic area. For example, one study concluded that TENS can effectively help treat pelvic pain associated with pelvic floor dysfunction. The Interstitial Cystitis Association and The National Institute of Diabetes and Digestive and Kidney Diseases both recommend TENS for helping treat interstitial cystitis pain.

TENS units for abdominal pain

Research has shown that TENS therapy can effectively help reduce abdominal pain. A 2006 study showed TENS to help reduce pain during recovery from abdominal surgery. One study even found that TENS therapy can aid in digestion by increasing the salivary flow. 

TENS units for feet pain

TENS therapy can be incredibly useful in helping treat the feet with several TENS products specifically made to target foot pain available. The British Orthopedic Foot and Ankle Society recommends TENS therapy for heel pain in particular. Additionally, TENS therapy can help strengthen the foot muscle to help treat foot drop

Are TENS units safe?

Although sending electrical shocks to the body seems dangerous, TENS units are much safer than they sound. There have been no recorded instances of anyone being severely injured while using the device. The electric shocks delivered by the device are too weak to cause electrocution or other significant damage. The most users have to worry about is a harmless, surprising shock if they accidentally set the intensity up too high.

Side effects

Most people don’t experience side effects from using a TENS unit. However, the electrical stimulation may cause a tingling or buzzing sensation that can sometimes be uncomfortable. 

The electrodes can also sometimes irritate the skin and cause it to become red and itchy. This effect should go away shortly after removing the electrodes. However, if it persists, users may be allergic to the latex of the pads. Luckily, hypoallergenic, latex-free electrodes are an option. 

Because of the low risk, TENS units can be used as long and as often as needed. However, professionals recommend 30-minute sessions with 20-minute breaks in between. Overuse can sometimes cause soreness, a burning sensation on the skin, or uncomfortable muscle twitching.

Who shouldn’t use a TENS unit?

Although TENS units are generally low risk, users should always consult their doctor before using one to ensure that it is the right choice. In some instances, the device can be unsafe to use. It is recommended to not use a TENS unit if a user:

  • Is pregnant. Pregnant women should avoid using a TENS unit on the abdominal and pelvic regions.
  • Has epilepsy. Using a TENS unit on the head or neck can cause seizures. 
  • Has heart problems. 
  • Has a pacemaker or any electrical or metal implant. 
  • Has skin that is numb, irritated, or fragile. 
  • Is driving, using machinery, sleeping, or in the bath/shower. 

Always consult a doctor to make sure that a TENS unit is safe for use. 

Which TENS unit is best?

The number of available options can be overwhelming. In this section, we’ll go over what to consider (and what it all means) when selecting a TENS unit. 


Electrodes are the adhesive pads that administer the electric shocks to the body. They are usually reusable, and most TENS units will come with a pack to get started. Some electrodes have a higher quality stick than others. The most significant difference will lie in whether they are wired or wireless. 

  • Wired: Electrodes are most often connected to the unit using lead wires, with two pads per wire. These electrodes are more lightweight and can come with a range of wire lengths. Longer lead wires can be more comfortable and easier to use since they can reach farther. 
  • Wireless: Wireless electrodes can be more convenient since there aren’t any wires to get tugged on or in the way. However, these pads may be bulkier and heavier on the skin.

In addition to wired vs. wireless, it should be noted that many electrodes are made with latex. If you have a latex allergy, look for a TENS unit with hypoallergenic, latex-free pads


The number of channels refers to the number of lead wires that can be plugged in at a time. More lead wires means more electrodes, which allows users to target more, or larger, pain areas at a one time. Typically, there are three different channel types: single, dual, and quad. 

  • Single: One lead wire channel; two electrodes running at once.
  • Dual: Two lead wire channels; four electrodes running at once. 
  • Quad: Four lead wire channels; eight electrodes running at once. 

The average TENS unit will feature dual channels, which is typically the best for most users. 

Pulse duration

The pulse duration is the length of the pulse that the TENS unit administers. A longer duration means stronger stimulation. Most units will come with an adjustable range for maximum customization.

Pulse rate

The pulse rate is the rate at which the electric pulses are sent from the device, usually described in hertz or pulses per second. The pulse rate users choose will usually depend on the area of the body and the type of pain being treated. 2 Hz–10 Hz can help release endorphins to treat chronic pain, while 80 Hz–120 Hz can be best for acute pain. Like pulse duration, most units will come with an adjustable range for maximum customization. 


Most TENS units will come with a preset timer that automatically shuts off, so it doesn’t run continuously. Depending on the unit, the timer may not be adjustable. Users may need to restart the device for longer treatments. 

Intensity levels

Intensity levels determine how strong the treatment is. The higher the intensity level, the stronger the electrical current sent from the unit. Most TENS units go up to 80 mA while some go up to 100 mA. What users choose depends on the type and amount of pain, but most users don’t need more than 80 mA. Those with intensities higher than 80 mA are often prescription units. 


Most TENS units will come with a certain amount of modes, or “presets,” to choose from. These will have a predetermined pulse duration, pulse rate, timer, and intensity set for the treatment to make getting started easier. Some units might even allow users to choose different modes for different channels. Usually, the more expensive TENS units will feature more modes. 


