Apple Watch, heart rate sensors, and wrist tattoos: What you need to know!

Recently, we've been hearing reports from Twitter and Reddit that the Apple Watch's plethysmograph sensor plays not-so-nicely with wrist or arm sleeve tattoos. The ink pigmentation interferes with the sensor's ability to read your heart rate — and with it, the Watch's ability to assess whether or not it's maintaining skin contact.

After some brief tests, we're inclined to agree with those early reports — if your tattoo happens to be a solid, darker color. This is has to do with the way Apple measures your heart rate. Let's break it down.

The science behind Apple's sensors

Apple's support article (opens in new tab) on the Watch's heart rate sensor explains a fair amount about its inner workings, including how it measures your pulse:

Blood is red because it reflects red light and absorbs green light. Apple Watch uses green LED lights paired with light‑sensitive photodiodes to detect the amount of blood flowing through your wrist at any given moment. When your heart beats, the blood flow in your wrist — and the green light absorption — is greater. Between beats, it's less. By flashing its LED lights hundreds of times per second, Apple Watch can calculate the number of times the heart beats each minute — your heart rate.The heart rate sensor can also use infrared light. This mode is what Apple Watch uses when it measures your heart rate every 10 minutes. However, if the infrared system isn't providing an adequate reading, Apple Watch switches to the green LEDs. In addition, the heart rate sensor is designed to compensate for low signal levels by increasing both LED brightness and sampling rate.

In short, Apple uses various spectrums of light to track the blood flow through your skin. Anything that reduces that light's reflectiveness — ink pigmentation within your skin, for example — can interfere with that sensor.

For those wondering: natural skin pigmentation doesn't block light the same way artificial ink pigment or even scar tissue does, so you shouldn't run into a problem if your skin is naturally darker.

The Watch and tattoos

So does the Watch run into problems with wrist tattoos? Yes and no. I spent an hour today testing the Watch's sensor reading on multiple tattoo colors, and have indeed managed to replicate some of the issues Reddit and Twitter users were having.

For disclosure: We tested the Watch's sensors against tattooed and non-tattooed sections on both the wrist and elsewhere on the body. On non-tattooed non-wrist sections, the sensors gave identical readings as when also tested on the wrist; on tattooed sections, sensor readings varied wildly depending on colors and shading.

Dark, solid colors seem to give the sensor the most trouble — our tests on solid black and red initially produced heart rate misreadings of up to 196 BPM before failing to read skin contact entirely. Tests on lighter tattoo colors including purple, yellow, and orange produced slightly elevated heart misreads of 80 BPM (compared to 69 BPM on the wearer's non-tattooed wrist), but otherwise did not appear to interfere with skin contact registration.

When it comes to patterned or variegated wrist ink, however, we couldn't reproduce the misreadings or errors other users have been seeing. This may entirely depend on the type and design of tattoo, however, along with ink and skin saturation.

It's also worth noting that prominent scars and other potential skin aberrations can trip the Watch's sensors.

But I have a wrist tattoo! Can I not use the Apple Watch?

On May 1, the company published a followup to their support document (opens in new tab) with specific information about tattoos and other changes to your skin.

Permanent or temporary changes to your skin, such as some tattoos, can also impact heart rate sensor performance. The ink, pattern, and saturation of some tattoos can block light from the sensor, making it difficult to get reliable readings.

That said, don't panic just yet. For one thing, most full tattoo sleeves don't extend all the way to your wrist bone, which should leave space for the sensors. Additionally, if you have a wrist tattoo that extends to where you'd normally wear a watch, I suggest trying on a working unit to get a sense of whether your tattoo and the Watch interfere or not. (I'll also point out that Apple offers a 14-day return policy, which allows you to spend a fair amount of time wearing and testing the Watch.)

For those who have issues with their wrists and still wish to use the Apple Watch, you can turn off Wrist Detection in the Apple Watch app to avoid the device auto-locking; unfortunately, that will also disable Apple Pay from use. Alternatively, you might try wearing it on a non-tattooed wrist.

Updated on May 1 at 7:17 a.m. PT with Apple's statement in the help document on tattoos. // Updated at 4:30 p.m. PT to add information about scars, skin aberrations, and what you can do if you're running into these problems.

Serenity Caldwell

Serenity was formerly the Managing Editor at iMore, and now works for Apple. She's been talking, writing about, and tinkering with Apple products since she was old enough to double-click. In her spare time, she sketches, sings, and in her secret superhero life, plays roller derby. Follow her on Twitter @settern.

