Does keeping your phone in your pocket lower your sperm count?

The pocket twist

I keep seeing this claim: the phone in your front pocket is quietly damaging your sperm. Plenty of men worry about it without saying so, so it’s worth checking what the research found.

The biggest study on the question comes from Switzerland. Scientists looked at almost 2,900 young men and compared their phone habits with their semen samples. The result surprised me. Where the men kept their phone didn’t seem to matter. How often they used it did, and even that link faded as phones and networks got newer.

There’s a catch, and I’ll get to it. But first: what’s actually sitting in your pocket?

The claim, and why it’s a fair worry

I’m not a scientist. I read the studies behind the scary posts. First it was 5G, then AirPods. This one is closer to home.

The claim usually goes like this: your phone is a radiation source pressed against your body all day, right next to your reproductive organs, and over time it’s wearing down your fertility.

Honestly, it’s a reasonable worry. Your phone is the strongest radio transmitter you own, and in a trouser pocket it’s touching you for hours. So let’s start from the ground up.

What a phone actually is

Physically, a phone contains three kinds of thing that make fields.

• Radios. The cellular radio is the strong one. A 4G or 5G phone is designed to transmit at up to about 200 milliwatts (ETSI). Old 2G phones could reach 2 watts at peak (ETSI TS 145 005), though only in short bursts. Wi-Fi, Bluetooth and the smaller radios are much weaker.
• The battery and circuits. Current flowing through them makes weak, low-frequency magnetic fields. A survey of 47 GSM phones from 1997 to 2008 measured a typical maximum of about 0.2 microtesla at 2.5 cm (Calderón et al. 2014).
• Magnets. There are static magnets in the speaker, and in the ring that holds MagSafe accessories.

Remember those magnets. They come back at the end.

Non-ionising: the ladder, briefly

All of these fields are non-ionising. If you’ve read the 5G article, you’ll know the ladder: radio waves sit at the bottom of the spectrum, far below the line where each photon carries enough energy to break DNA. X-rays sit above that line. Phones don’t.

So the question isn’t whether your phone can damage your genes the way an X-ray can. It can’t. The only proven effect of radio waves on tissue is heating. The real question is whether a phone can warm tissue enough to matter, or do something subtler.

Why centimetres matter

Distance matters. Close to an antenna, in what engineers call the near field, exposure is at its strongest, and it drops off steeply over the first few centimetres.

That’s why a tower a hundred metres away and a phone touching your leg are completely different situations, and why the pocket question is worth asking even after the 5G one.

The phone mostly whispers

Here’s something most people don’t know: your phone mostly transmits far below its maximum. The network constantly tells it how loud to transmit, and when the signal is good, it turns itself right down. Engineers call this adaptive transmit power.

France’s radio regulator, ANFR, has put a number on it. On a 4G call with excellent reception, the energy your body absorbs averages about 8,000 times below the maximum measured in the lab (ANFR). That’s a figure for absorbed energy, not raw transmitter power. ANFR also notes that on a call a phone transmits only about half the time, and in a data session rarely more than 10% of the time.

The phone mostly whispers

How hard a phone really transmits, compared with its lab maximum

Lab maximumworst case, full power

100%

2G calls: average power60,000+ calls, 12 countries

≈ 50%

4G call, excellent receptionabsorbed energy, average

≈ 8,000× lower

0%50%100%

Other networks tell the same story. A field study on a 3G network found that average output on voice calls was under 1% of maximum (Persson et al. 2012). Old 2G was far louder: across more than 60,000 calls in 12 countries, phones averaged about half their maximum power and ran at full power 39% of the time (Vrijheid et al. 2009).

The flip side is that a phone shouts when the signal is weak: in a lift, a basement, on a train, out in the countryside. Hold on to the 2G-versus-4G difference, too. It matters for the Swiss study.

