How can I drug test without someone knowing?

Surface and visible substance testing can help you drug test someone without their knowing. So can drug screens using hair samples. But testing for drugs without consent is not recommended. More on drug testing without someone knowing here.

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Can you test a person for drugs without their knowledge?

The answer is yes and no. It is quite easy to test for the presence of drugs in a room or area without a person’s knowledge and it is technically possible to test someone for drug use without their knowledge, but it is not recommended. In fact, if you are asking, “Is my child on drugs?”, have someone close who is in recovery from drug or alcohol addiction or suspect that your partner or loved one is using, drug testing is best completed when consent is explicit.  And helping your husband with drug addiction (or your wife, or partner, or child) requires more than just confrontation or intervention.  Still, we discuss the particular methods for drug testing without consent here, and invite your questions about drug testing in the comments section at the end.

Surface substance testing

What many drug users (and people in general, really) don’t know is that after you handle drugs, you leave a trail of invisible drug residue on the surfaces you touch. These surfaces include: computers, phones, vehicles, clothing and just about any other surface. You can’t see this residue but you can test surfaces to see if any of it is there (which means you don’t need the person who is leaving the residue behind to be around when you test it). So how does it work?

Typically, surface substance testing involve wiping down a surface with some kind of small testing device and then instantly performing the test. Often this involves using tap water to make the test work. They all come with their own detailed instructions. You then read the test (they usually use lines like a pregnancy test) to see whether or not traces of drugs are present.

What does surface substance testing screen for?

You can get surface and visible substance tests that detect only one or two drugs or you can get more comprehensive ones that test for five or more drugs. But one thing that is important to keep in mind is that these tests will merely tell you if drugs are present on that surface. This test cannot tell you if someone is actually doing drugs (although some of them can be used to test people’s sweat for drugs). However, if you are trying to maintain a drug free household or workspace, naturally drugs shouldn’t be on any surfaces and you’ll know you have a problem if you find them.

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Drug testing visible substances

A slightly different kind of test allows you to determine if a substance contains drugs. So, if you can actually see some kind of powder or some other substance that you’re not sure of, you can take a sample of it and use one of these tests to determine if it is a drug or contains any drugs. You can also test a substance you are familiar with (such as toothpaste, for example) to see if it contains drugs. Keep in mind, though, that these tests can only determine if a substance is a drug or contains drugs and not if a person is actually doing drugs.

Where to buy surface and visible substance drug tests?

There are a number of different surface testing kits and substance testing kits on the market that are relatively inexpensive. And while you do get the advantage of instant results with these kits, also keep in mind that they have expiration dates and that they have to be kept and used within a certain temperature range to maintain their validity.

Hair drug testing without someone knowing

I was a bit torn on whether or not to include hair testing in this entry but I decided to include it for informational purposes. It would be technically possible to collect samples of a person’s hair and have that hair tested for traces of drugs without their knowledge. However, this is discouraged by the laboratories that perform these tests for a number of reasons.

The most obvious of those reasons is because it is considered to be an invasion of a person’s privacy to send their hair away for drug testing without their knowledge. Another big reason it is discouraged is because there is no way of knowing 100% for sure that the hair you’re gathering from a person’s hair brush or pillow or wherever else it is collected is from the person you think it belongs to (hair travels quite well on people’s clothing and people do share things like hair brushes and pillows on occasion). Yet another reason it is discouraged is that a hair sample collected in this way won’t be consistent, unlike one collected in the usual manner.

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Because I’ve already mentioned hair testing, I will give you a quick overview of it.

How do hair drug tests work?

When drugs enter an abuser’s system, they are metabolized by the body, creating tell-tale metabolites that are distributed throughout the body by blood and leaving traces in the body’s tissues, like hair follicles. The metabolites then stay in a person’s hair follicles and laboratories can detect drug use up to 90 days prior to the sample being taken (a half of an inch for every 30 days). A big advantage with hair testing is the amount of time you can test for. Ninety days will give you a pretty comprehensive picture of recent drug activity.

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As far as the actual testing goes, on your end, all you have to do is collect a sample, place the sample in the collection pouch that is provided with the testing kit, seal it and send it to the lab. Each kit will come with its own detailed instructions on how to collect a sample. The laboratory will do all the actual testing.

Collecting the sample involves cutting a small chunk of hair off the person’s head as close to the scalp as possible. Anywhere from 40 – 100 strands are needed depending on the type of hair being tested. All the strands of hair need not come from the same area on the head. You can gather them from different areas. You can also use body hair.

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Can you cheat on a hair sample drug screen?

No. Hair testing has some big advantages over urine and saliva testing. Probably the biggest advantage to testing via hair follicle is that it’s virtually impossible to cheat. Because the laboratory is testing the very molecules the hair is made of, no shampoo or anything else marketed to beat hair drug tests have any effect on them. Even dyes and other things that manipulate the hair don’t change it on a molecular level.

Disadvantages of testing for drugs using hair

Hair follicle testing does come with some disadvantages, though. Two of those are the time frame involved with the testing itself and also how long it takes for drug traces to show up in the hair.

