TENS unit safety: who should not use one, where pads must not go, and when to stop

Is a TENS unit safe?

For many people, a TENS unit is safe when used as directed. It is not safe for everyone, and some uses are off limits. Check with a clinician before you start.

The NHS says: “If you want to try TENS for pain relief, it’s a good idea to check with a GP or other healthcare professional first, to make sure TENS is safe for you.” The NHS is the UK national health service. Its page was last reviewed in February 2025.

University of Iowa Health Care (page reviewed January 2019) asks, “Can TENS harm my body?” Its answer: “No, but it can cause some skin irritation from the patches.” It also says a TENS unit should not hurt: “Make sure you are setting it at a strong but comfortable intensity.”

An electrical device can still cause problems. The same page says you can get shocked if you move or remove pads or wires without turning the unit off, if the unit gets wet, or if you touch bare wires on a damaged cord.

This guide pulls together the two sources. Use it with your clinician’s and your device’s instructions, which always come first. Our TENS units overview explains the basics.

Who should not use a TENS unit?

Some people should not use TENS at all, and some should ask first. The two sources do not match exactly. Follow the stricter rule.

A contraindication is a reason not to use a treatment. Each row above is one. If any row fits you, ask your clinician before you use a unit.

Do not let anyone else use your unit or pads. University of Iowa Health Care says: “Just as you would not let others take a medicine that was only prescribed for you, you should not let others use your TENS unit.”

For a printable list, see our TENS safety checklist.

Can I use a TENS unit with a pacemaker or other implanted device?

No. Both sources say do not use TENS with a pacemaker.

The NHS lists “you have a pacemaker” under “Do not use TENS if.” University of Iowa Health Care is broader. It says: “Do not use TENS if you have: A cardiac pacemaker or defibrillator Spinal cord stimulator In-dwelling pumps or monitors Any implanted metallic or electronic device.”

A cardiac pacemaker is a small device that helps control your heartbeat. An implanted medical device is any device placed inside your body, such as a pacemaker, a defibrillator, or a spinal cord stimulator.

University of Iowa Health Care also says that “Electronic equipment, such as EKG monitors and EKG alarms, may not work the right way when TENS is in use.” Tell any clinician who monitors you that you use TENS.

If you have an implanted device, do not try TENS on your own. Ask the clinician who manages your device. Our post on TENS units and pacemakers covers the question in more detail.

Can I use a TENS unit if I am pregnant?

Ask your doctor or midwife first, and do not start without their advice. The NHS says not to use TENS if “you’re pregnant, unless your doctor or midwife tells you to.”

University of Iowa Health Care takes a similar view. It lists pregnancy under “Talk with your health care provider if you have.”

The NHS page lists labour pain in pregnancy as one use of TENS, so ask your doctor or midwife about your own case. If you are pregnant or could be, tell your clinician before you start.

Where on the body should TENS pads never go?

Never place pads on the head, face, throat, neck, mouth, or eyes, or on damaged or numb skin. Both sources give lists.

University of Iowa Health Care says: “Do not use TENS on: Open wounds or rashes. Swollen, red, infected, or inflamed skin. Cancerous lesions, or close to them. Skin that does not have normal sensation (feeling). Any part of your head or face. Any part of your throat. Both sides of the chest or trunk at the same time. Directly on your backbone.”

The NHS says: “Do not use TENS on irritated, broken, infected or numb areas of skin. Do not use TENS on your neck, mouth or eyes. Do not use TENS on your chest and back at the same time.”

The patches also should not touch each other or any metal object, such as a belt buckle or metal jewelry, says University of Iowa Health Care. It advises placing pads on fleshy areas, not boney sites.

Our post on where not to put TENS pads goes deeper. For where pads can go, ask your clinician. The NHS says a clinician such as a physiotherapist can advise if you are unsure.

When should I never use TENS?

Do not use TENS while you sleep, bathe, shower, or drive. These rules appear in both sources.

The NHS lists: “Do not use TENS while you sleep. Do not use TENS in the bath or shower. Do not use TENS when driving or using tools or machinery.” University of Iowa Health Care lists the same activities: “Bathing or showering, Sleeping, Driving, Using machinery.”