  • This is extremely disappointing. I am glad I didn't drop $350+
  • ....let alone $17,000
  • Yes, because you were so on the edge of your seat to getting one to begin with. lol
  • Well, it would be a simple return for anyone who did. It's also kind of a classic "Ordering a product without knowing a thing about how it works," situation for those with wrist ink that did so.
  • I imagine there is also a difference depending on the age of the tattoo and whether or not it was done with poor quality inks which typically include synthetics/plastics and probably create greater interference, or pure pigment inks,which are typically a mix of organic and mineral components that probably create slightly less interference.
  • I think you're spot on, and we're looking into this.
  • What about small lettered tattoos on the inside of the wrist of the arm you wear the watch on.... would that affect anything?
  • Do you have any evidence of what you say?
  • I don't have any evidence one way or the other as to how the differences in ink types effect heart rate monitoring with apple watch, other than a completely anecdotal and statistically insignificant sample of myself and my wife who both have tattoos with pure pigment inks and we do not have any problems with the heart rate sensor. This wikipedia article on tattoo inks offers a pretty accurate snapshot of what is in tattoo inks (although it doesn't make the distinction between inks that do and don't use plastics). Ink itself is not regulated by the FDA in the US, so unfortunately the only way to know what is in the inks your artist uses is whether or not they have a good relationship with the vendor they buy inks from, whether or not that vendor is transparent about their ingredients, and/or if your artist makes their own pigment based inks. My wife is a tattoo artist and I have work from her and the owner of the shop she works at, and they are very mindful of who they buy their inks from and they also make some of their own inks at the shop.
  • thanks! this is very informative. can you comment on what percentage of your customers have tattoos on their wrists?
  • Weird. The FitBit HR seems to use the same light technology to measure heart rate and I've had no problems on either arm (I have a sleeve on each arm). Obviously, they're different products from different companies, but it sucks that it's an issue for the Apple Watch (at least for now).
  • I really do think it depends on your tattoo. As I said above, we really only ran into problems with solid, dark colors whose ink had deeply integrated with the skin. Lighter tones and patterned tattoos didn't interfere much if at all.
  • Nice article, let's hope it doesn't affect hairy arms :D
  • Hairy arms are fine :)
  • Ty! I can't wait for my watch. I hope you guys do some Apple watch stand accessories review, I'm want to see the spigen stand
  • Plus as usual, Fitbit probably has the same very low number of tatooed people having issues not being reported on because insignificant, but this being Apple they nitpick at everything (bendgate anyone ?).
  • People are still getting tattoos? That's so 90's. :D
  • There was an episode of the TV show "Better of Ted" called "Racial Sensitivity", where the company had installed sensors for various things. The problem was, the sensors would not detect black people... When reading this news, I started to wonder if Apple Watch may have trouble with people with especially dark skin -- glad to see you mention that natural skin pigmentation doesn't cause trouble. (Apple would have a bit of a PR problem if it did!)
  • No. Apple Watch works fine on black people. Just not the heavily inked.
  • Loved that show- shame it didn't run longer.
  • Great show! The hilarious thing about that episode is that once they figured it out, instead of just taking out the sensors, each black person was assigned a designated white person to follow them around to activate the sensors. Then they had to hire more black people to satisfy their hiring quotas, who then needed more white people, etc. etc. Absolute shame that show didn't last longer.
  • I think you'd have to be pretty foolish to order an Apple Watch though if you had serious inking on your wrist. Why would anyone not immediately think this might be a problem? Luckily wrist ink is rare, and there's always laser ablation surgery.
  • No? I'm pretty sure most people don't actually know how the sensors worked. "I'm da Blur boys!" - Me with 1200 ping. Fiber in Nashville? Save me based Google.
  • Exactly this.
  • If they didn't know how the sensors worked (and I'm not talking detail here just the basic, functional facts), then they didn't even go so far as to read Apple's very simple web page describing the product. This would be like buying a car and then being upset that you have to put petrol in it, because "you didn't know that."
  • I was aware that it uses the whole light thing to function, but honestly who is going to see that and say "my ink might affect that." "I'm da Blur boys!" - Me with 1200 ping. Fiber in Nashville? Save me based Google.
  • Hrm. Seems like one of those things that should have come up in testing. I don't think it is the users fault, prior to articles like this, not realizing this could be an issue.
  • Agreed, but it's also not a problem with the Watch or Apple's fault. It is not possible to make any product to work in EVERY possible situation for EVERY possible person on the planet. They can return it.
