By Mike Shilling, Recovery & Training Editor · Updated 6 November 2026
A TENS machine can make pain worse, but when it does, the cause is almost always how it's being used rather than the device itself. Crank the intensity past a comfortable tingle, stick the pads over the wrong area or on irritated skin, or leave it running for hours, and you can end up sorer than when you started. Used properly, TENS is low risk and gives some people temporary relief. It doesn't work for everyone, and it isn't a fix for the underlying problem.
TENS (transcutaneous electrical nerve stimulation) sends a weak current through sticky pads on your skin. The NHS page on TENS says it's thought to work by encouraging your body to release endorphins and by stopping pain messages reaching the brain. Each of the problems below has a fairly obvious fix once you know what's going on.
The NHS instruction is to turn the dial slowly until you feel a tingling sensation, and that "it should not be painful". Plenty of people assume more is better and push it until it bites. A strong but comfortable buzz is the target; a 2022 review of the TENS evidence in Medicina found that stimulation intensity is critical to whether TENS works at all, so going too low is also a waste of time. Too high, and you're adding a second source of discomfort on top of the first.
At higher settings, or on programmes designed to make muscles contract (many cheap units double as EMS muscle stimulators), the current can make muscles twitch or tighten. Repeated contractions over an already sore back or calf can leave it aching the next day. If you see visible twitching and you're using the unit for pain, turn it down or switch to a pain programme.
This is the side effect that turns up most in the research. The 2008 Cochrane review of TENS for chronic low back pain reported minor skin irritation under the electrodes, seen about equally in people using real and placebo TENS, plus one person who developed a severe rash four days in. That points at the adhesive and gel rather than the current. Old, dried-out pads also concentrate the current into a smaller patch of skin, which stings. Replace pads when they stop sticking properly, and stop if your skin goes itchy, red or sore.
Pads over a bony area, too close together, or nowhere near the painful spot either do nothing or produce a sharp, uncomfortable sensation. The NHS advice is to place them on clean skin near the painful area with a gap between them.
Running a unit all day can irritate the skin and, for some people, the area just feels more sensitive afterwards. Shorter sessions with breaks are better than one marathon.
This is the one to take seriously. TENS reduces how much pain you feel; it doesn't treat the cause. If you're numbing a fresh injury so you can keep training on it, the pain may well be worse next week. The NHS says that if you're not sure what's causing your pain, you should see a healthcare professional before using a TENS machine.
When to stop and get checked
Stop using TENS and speak to a GP or physio if your pain keeps getting worse over a few days, if you have numbness or weakness in a leg, or if the pain followed a fall or accident. Loss of bladder or bowel control, or numbness around the groin or buttocks, with back pain needs urgent medical help (call 999 or go to A&E), not a TENS machine.
The steps below follow the NHS instructions, plus a few practical additions. Your device leaflet has the final say for your model.
If you can't work out where the pads should go, a GP, physio or midwife can show you, and they can suggest options if the pads irritate your skin.
There's no universal maximum, which is why the leaflet matters. In the 15 trials pulled together by the 2017 Cochrane review of TENS for neuropathic pain, session times ranged from 15 minutes up to hourly sessions four times a day, over anywhere from four days to three months. Most people do fine with sessions of 20 to 60 minutes, a break of a similar length between them, and a few sessions a day at most.
You can use TENS daily if your skin tolerates it. The two hard rules from the NHS are that you shouldn't use it while you sleep, and you shouldn't use it in the bath or shower.
The NHS is specific here. Do not use TENS if:
The NHS page doesn't list heart conditions in general, only pacemakers. Many device leaflets go further and exclude people with other implanted electrical devices (such as an implanted defibrillator, or a spinal cord or nerve stimulator) and people with heart problems, so if any of that applies to you, check with your GP or cardiology team before buying one. The NHS also recommends checking with a GP or other healthcare professional before trying TENS at all, to make sure it's safe for you.
Pregnancy needs one clarification. Labour TENS units are a separate, well-established use, but that's labour, under midwife guidance. It doesn't mean general use for back pain at 20 weeks is fine.
The NHS also says not to use TENS:
Honest answer: it might help a little, short term, for some people, and the evidence is weak. Sciatica is nerve pain (usually from an irritated nerve root in the lower back), so the best match in the research is the 2017 Cochrane review of TENS for neuropathic pain, which included back pain with nerve involvement. Its authors couldn't say with any confidence whether TENS relieves pain better than a sham device, because the quality of the evidence was very low.
For plain back pain, the older Cochrane review on chronic low back pain found conflicting evidence on pain and consistent evidence from two trials (410 patients) that TENS didn't improve back-related disability. NICE guideline NG59 on low back pain and sciatica is blunt: "Do not offer" TENS for low back pain with or without sciatica.
So if you already own a unit and it takes the edge off while you walk or do your exercises, there's little harm in using it sensibly. Just don't expect it to be the treatment. Movement does more for most sciatica, and our sciatica exercises and lower back stretches guides are a better place to put your effort. If leg pain lasts more than a few weeks, or you have numbness or weakness, see a GP or physio.
Look for a CE or UKCA mark, which the NHS says means the machine meets the right standards. Simple units with dedicated pain programmes are easier to get right than 70-programme TENS/EMS combos, where it's easy to land on a muscle-contraction mode by accident. The OMRON PocketTENS is a small, basic option with three preset pain programmes (arm and shoulder, lower back, leg and foot), two massage-style modes and 10 intensity levels. It's around £22 at the time of writing. We haven't tested it ourselves; this is based on Omron's listed features.
TENS isn't the only drug-free option for sore muscles. A massage gun or a foam roller works on muscle tightness rather than pain signals, and some people pair them with red light therapy for recovery, though that evidence is mixed too.
It can, though it isn't common. The usual causes are an intensity set too high, pads placed in the wrong spot, skin irritation from the pads or gel, and sessions run for hours on end. Muscle twitching at high settings can also leave muscles sore. If your pain keeps getting worse after a few sessions, stop and see a GP or physio, because TENS may be masking a problem that needs diagnosing.
Some people find it takes the edge off, but the research is weak. A 2017 Cochrane review of TENS for nerve pain, which included back pain with nerve involvement, couldn't say with any confidence whether TENS beats a sham device, and NICE guidance (NG59) tells clinicians not to offer TENS for low back pain with or without sciatica. Treat it as a short-term comfort tool at best, alongside exercise and proper assessment.
There's no single official limit, so follow the leaflet for your device. Trials have used anything from 15 minute sessions to hourly sessions four times a day. A sensible starting point is 20 to 30 minutes, then switch off, let the skin rest and check it for redness before the next session. Don't use it while you sleep.
Yes, most people can use TENS daily if their skin tolerates the pads and they aren't in one of the groups who shouldn't use it. Move the pads slightly between sessions, keep the skin clean and dry, and stop if you get itching, redness or a rash.
The NHS says not to use TENS on your neck, mouth or eyes, on irritated, broken, infected or numb skin, or on your chest and back at the same time. Keep pads off the front of the throat and never place them across the head.
Only if your doctor or midwife tells you to. The NHS lists pregnancy as a reason not to use TENS unless you've had that advice. Labour TENS units exist and many midwives are happy for women to use them in labour, but that's a specific use under guidance, not general pain relief during pregnancy.
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