The reasons from University of Iowa Health Care are plain:

• Sleeping: “It is easy for the wires to get tangled or unplugged, or the patches may come off.” Not wearing it to bed “also lets your skin rest.”
• Shower or bath: “There is a chance for electrical shock since it is an electrical device. Also, the unit is not waterproof and would be damaged.”

That page also says TENS is most helpful during activities such as walking, doing chores, or exercise. Plan your TENS time for activities that are safe for you, and follow your clinician’s advice. Our post on using TENS while sleeping covers that rule.

Other protection rules from University of Iowa Health Care:

1. Turn the unit off before you put on, move, or take off the electrode pads.
2. Do not share your pads with other people.
3. Use the unit only on yourself, as instructed.
4. Keep the unit out of the reach of children.

What side effects mean I should stop?

Stop using TENS and call your clinician if you have skin irritation, headache, dizziness, or nausea. This is the University of Iowa Health Care list, word for word: “Stop using TENS and talk with your doctor or health care team if you have: Skin irritation (redness, rash, itching) Headache Dizziness Nausea (feel like you are going to throw up).”

The NHS adds a skin rule: “If your skin becomes itchy, irritated or red (redness may be harder to see on brown or black skin), turn off the machine and remove the pads.”

Also stop if the unit hurts. The NHS says the tingle “should not be painful.” If you feel pain, turn the unit off and call your clinician.

If you feel seriously unwell at any time, get emergency help. Tell your clinician what happened before you use the unit again.

Do not change or stop a medicine because of TENS. Ask your clinician.

How do I protect my skin?

Use clean, dry skin and check it after each session. Skin irritation is the main reported problem.

University of Iowa Health Care gives these tips:

• Make sure the skin is “clean (clean off oil/lotion) and dry” so the pads make firm contact.
• Wash pads gently with your fingertips under slow-running cold water if they are dirty, then air-dry them.
• Put pads back on their plastic liner and in the storage bag after use. They stay sticky longer.
• If pads slide because of sweat, a skin prep product may help. Ask your clinician about medical tape.
• If redness, a rash, or itching appears in the first 24 hours, call your health care team and move the pads to a different site.
• Do not put pads on broken or irritated skin.

People allergic to nickel or adhesives “may have skin irritation with TENS,” says that page. The NHS says a healthcare professional “can also tell you about alternatives if your skin is sensitive to the sticky pads.”

Check your skin after you remove the pads. Look for redness, rash, or blisters. Report anything unusual.

Is it safe to use a TENS unit every day?

Follow your clinician’s and your device’s instructions. No single safe schedule fits everyone.

University of Iowa Health Care answers the question: “Do I have to use my TENS unit daily? Can I take a break?” It says: “You can take a break; 3 to 5 days off may be helpful. If your pain is at a manageable level, you may want to leave the unit off and wait to use it again when you have a flare-up. Some people use their TENS only when their pain is most severe, while others use it daily.”

The same page gives a caution about long sessions. It says “Having your muscles twitch for longer than 30 minutes may cause them to get tired or sore.” It also says the stimulation may feel weaker after a few minutes, and that you can turn up the intensity so it stays “strong but comfortable.”

So the safe approach is steady and simple:

1. Start with the settings your clinician gave you.
2. Check your skin before and after each use.
3. Take rest days if your clinician says to.
4. Call your clinician if your skin, your sleep, or your pain pattern changes.

Who do I call with questions?

Call your own clinician first. They know your health history, and they can tell you if TENS is safe for you.

The NHS says to read the leaflet that comes with your machine for the full list of things you should not use TENS for, and to “check with a healthcare professional if you’re not sure.”

For questions about getting a TENS unit, you can reach Analgesic Healthcare, Inc. (AHC) at (800) 749-1188 or through the contact page. AHC is based at 7823 N. Dale Mabry Highway in Tampa, Florida. This page is general information. It does not replace advice from your clinician.

Next step

Talk with your clinician about whether TENS is safe for you, and bring this list. Then call Analgesic Healthcare at (800) 749-1188 or use our contact page with questions.

This page gives general information, not medical advice. Talk with your doctor or physical therapist about your own care, and follow your clinician's and your device's instructions. In an emergency, call 911.