How a pocket is tested: SAR at zero millimetres

Regulators check phones using SAR, the specific absorption rate: how much radio energy a kilogram of tissue absorbs, measured in watts per kilogram. Under the ICNIRP 2020 guidelines and Australia’s ARPANSA standard, the limit is 2 W/kg for the head and torso and 4 W/kg for the arms and legs, averaged over 10 grams of tissue.

Those limits are set ten times below the level where heating could start to do harm (BERENIS 2020).

In France, a phone in a trouser pocket is tested as a limb. It’s pressed directly against a model body, at 0 mm, at full power, averaged over six minutes, against the 4 W/kg limit. That’s the worst case. ANFR has been able to test phones this way since July 2020 and published its first limb results that December (ANFR). A jacket pocket or a bag counts as torso, with the 2 W/kg limit.

There’s one honest wrinkle. Until April 2016, EU torso tests could be done at any distance up to 25 mm, chosen by the manufacturer. Since then the maximum has been 5 mm (ANFR 2025 report, Annex 1). So some older phones sat closer to your body in a pocket than they did in their own test.

When phones failed the test

Sometimes phones fail. The best known is the iPhone 12 in France. In 2023 ANFR measured its limb SAR at 5.74 W/kg against the 4 W/kg limit, and on 12 September it ordered a provisional withdrawal from sale. A modem update shipped with iOS 17.1 brought the reading down to 3.94 W/kg, and the ban for mainland France was lifted on 26 October, about six weeks later (ANFR).

ANFR’s 2025 campaign tested 80 devices from 33 brands (ANFR 2025 report). Limb SAR ranged from 0.35 to 6.25 W/kg, with a median of 2.31. Eight devices went over the limb limit and one over the head limit, mostly from lesser-known brands:

• Fixed by software update: Blackview Shark 8, Nokia 110, Crosscall Core S5 and Oukitel WP36.
• Withdrawn: Ulefone Note 16 Pro, Oukitel WP28, Doogee X98, Fossibot F105 and Hotwav Note 13.
• No Apple or Samsung phone failed.

The study

REGULATOR

ANFR’s 2025 SAR campaign

WHO

ANFR, France’s radio regulator

DESIGN

Lab SAR tests; pocket tested as a limb at 0 mm

YEAR

2025 campaign, report May 2026

n

80 devices from 33 brands

RESULT

9 over a limit; 4 fixed, 5 withdrawn

It sounds alarming. But these are breaches inside a tenfold safety margin, in a worst-case test at full power, and ANFR itself framed the iPhone case as a compliance issue, not a health danger.

The case for worry: sperm in a dish

Now the fertility worry itself, which deserves a fair hearing. It started in the lab, with real experiments by serious scientists.

In 2009 a team at the Cleveland Clinic, including Ashok Agarwal, put 32 semen samples next to a phone in talk mode for an hour (Agarwal et al. 2009). The exposed sperm swam less well, fewer were viable, and there were more signs of oxidative stress, a kind of chemical wear on cells. They found no significant DNA damage.

The same year in Australia, Geoffry De Iuliis, John Aitken and colleagues at the University of Newcastle exposed purified sperm to a 1.8 GHz phone-like signal for 16 hours, at doses from 0.4 to 27.5 W/kg (De Iuliis et al. 2009). Motility and vitality fell, oxidative stress rose, and DNA damage increased, significantly so from 2.8 W/kg, not far above the 2 W/kg torso limit. Crucially, they checked for heat. The signal warmed the samples by 0.4 °C at most, and the authors said heating could not explain what they saw.

In 2014 Fiona Mathews and colleagues at the University of Exeter pooled 10 studies covering 1,492 samples (Adams et al. 2014). Phone exposure went with motility 8.1% lower and viability 9.1% lower, the second result borderline. The effect on concentration was unclear, and the analysis mixed dish experiments with clinic studies based on self-reported use.

A dish isn’t a body

These results are real, but a dish isn’t a body. Sperm in a dish have no blood flow to carry heat away, and no skin, fat or clothing between them and the source.