    But of course the internet will turn it into #SleeveGate or #InkGate.
  • Well, anyone who knew about the heart rate sensor and had even a basic understanding of how it works should have known. That is, anyone who actually read the information or watched the videos on the thing before ordering it should have known.
  • Jeezus, that arm hair!
  • I guess that's one of many downsides you pay for covering yourself in tacky looking scribbles. Well, that and any chance of a good job or being able to speak to strangers without terrifying them.
  • THIS. People with tattoos can justify them all they want (personal expression, free country, etc.), but at the end of the day, there is absolutely no benefit to them whatsoever, can cause health risks if done improperly, and look increasingly bad the older someone gets. And for those who have tattoos to honor God, their mother, wife, kids, whatever, there are far more effective ways to do all of that than to deface your own body.
  • Benefit. They look nice.
    Benefit. I like them.
    Benefit. Permanent memories. Idk. Works for me. Of course u don't have many, but mine are for life events. I'll end up with more I'm sure. Also, mine are on my back and shoulders so this would never be an issue (the lack of an AW) ignored. "I'm da Blur boys!" - Me with 1200 ping. Fiber in Nashville? Save me based Google.
  • I can get a good job with my tattoos, and if you're terrified of me that's on you. Thanks for the judgement m8 "I'm da Blur boys!" - Me with 1200 ping. Fiber in Nashville? Save me based Google.
  • The amount of ignorance in this comment is baffling. Having tattoo's myself I can say with certainty that it has never affected my ability to secure a job and I can confirm, strangers have never ran off in horror when I walk down a street or attempt to talk to them in said job.
  • For those that for whatever reason can't make use of the Watch's heart rate sensor, one can Bluetooth connect a chest strap heart rate monitor to the watch...
  • But will that heart rate sensor read through my full-body Pat Benatar tattoo?? </s>
  • That solves the heart rate measurement but I'm not sure about the skin password lock.
  • Yes, and if for whatever reason they can't use the Watch's time display, one can use another watch on the other wrist
  • Tat-Gate!
  • No.
  • The solution for the moment for people with tattoos is that you can turn off Wrist Detection in the Watch iPhone app. This will mean that workouts keep on running, notifications come through and it stops auto-locking but also heart-rate monitoring doesn't happen automatically, sit/stand monitoring doesn't work and you still get notifications on your phone as well. I've had to do this because I've got a similar detection problem with my Watch, although I don't have any tattoos.
  • Also Apple Pay stops working when you turn off wrist detection.
  • Not in the UK yet, so 'luckily' that's not a problem right now for me personally. (But I really want Apple Pay to get over here.)
  • Forget the tattoos, what if the user has no wrists. Darn you Apple and your "wristedness"
  • i wish Imore would do an article on how this is the worst Apple has ever been prepared for a launch. in NY the watch pre-orders were available at 3:01 am .. my order went through at 3:03 for a Stainless steel 42mm with black sport band. 2 people i know that are right down the block from me placed their orders about 30-40 minutes after me and had their watches on their hands on the 24th. I got a 4/24-5/8 estimate and haven't even received a tracking number and still says "processing items". Another friend ordered the same time as me and got the Stainless steel with classic band and is having the same delays as i am. Terrible preparation this time around APPLE. This will make me think twice about waiting up to try to be one of the first ones to order their next product if im not going to be rewarded for doing so.
  • Agree 1000% If Apple could only have done the "order first, first in line" thing, I think they would get a pass on the fact that they didn't pre-make enough stock, as well as a pass from people like us on the fact that we aren't getting them for months. It's the fact that we stayed up half the night and ordered FIRST, but that many people who didn't and who ordered literally hours later got them BEFORE us. MONTHS before us. Add to that the fact that "special" people got watches handed to them without even having to order at all and the optics are just the worst. It's just so tacky and wrong. They could at least say sorry and give us a break on the price, or something.
  • Yeah, totally justifiable comment here, worst launch in history, people "down the block" from Anthony got their watch first. Maybe the Apple Gods just don't like you. And now that you wrote this stupid comment, hopefully they moved your shipment back further so we can hear you cry a little more.
  • i dont get the point of this reply? just to be a jerkoff douche? Over 1 million people ordered the watch and only 375k got theirs. btw i love internet tough guys. you would never be a wise ass like this to a stranger in person but once your in a nice safe place where nobody can slap the piss out of you your quick to be ballsy.
