Are dual SIM cellphones more harmful than single SIM phones?


A dual SIM variant of your cell phone is almost a necessity in today’s hyper-connected age and times. A Dual SIM phone is seen to simplify lives for people who otherwise have to carry two phones. In this post, we access the risks of carrying a dual SIM phone on yourself.

From a Electro Magnetic radiation perspective, a Dual SIM phone have a significant double radiation effect. Cell phones give out radio frequency radiation (RFR) when communicating with cell phone towers. RFR is a non-ionizing form of electro-magnetic radiation. While the physical effects of non-ionizing radiation is negligible, doctors, public health specialists and many citizen groups believe that prolonged exposure to RFR can cause DNA damage, reduce sperm count, increase memory loss and risk of Alzheimer’s and even cause cancer.

Owing to fact that there are two SIMs trying to reach out to two sets of towers, increases the radiation emission by almost a factor of 2X as compared to a single SIM phone. Of the dual SIM devices that we have tested, we have seen the an increase in radiation levels from 40% – 80% in most of the dual SIM phones, as compared to their single SIM counterpart. Therefore prolonged usage of dual SIM phones are associated with enhanced radiation hazards.

Dual SIM handset categorization

Dual SIM handset categorization

Within dual SIM phones, there are 2 categories – Dual Active and Dual Standby. Dual Standby refers to a single radio unit that caters to both the SIMs and a Dual Active refers to a radio unit each for each of SIM (hence 2 radio units).Typically, dual active phones are used in case of different technology use cases i.e CDMA and 3G, 4G and 3G, CDMA and 3G whereas a dual standby phone combines SIM of the same or contingent technologies (3G + 3G, 3G + 2G, 2G + 2G). In a Dual Standby phone the radio is used by the two SIMs in turns – whereas in the Dual Active device both radios are working together. Therefore the totally radiating energy of dual active devices will theoretically be 2 times of a single device (it measures around 60%-80% higher); and, in dual standby devices the radiation could be around 40% higher than single SIM devices.

In the event that you are using only 1 SIM in a dual SIM phone, you are not cutting out the extra radiation. The vacant SIM Radio is still latching to the available networks (which allows you to call emergency numbers etc) – thereby increasing the radiation intensity. It may not be as high as loaded dual SIM devices – but it is still higher than a single SIM phone.

While we don’t prohibit use of dual SIM phones, we are listing out 6 must dos before you indulge in the purchase of a dual SIM phone.

1. Think clearly – do you really need a dual SIM phone. Is your desk phone at home or office not good enough for office use?
2. If at all you are buying a dual SIM phone, please indulge in purchasing from good brands – Samsung, Microsoft, HTC – are the ones we feel are the best in the lot. We advise against investments in Unverified Chinese handsets.
3. Please check the SAR value of the phone that you are purchasing. The SAR value in India is 1.6W/kg and your device should be as less from this number as possible.
4. Please necessarily use an earphone while talking on your Dual SIM phone.
5. Please donot carry your dual SIM phone in your trouser pocket. Please use a belt clip for carrying your dual SIM phone. Please use a radiation shielding phone pouch to reduce effect of RFR.
6. If you don’t happen to be using a particular SIM – please switch off that SIM. Some dual SIM phones allow you to set individual SIM settings.

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Do you really need a Dual SIM phone?

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Check SAR from the Dual SIM phones before purchase

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Purchase Dual SIM phones only from trusted OEMs

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In case one SIM of a dual SIM phone is not required to work – change dual SIM settings and close the SIM not required

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Dont carry your dual SIM phone in trouser pockets absolutely

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Please use an earphone during a call on a dual SIM phone

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Tags Are dual SIM more harmful than single SIM phones?Dual SIM phones have a significant double radiation effectProlonged usage of dual SIM phones are associated with enhanced radiation hazards.


  • Pravin Maheshkar /

    nice informative article

  • Mohanachandran /

    It is a useful n important information. unfortunately most of the public are not aware of it.
    BUT just like, smoking is injurious to health.

  • Hello, if I use only 1 sim card on a dual-sim phone, will I be exposed to a higher radiation level?

    I have heard that phone emits radiation even without a sim card. So does that mean that dual sim-card is a dual radiation exposure even no sim cards are inserted?

    • Dear Madam

      Thank you for your comment.

      You are right. A cell phone latches on to a telecom network even when the SIM is not inserted. (That allows you to make emergency calls from cellphones without SIM Cards).
      Theoretically, if you have a dual SIM phone, the phone radio is working double times over to connect to the network – therefore double radiation.

      Also, if you use 1 SIM on a dual SIM phone and keep the other SIM slot vacant, it reduces the radiation by some amount (as compared to 2 SIMs in the 2 SIM slots), but it is still higher than a single SIM – single slot cell phone.