The doses matter too. The Newcastle experiment ran for 16 hours straight at up to 27.5 W/kg. On one ruler:

SAR on one ruler · W/kg

Phones in the pocket test, and the doses used in lab studies

Pocket test (limb SAR, 0 mm, full power) · limit 4 W/kg

Typical phone (median)ANFR 2025, 80 devices

2.31

iPhone 12 after updateANFR 2023

3.94

iPhone 12 before updateANFR 2023

5.74over

Highest in 2025 checksANFR 2025

6.25over

07 W/kglimit 4

Doses in lab studies

Limb limit, for scaleICNIRP / EU

4

Highest dish doseDe Iuliis, Aitken 2009

27.5

Single animal studydrove Cordelli 2024 result

43.4

045 W/kg

Those aren’t all the same kind of SAR measurement, so treat the ruler as a sense of scale, not a like-for-like comparison. Dish studies show what can happen to sperm under lab conditions. They can’t tell us what happens in your jeans.

Does keeping your phone in your pocket affect fertility? The Swiss study

For real men, the largest study comes from Switzerland. In 2023 a team led by Serge Nef and Rita Rahban at the University of Geneva, with Martin Röösli of the Swiss Tropical and Public Health Institute in Basel, looked at 2,886 men aged 18 to 22. They had given semen samples when they signed up for military service, between 2005 and 2018 (Rahban et al. 2023).

Men who used their phone more than 20 times a day had a lower median sperm concentration than men who used it once a week or less: 44.5 million per millilitre against 56.5 million. That’s about a fifth lower.

The Swiss study · 2,886 men aged 18–22

Median sperm concentration, by how often men used their phone

Once a week or lessphone use

56.5 M/mL

More than 20 times a dayphone use

44.5 M/mL

03060 million/mL

The wording matters. In the paper’s own adjusted analysis, the clear result was a 21% higher risk of a total sperm count below the WHO reference value. The concentration result on its own was not statistically clear. So “21% fewer sperm” is not what the study found.

Then the twist. Keeping the phone in a trouser pocket was not linked to worse sperm. And the link with heavy use was strongest in 2005 to 2007 and weaker from 2008 to 2018. Röösli connects that fading to the move from 2G towards 4G, when phones began transmitting far less.

What the post said

Viral postaccount not shownClaim · paraphrased

Keeping your phone in your front pocket is quietly wrecking your sperm count.

Below the headline · what the study actually found

In 2,886 young Swiss men, carrying the phone in a trouser pocket was not linked to worse sperm; how often they used it was.

• Median concentration 44.5 vs 56.5 million/mL: more than 20 uses a day vs once a week or less
• Adjusted result: a 21% higher risk of a low total sperm count, not ‘21% fewer sperm’
• The link was weaker in 2008–2018 than in 2005–07, as networks moved towards 4G

SourceRahban et al. · Fertility and Sterility · 2023

The study

PEER-REVIEWED

The Swiss military-recruit study

WHO

Rahban, Nef, Röösli et al. (Geneva, Swiss TPH)

DESIGN

Cross-sectional; self-reported phone use

YEAR

2023 (samples 2005–2018)

n

2,886 men aged 18–22

The catch

Now the catch I promised. This study can show a pattern, but not a cause.

What the WHO reviews found

In 2024 the World Health Organization commissioned systematic reviews to pool everything, part of a programme involving Ken Karipidis of ARPANSA, Australia’s radiation regulator, who is also vice-chair of ICNIRP.

• Men in the real world. Kenny and colleagues found nine studies and rated the evidence “very uncertain”. For each extra daily hour of phone use, sperm concentration changed by +1.6 million/mL, with a confidence interval from −1.7 to 4.9: no effect shown (ARPANSA summary).
• Animals. Cordelli and colleagues found a drop in pregnancy rates. In a correction published in 2025, that result was rated high certainty but “largely driven by a single study” at an extreme dose of 43.4 W/kg. Without it, the effect wasn’t significant, and the authors called its relevance to humans “questionable” (corrigendum).
• Pregnancy outcomes in women. Johnson and colleagues looked at 18 human studies on preterm birth, low birth weight, miscarriage and more, and also rated the evidence “very uncertain” (Johnson et al. 2024).