Some TENS units are larger than others, making them less subtle and less ideal for on-the-go use. Consider how often the TENS unit will be used outside of the house. For regular outside use, users might prefer a smaller, more portable device. 


Some TENS units will come with a carrying case, extra electrodes, specialized equipment, and more. The amount of additional accessories the unit comes with will often add to the cost of the unit. 

TENS + EMS combo

Some units have both TENS and EMS capabilities. This is a great, convenient option for users who want to relieve pain and strengthen muscles, but it can add more to the cost. For pain relief only, a simple TENS unit will work. 

Battery type

Some TENS units use rechargeable lithium batteries while others use traditional, one-use batteries such as AAA or 9V. Rechargeable batteries can be a convenient option and save time and money in the long run. However, traditional ones also work just as well. 


Some brands have been making TENS units for years while others are relatively new. For reliability, it is recommended to choose a more established brand. 

How to use a TENS unit?

Using a TENS unit is relatively simple. Here’s a brief step-by-step:

  1. Connect lead wires to the electrodes.
  2. Connect lead wires to the TENS unit device.
  3. Clean the treatment area with soap and water.
  4. Place electrodes flat on the affected area. We will discuss proper electrodes placement below.
  5. Turn the machine on, keeping it at the lowest intensity level.
  6. If using a pre-set therapy mode, select the mode desired.
  7. If not using a mode or need to slightly adjust it, select the desired pulse width and rate.
  8. Set the timer if possible.
  9. If using the TENS unit for the first time, be sure to adjust the intensity, mode, and pulse width and rate until reaching optimal pain relief. 

How to place TENS unit electrodes

Proper placement of the electrodes is essential to receiving optimal pain relief. When targeting a specific area, place the electrodes on each side of the painful area. This placement allows the electrical current to pass through the targeted area. If using four electrodes, place each pad on each side of the targeted area in a square or diamond shape. 

There are some areas of the body that users should avoid placing the electrodes due to their sensitivity. These areas include:

  • On the throat or neck
  • Any part of your face or head
  • Over the eyes
  • In the mouth
  • On broken, numb, sore, or infected skin
  • Over a joint such as a knee, elbow, or ankle
  • Over or around the heart

Points to remember when using a TENS unit

  • Do not use the TENS unit while sleeping, driving, swimming, or in the bath/shower. 
  • Muscles may twitch when using the TENS unit at high-intensity levels.
  • The intensity felt may be increased if sitting back in a chair with electrodes on the back, as it increases the pads’ contact with the skin.
  • If irritation occurs and persists, cease treatment, and consult a doctor.
  • Users may not immediately feel pain relief when the treatment begins. It’s best to start at a lower intensity and continue to increase and change modes as needed.
  • TENS units are not a cure for any physical ailment. They are a tool for pain relief. It is best to continue any therapy or other treatment already in place while using TENS therapy. 

How to maintain a TENS unit


TENS units are designed for repeated use over time without very much maintenance. Still, users should always make sure the unit is not damaged and is working correctly before use. This includes checking the device itself, the electrode cords, and the batteries for leakage. Never try to use a damaged unit.

To clean a TENS unit, turn it off and disconnect and cords beforehand. Use a damp cloth (no chemicals, only water or a neutral cleaning solution) and wipe the surface gently, careful not to get water inside the device. 

Store the unit in an area that is away from direct sunlight, humidity, or high voltage. If storing for an extended period, remove the device’s batteries to prevent leakage. 


Most electrodes are reusable and can last up to 5 to 6 months. That said, there are some things users can do to help electrodes maintain their stickiness and last as long as possible:

  • Clean skin with soap and water before each use. The skin’s natural oils can dirty the electrode and make it less sticky. 
  • Clean electrode pads with a moist towel or washcloth after each use. This helps remove dirt or oil and bring back some stickiness. 
  • Use a conductive gel or spray with each use to help preserve or regain the moisture of the pad.
  • Store the pads in their packaging, so they don’t dry out. 

It’s best to replace electrodes once they no longer stick to skin, or a majority of the pad is not in contact with the skin. 

Are TENS units covered by Medicare?

TENS units prescribed by a physician can be covered by Medicare, but only under some circumstances. Suppose a user is using a TENS unit to help treat acute postoperative pain. In that case, Medicare Parts B and C will cover the cost of renting the device for up to 30 days (sometimes more if exceptionally necessary). 

Medicare Parts B and C will also cover a TENS unit used to help treat chronic pain lasting more than 3 months as long as no other standard pain relief methods have proven effective. Initially, Medicare will cover the cost of renting the device for 30 to 60 days. If a physician certifies that the device will likely provide the user with long-term pain relief, Medicare may cover the cost of purchase. 

Unfortunately, this does not include TENS units for chronic back pain, headaches, internal abdominal pain, TMJ pain in the jaw or face, or other pain types that do not typically respond to TENS treatment. 

Are TENS units FSA eligible?

Yes, OTC TENS units are eligible for purchase or reimbursement with a flexible spending account (FSA), health savings account (HSA), or health reimbursement arrangement (HRA)! Unfortunately, they are not eligible for reimbursement with a limited care flexible spending account (LCFSA) or a dependent care flexible spending account (DCFSA).

This content was originally posted by Richmar at and is used with permission.

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