TENS Unit for Period Cramps and Endometriosis: Does It Help?

A TENS unit can ease period cramps for some people. In small trials, TENS relieved period pain better than a fake (sham) TENS, but the proof is limited, and for endometriosis pain it is thinner still.

TENS is drug-free and well tolerated in the trials, so it can be worth a try next to your usual painkillers. This guide covers what the trials show, where to put the pads, which settings were tested, who should not use TENS, and when pain needs a doctor.

For all the main ways to ease cramps side by side, see our guide to what helps period cramps. This page is only about TENS.

Quick answer

What a TENS machine is

TENS stands for transcutaneous electrical nerve stimulation. A small machine sends a weak electrical current through sticky pads on your skin. You feel it as a tingle. It gives temporary pain relief, and period pain is one of the conditions it can help.

For severe period pain, a GP may recommend a TENS machine. You can also buy one online or from a pharmacy. It is best to check with a GP or pharmacist first that TENS is safe for you.

Does TENS help period cramps?

The trials are small, but they point the same way:

• A review of 7 randomised trials with 164 women found that high-frequency TENS relieved period pain better than placebo TENS. Low-frequency TENS was no better than placebo.
• A later analysis of 4 trials with 260 women found that TENS reduced period pain more than sham TENS. It called TENS safe and well tolerated.

How strong is this evidence? Low. The trials were small, and many were not blinded, which matters for a treatment you can feel. The Cochrane review concluded that clear recommendations for practice cannot be made. So TENS is a reasonable thing to try, not a sure fix.

Does TENS help endometriosis pain?

There is much less research. The largest trial put 101 women with deep endometriosis who still had pain on hormone treatment into two groups. One group added self-applied TENS for 8 weeks, and the other kept hormone treatment only. Pelvic pain fell from about 7.1 to 4.6 out of 10 in the TENS group only. Pain during sex eased in both groups, and more in the TENS group.

That result is hopeful but limited. There was no sham TENS group, so the women knew which treatment they had. The trial lasted only 8 weeks, and it came from one research team.

The 2022 ESHRE endometriosis guideline found that no recommendation can be made for electrotherapy, or for other non-medical treatments, because the benefits and harms are unclear. It still asks doctors to talk with you about non-medical ways to cope.

If you have endometriosis, TENS is an extra option next to medical treatment, not a replacement. For other ways to get through a bad day, see our guide to an endometriosis flare-up.

Where to put TENS pads for period cramps

Put the pads on clean skin near the painful part of your body, with a gap between them. In the period pain trials, the pads went on the lower belly, the lower back, or both.

Do not put the pads on your neck, mouth or eyes, or on your chest and back at the same time. Follow the leaflet that comes with your machine.

Which settings to use

• Strength: turn the dial up slowly until you feel a tingle that is not painful.
• Frequency: the setting that worked better than placebo was high-frequency TENS, about 50 to 120 Hz, at a low, comfortable strength. Low-frequency TENS, 1 to 4 Hz, did not beat placebo.
• When: most trials used TENS during the period, when the pain was there.
• How long: check your machine's leaflet.

Who should not use TENS

Do not use TENS if you have epilepsy or a pacemaker. If you are pregnant, do not use it unless a doctor or midwife tells you to. If you have another implanted device or a heart condition, or you are not sure what causes your pain, see a healthcare professional before you use TENS.

Also do not use TENS:

• On skin that is irritated, broken, infected or numb
• While you sleep, in the bath or shower, or while you drive or use tools or machines

If your skin gets itchy, irritated or red, turn the machine off and take the pads off. In one trial, a few women had muscle tightness, headaches, or red or burning skin with high-frequency TENS.

TENS and painkillers

TENS does not replace painkillers. For period pain, paracetamol or ibuprofen are the usual first step. In the one trial that compared them, ibuprofen relieved pain better than high-frequency TENS. In another, there was no clear difference between TENS and naproxen.

You can use TENS next to the usual treatment, as the endometriosis trial did with hormone treatment. Because it is drug-free, it can also help on days when you cannot take NSAIDs. To choose between the two common NSAIDs, see ibuprofen vs naproxen for period cramps.

What to track

If you try TENS, a short record shows if it helps you. For each session, note:

• Your pain score before and about an hour after
• Where the pain was and where you put the pads
• The setting you used
• Any painkillers you took, and when
• The day of your period

Endolog is a pain and symptom diary for endometriosis and adenomyosis. You log pain severity and where it hurts, bleeding and other symptoms with notes, and you can share a PDF report with your doctor. A paper notebook works too.

When to see a doctor

See a GP or doctor if any of these are true:

• Your periods become more painful, heavier or irregular
• Period pain stops you doing your usual daily activities
• You bleed between periods

Ask for an urgent appointment, or call NHS 111 in the UK, if your pelvic or period pain is severe or worse than usual, and painkillers have not helped.

Pain that TENS and painkillers do not control is a reason to ask about endometriosis or adenomyosis. You do not have to put up with it.