The study

REVIEW

WHO-commissioned review: human studies

WHO

Kenny et al.

DESIGN

Systematic review of observational studies

YEAR

2024

n

9 studies

VERDICT

Very uncertain; no effect shown

ARPANSA’s summary page predates that 2025 correction, so for the animal result I’ve relied on the correction itself.

The better-established culprit: heat

Fertility researchers are much more confident about heat. Sperm are made a little below core body temperature, which is why the testes hang outside the body.

In one study of 656 men at a fertility centre, led by Mínguez-Alarcón and colleagues, those who mostly wore boxers had a 25% higher sperm concentration and a 17% higher total count than men in tighter underwear (ESHRE). It’s an association in a clinic population, but it fits the basic biology of how sperm are made.

Your phone does get warm, but that comes from its processor and battery, not the radio. In a 2019 lab test at KAIST on older Android reference phones (Nexus and Pixel), popular apps such as video chat pushed the surface past 50 °C in about 10 minutes (Kang et al. 2019).

Bras, bones and the one proven danger

Two quick claims you’ll also see.

• Phones in bras and breast cancer. This comes from a report of four women, aged 21 to 39, whose breast tumours sat directly under where they carried their phones (West et al. 2013). Four cases, no comparison group, no way to show cause.
• Phones weakening the hip bone. A study of 24 men who carried phones and 24 who didn’t found no difference in average bone density, only a side-to-side asymmetry (Saraví 2011). Tiny and cross-sectional.

But there is one proven danger from a phone right against the body, and it isn’t radiation. It’s the magnets. Held right over a pacemaker or an implanted defibrillator, a phone’s magnet can trigger the device’s magnet switch and put it into a different mode.

In 2022 a team led by Lacour, with Blaschke as senior author, studied 164 patients (Heart Rhythm 2022). The phone triggered the magnet switch in 30 of them, 18%, or almost one in five. On the bench, interference occurred in 85% of devices with the phone’s back facing them.

That’s why most device makers advise keeping phones at least 15 cm (6 inches) from these implants, and 30 cm when wirelessly charging. Apple and the FDA give the same figure.

The confidence meter

Here’s where each question lands, on the same scale as the earlier articles.

• Can a phone’s radio waves damage DNA like an X-ray?

  SETTLED· No: Decades of converging evidence

  Radio waves are non-ionising; their only proven effect on tissue is heating.

• Does keeping a phone in your pocket lower sperm quality?

  EARLY· Not shown: Signals, not answers yet

  The biggest study found the pocket didn’t matter, but it can’t rule it out.

• Is heavy phone use linked to lower sperm counts?

  EARLY· An association: Signals, not answers yet

  A correlation from self-reported use, mostly on older networks.

• Do the sperm-in-a-dish results apply to your pocket?

  DISPUTED· Unclear: Good studies disagree

  A dish has no blood flow or tissue, and doses ran far above real use.

• Does heat matter for sperm?

  STRONG· Yes: Consistent, well-designed evidence

  Sperm are made below core body temperature.

• Can a phone’s magnets interfere with a pacemaker up close?

  SETTLED· Yes: Decades of converging evidence

  It happened in almost one in five patients in a 164-patient study.

Scale: Disputed · Early · Strong · Settled. The word says how deep the evidence goes, not how dangerous something is. How the scale works

What I take from it

For context, no regulator says pockets are dangerous. ARPANSA says reducing exposure “is not considered necessary”; the UK suggests calling where signals are strong; France’s ANSES says to follow the distances in the phone’s manual.

Every source is listed below, so you can check my work. The video covers the same ground, and the earlier articles on 5G and AirPods build the ladder and the distance story this one relies on. I’ll keep reading the studies, one claim at a time.