      The key is to maintain a distance between the phone and yourself. The best way to do this is to use a handsfree headset or a Bluetooth headset. Brightsandz has a range of 0 EMR headsets and Bluetooth. You can check it out on the site

      Team Brightsandz

  • Hi,

    I want to buy Microsoft Lumia 650 Dual Sim LTE for my Mother. Now I’m not sure it’s safe?

    • So if I buy it then the phone will be emiting the same amount of waves as single sim phone, when I insert 2 sim cards, and switch one sim card off by turning plane mode on, on one of them?

      • Yes.
        If you use a dual SIM phone it emits atleast 40% higher radiation than a single SIM phone. If you insert 2 SIM cards but switch one off by turning airplane mode on, then the phone radiation is much more controlled.
        Team Brightsandz

        • Thanks, Could You look at this?

          This site says that SAR is bigger in Microsoft Lumia 650 LTE SIngle Sim, than in Microsoft Lumia 650 LTE DUal sim. Strange right?

          I can’t seem to find another source of info about SAR for this those two phones.

          I wanted a dual sim for my mother because I wanted her to have a free internet and cheap calls, both offers come from to different companies, so she would turn the pane mode on when she’s not using internet. So on the sim for calls it would be 2G, and for the other 3G, but mostly plane mode.

          • Hi
            We routinely refer to the same site for phone SAR specs.
            Your question, your reasoning and the available data on SAR value of Nokia Lumia 650 Dual SIM and Single SIM leaves me baffled as well. I did a vigorous spec to spec check and i find that Dual SIM Lumia 650 operates on more frequencies than single SIM Lumia 650. Apart from that both phones are absolutely the same physically, spec wise and in every other respect. This means that the Dual SIM phone should have higher SAR as compared to single SIM phone.
            I didnot find any reference on Lumia site as well.

            Given all these, there is a far shot that Lumia antenna placement and architecture differ for DUAL SIM and SINGLE SIM phones. Somehow they have a better antenna architecture in dual SIM phone which leads to lesser SAR. I am not sure about this though.

            Regarding dual SIM phone purchase for your mom, your usage is very efficient. That is the way phones need to be used. Switching of Data SIM not only reduces SAR but also saves data that apps leak to the cloud.

            Thanks for a great discussion. You can write in to us at or as well


        • You say
          “If you use a dual SIM phone it emits atleast 40% higher radiation than a single SIM phone. If you insert 2 SIM cards but switch one off by turning airplane mode on, then the phone radiation is much more controlled.”
          So using a single sim phone 100%, using a dual sim phone 140%.

          So if I turn one of those sim cards into a plane mode, what will it be compared to a single sim phone? The same? 110%?
          I tried to turn plane mode in my singe sim phone SOny Xperia Go, and then a typed alarm number in Europe 112, and it made the call. So what hapenned? Was the transmission started after I used the alarm numner? or was it there contineusly?

          • Hi
            Dual SIM phones without the SIM still talk to the network. A phone in air plane mode is as good as a dead phone. It doesnot connect to the network at all. Or so i thought – till you claimed that you made a call on offline mode to EUROPE 112 on a single SIM phone. Airplane mode switches of WiFi and Bluetooth as well. Technically 2 SIMs with one SIM in airplane mode will be equivalent to single SIM phone only (100%).
            I am not aware how your phone on Airplane mode made a call to the network. I would think it to be technically improbable.
            Normally phones are in touch with the network every few seconds/ minutes interval beaming availability. Even if you are not on home network, your phone would be connecting to other networks. Emergency number calls are prioritized on all networks.
            However, i am at a loss again, why would your airplane mode device connect to any network. Beats me!

          • Thanks, great discussion!

            My friend told me that, She thinks like You, that the dual sim version is probably more modern, probably Microsoft did that to limit SAR values.

            As for the 112 call in the air plane mode, we think that when You switch air plane on, and then type 112, then the air planemode automatically switches off as soon as You make that call by tapping “call” button.

            Thanks from Poland 🙂

          • It has been a great learning for us as well. We are extremely pleased that this discussion was of help to you. Please donot hesitate to send us any more discussion threads. It good to be learning with people like you

            Team Brightsandz

    • Hi

      Microsoft Lumia 650 dual SIM has a .98W/kg head SAR and .65W/kg body SAR. both values are within the safe zone. It is safe to use the phone. Additionally we advise you to please use this phone with earphones for enhanced safety.

      Team Brightsandz

      • Right now we are both us are using Sony Xperia Go, it’s a single sim phone, but I think new phone wether it will be Microsoft Lumia 650 Dual SIm or MIcrosoft 650 single sim it wil be lower.

        • As i said earlier, since we dont have a means to ascertain DUAL SIM LUMIA 650 SAR is really lower than SINGLE SIM LUMIA 650 SAR. However, given your usage habit (voice and data SIM different, Data SIM on airplane mode when not in use), i think Dual SIM LUMIA 650 LTE looks good. Its absolute value SAR is also within permissible limit.

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