TENS unit settings explained: intensity, frequency and pulse width

What do the settings on a TENS unit control?

Most TENS units let you change three things: how strong the pulses feel, how often they come, and how long each pulse lasts. A TENS unit sends mild electrical pulses through electrode pads on your skin to relieve pain.

Your device may use other names or fewer controls. Some units have preset programs. Read your manual to see which controls yours has.

This guide explains what the settings mean. It does not give you a personal setting. Follow your clinician’s and your device’s instructions. Read the TENS unit safety guide before you start.

How strong should the intensity be?

Set intensity to strong but comfortable. It should not hurt. University of Iowa Health Care (UI Health Care) says: “Start treatment and change the intensity to be strong but comfortable.”

The NHS gives the same direction in other words. It says to turn the dial slowly until you feel a tingling sensation, and that “It should not be painful.”

Intensity matters. A 2022 review in the journal Medicina, “Using TENS for Pain Control: Update on the State of the Evidence,” says “stimulation intensity has been documented as critical to therapeutic success.” UI Health Care adds that turning the unit up so that you barely feel it will not give pain relief, according to research it cites.

Here is how to read the feeling:

Why does the feeling fade, and what should I do?

The feeling can fade after a few minutes because your body gets used to it. UI Health Care says this is normal. It says to turn up the intensity to keep it “strong but comfortable.”

Do not jump to a high number. Raise the dial a little at a time. If the unit feels strong enough to hurt, lower it.

What are frequency and pulse width?

Frequency is how many pulses come each second. Pulse width is how long each pulse lasts. The 2022 review says, “The parameters of pulse frequency and pulse intensity are adjustable and linked to TENS efficacy.”

The review also describes how researchers label frequency: “TENS can be applied with low frequencies (LF), <10 Hz, high frequencies (HF), >100 Hz, or mixed frequencies (LF and HF).” Those are research labels, not a setting for you. They show that low, high and mixed frequencies all exist.

Some details to keep in mind:

• The review reports the settings used in single studies. Those values are not instructions for patients.
• The review says systematic reviews commonly describe “limited reporting on TENS parameters.” That means the right values are still unclear in the research.
• Ask your clinician which pulse width suits you, and use the setting on your own device.

Ask your doctor or physical therapist which frequency and pulse width fit your pain. Follow your clinician’s and your device’s instructions.

How long should one session last?

Your clinician or your device sets the plan. One source gives a time. UI Health Care says: “Research has shown that TENS is most helpful for chronic pain when used for at least 30 minutes while you are active.” It adds that TENS is less effective when you are sitting still, lying down or resting.

UI Health Care also says you can take a break. It says 3 to 5 days off may be helpful. If your pain is at a manageable level, you may wait until a flare-up. Some people use TENS only when pain is most severe, and others use it daily.

Do not wear a TENS unit while you sleep, bathe, shower or drive. The NHS and UI Health Care both say so.

What do the modes on my device mean?

Mode names differ by brand. Your manual lists your modes. Your clinician can tell you which one to use.

If your device also lists words like EMS or NMES, those are different kinds of stimulation from TENS. Read the TENS vs EMS, NMES and interferential guide before you try them.

What are common mistakes with TENS settings?

Most mistakes come from rushing or guessing. Avoid these:

1. Setting intensity too low. UI Health Care says barely feeling it will not give relief.
2. Setting intensity so high that it hurts. Both sources say it should not hurt.
3. Changing pads with the unit on. UI Health Care says you can get shocked if you reposition or take off pads without turning the unit off first.
4. Using a wet unit. UI Health Care says you can get shocked if the unit gets wet.
5. Ignoring your plan. UI Health Care says to follow the treatment program in your After Visit Summary.
6. Skipping the clean skin step. A loose pad can change the stimulation.
7. Trying a new mode without asking. Mode names differ by brand, and your clinician chose your plan for your pain. Ask before you change it.
8. Sharing your unit. UI Health Care says not to let others use your TENS unit, just as you would not let others take a medicine prescribed for you.

If you do not get relief, UI Health Care suggests these steps in order: do not use the unit for 3 to 5 days, then try again; try a different setting; turn up the intensity to strong but comfortable; try changing the pad position. Call your health care team if you still cannot get relief.

What should I write down for my doctor?

Keep a short log. It helps your clinician adjust your plan. Medicare’s policy article for TENS (A52520) lists what a clinician records at the end of a trial: the length of time you have had the pain, how often you used the unit, the typical duration each time, and the results. A log of the same things makes your visit faster.

Bring the log to your next visit. The TENS trial period guide shows how a clinician uses this kind of record.

What is a safe order of steps when I change a setting?

Turn the unit off before you touch anything else. UI Health Care says to turn the TENS unit off before you put on, move or take off the pads. The NHS says to start with the machine off and then use the controls to set the current.

A simple order works for most people:

1. Turn the unit off.
2. Place or move the pads.
3. Turn the unit on at the lowest level.
4. Raise intensity slowly until it feels strong but comfortable.
5. Turn the unit off before you remove the pads.

This order protects your skin and lowers the chance of a shock. The pad placement guide covers where the pads go.

Who should not change settings without help?

Anyone with a health condition that affects TENS use should ask a clinician first. The NHS says not to use TENS if you have epilepsy or a pacemaker. UI Health Care says not to use it with a cardiac pacemaker, defibrillator, spinal cord stimulator or any implanted metallic or electronic device. It says to talk with your health care provider if you have cancer, diabetes, cognitive impairment or epilepsy, or are pregnant.

A contraindication is a reason not to use a treatment. Check the TENS unit safety guide for the full list. Never raise settings to “push through” pain. Stop and call your clinician instead.

Does my plan or Medicare look at my settings?

Medicare’s policy asks a clinician to watch how the unit works during a trial. LCD L33802 says: “The trial period must be monitored by the treating practitioner to determine the effectiveness of the TENS unit in modulating the pain.” Your settings and your log help the clinician do that. Read the Medicare TENS coverage guide for the rules. Private plans have their own rules, so check with your plan.

Next step

Ask your doctor or physical therapist to write down your settings and your plan, then follow it. If you have questions about getting a TENS unit, call Analgesic Healthcare at (800) 749-1188 or use the contact page.

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.