  • @Ronles: Most of the information we have is anecdotal because Apple keeps everything else secret. Beyond that, we do now know for a fact that they had a very low number of them manufactured before launch. We also know with a great degree of certainty that certain "special" people had their orders specifically expedited or picked out of the crowd to be processed first. Even with the anecdotal evidence, if someone posts online (and they have) that they ordered the exact same model of watch as I did, that they ordered it HOURS later, and that they now already have it in their hands, why would I not believe them? They don't know me and I don't know them. What's the argument for them being involved in some giant con to make Apple look bad?
  • "This will make me think twice about waiting up to try to be one of the first ones to order their next product if im not going to be rewarded for doing so." LOL What's the difference if you're waiting after you ordered or before you decide to order? You're still waiting. And if the anticipation is killing you, cancel your order. When was the last time Apple released a new product that you needed to think twice about waiting or ordering right away. Just about all new products hit a supply problem from overwhelming demand. It's just not feasible for a company to gear up for an initial release then scale back down afterwards. Supply is ALWAYS ramped up to meet demand and it will always be that way. As for Apple ruining your life because your friends down the street got theirs before you... Have you considered the possible issues and differences between your orders? I'm guessing you haven't. Did they order they same model/strap combination? Did they use the same credit card? Etc. Get a grip man. You've lived this long without it - I would hope you can live a little longer waiting for it to arrive? "Over 1 million people ordered the watch and only 375k got theirs" You don't know that. No one does except Apple. The rumored numbers are all over place. In fact, it was just reported that Apple pushed out over 600k by the end of March, which would mean they had many more on hand by the release date. Until Apple releases numbers, we don't know how many were pre-ordered and how many were shipped.
  • As someone with a tat on the wrist I appreciate you reporting in this. My left wrist is still untouched so I can work with this if I needed to. Sent from the iMore App
  • This is really unremarkable. Hemoglobin is a pigment. The Apple Watch looks for variations in the light absorbed by that pigment and correlates that with pulse. Tattoos are pigments. It only stands to reason that one would cover the other - especially if they're dark. You can't put on dark sunglasses indoors in low light and expect to see anything.
  • LMAO. Can't stand tats. Loosers lose again.
  • *losers. Guess my ink didn't affect my spelling ability. "I'm da Blur boys!" - Me with 1200 ping. Fiber in Nashville? Save me based Google.
  • moron.
  • Apple watches and tattoos are both not even on my Venn diagram.
  • It appears the people who are the most angry about this possible issue (the evidence isn't in, but the headlines sure are) are people without tattoos and are not interested in (read: vocally against) Apple Watch to begin with.
  • The take away I got from this is that some inks may cause trouble, and some may not, based on what the ink contains. So apparently people go around and let tattoo artists put ink containing unknown ingredients into their skin and that doesn't concern them a bit. But they do get worked up when the Apple watch doesn't work for them because of those tattoos that contain unknown ingredients in the ink? ...OK
  • Yeah, Inks aren't FDA regulated, so it's best to stick with an artist you're comfortable with that has a reliable connection with his or her source of Inks. And yes, you'd be surprised how many people are concerned about the lack of regulation, but also. How little people know. So there's that as well. "I'm da Blur boys!" - Me with 1200 ping. Fiber in Nashville? Save me based Google.
  • The issue of the Apple Watch not working as predicted in some instances where the individuals wrist is tattooed is not unique to the Apple Watch. Here's a quote from another post on the same issue. Click the link to read the full article. "But when you consider how Apple Watch gets those heart rate readings, this problem shouldn't be very surprising. This approach is one shared by other fitness bands including Fitbit's Charge HR and the Microsoft Band. The ink from a tattoo can dramatically complicate things for these devices in ways that natural human skin pigmentation never would".
  • This thread is so much more reasonable than the CBC one where people are contemplating if this issue is an indicator that the apple watch sensor has a racial bias against dark skinned people. *facepalms*
  • Apple (watch) is discriminating people and showing incorrect readings based on their skin tones. It is considered racial, showing incorrect readings based on ones skin tones(Fitzpatrick scale) cannot be accepted.
    Its a basic design flaw as the readings are not accurate and unreliable and affects the following.
    * The wrist detection feature does not work reliably
    * Apple(watch) think, you are an alien, and asks for passcode every time, because of this.
    * Apple Pay doesn't work.
    * Pedometer doesn't work reliably and pauses automatically.
    * The heart rate readings are not accurate and unreliable.
    What kind of tests apple did before releasing the "most personal device ever".
  • Where is your evidence of this? even clickbait articles like this one have been updated (but not in the url) to reflect their inaccuracy about the issue of skin colour:
  • Looks like I wont be getting one until this issue is cleared.