Because hair follicles need to be sent to a laboratory, immediate results are not available. Typically, a lab can get results back to you between 7 – 10 days. Some labs have the option of fast-tracking your sample for an extra charge for a turnaround of only a couple of days.

Also related to time, it takes about a week for traces of drugs to show up in a person’s hair so if you suspect a person of having done drugs on a particular day, you will have to wait a while before collecting the sample.

Where to find hair sample drug test kits

There are several hair sample test kits available on the market. There won’t be much to the kits themselves, probably just instructions, something to hold the specimen, an envelope to put it in, a security label and maybe one or two other small items. Keep in mind when comparing prices that it’s the lab work that you’re really paying for, not what is included in the kits themselves.

Should I drug test without someone knowing?

The decision to drug test without consent will be yours. No type of testing, though, takes the place of good, old-fashioned open communication and mutual understanding. But it’s good to know that these tests are there if you need them.

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About the author
Lena Butler is a mom, health blogger and customer service representative for TestCountry. TestCountry is a San Diego based point of service diagnostic test service provider that offers a wide range of laboratory and instant testing kit solutions including drug tests, metal toxicity, DNA paternity, food and water tests and hundreds more. TestCountry's tests are easy to use and can be performed at your home or workplace.


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  1. I started working for a family friend with whom I have known since I was in my late teens. I am now in my mid 30’s and have worked for her close to a year and have rented a room from her for about 6 months. I am currently on probation for a felony which she is aware of. Well about a month ago after my car was broken into while parked in our driveway she bought a bunch of security cameras. It wasn’t until about 2 weeks later that I found out she had hidden cameras in the house as well, and she won’t tell me where they are. Then I noticed that the plumbing was acting weird. Like when I turn the faucet off the water keeps going for a good 15-20 seconds…and every time I flush the toilet it sounds like it’s making a gargling noise. Not only that but she or her husband wait until I get home and go into my room and they proceed to do something in the bathroom that only I use every single time I get home. I’m talking it could be 2am and one of them will get up to go in the bathroom before I can use it and they will do whatever it is they do. I did find an entire box of 5 panel drug tests along with cups and gloves, which had all Bern opened and used. But they have never one time asked me to test for them. Is there some way they could be collecting my urine and testing it even though I’m flushing it? I feel like I’m in the twilight zone and I’m going crazy from the anxiety knowing that I am constantly under a microscope but now to think they are testing me…is it even legal to drug test someone without their knowledge or consent? PLEASE HELP!! I AM DESPERATE FOR ANSWERS BEFORE I LOSE MY MIND!!! Thank you in advance!

    1. Hi Jessica. If you suspect that something is wrong, I suggest that you talk with your friend. Also, you may consider finding a new place.

  2. I really like these tips that you shared for drug testing without people knowing. This is something that I have been thinking about with my teenager. At the same time, I feel that he should face the consequences if he did do something he shouldn’t have. Maybe I should look into drug screening services that can help me out.

    1. Hi Theresa. First, you may ask for surface drug tests in local pharmacies. Then, you may buy it from the Internet, and have it delivered on your address.

  3. Hair drug testing is a very good idea without someone knowing. Unlike urine test, it gives accurate results because in this testing no one can cheat especially at workplace this testing is gaining popularity. Thanks for providing such wonderful information.

  4. Dyeing your hair DOES NOT affect the drug test results for a hair test. AT ALL. My friend works at a testing center and she told me it absolutely doesn’t work to dye your hair.

  5. Where can I purchase a hair follicle test and the cheapest but good one? Where do I send it to and how much is it to be tested? Have a family member that I found a metal container with a white substance and a small cut straw in the container. I am very worried.

  6. I have something in a bottle that looks like drugs. Is there a product that can tell me if it is in fact some sort of drug and what it is?

    1. Hi Cheryl. I suggest that you speak with a toxicologist or another professional who can investigate the substance.

    1. Hi Educated. I believe that you can have an open communication with a drug addict. They are humans after all. You just need to find a way on how to establish trust with that person, and then, open communication comes naturally.

    1. Hi, Trey. Hair dyes, bleaches, and treatments may affect the drug results. But, keep in mind that drug tests also use hair body (pubic hair or skin hair) for a hair drug test.

  7. My sons Girlfriend has been doing drugs for the last two months she dyed her hair yesterday he’s wanting custody of his son she has been running other men and he wants out my Question is once you dye your hair can they still detect drugs in the follicles she was swallowing gel strips to counteract the withdrawals

  8. My husband and I believe our son is using weed, but he won’t take a urine test. He has use pot in the past, and we are at our wit’s end. Please, can you help us figure out a way to do a swab on his computer? He is a junior in college, and he could lose so much, but he won’t listen to us. Please, we need help before it’ s too late.

    1. Hi, Sonda. I believe you need a drug testing kit that is designed for testing surfaces.You can get it at a pharmacy or order it online.

  9. I have concerns that my soon to be ex wife with personality disorders may be using Cocaine or MDMA around my infant son whom she has full custody of until further court dates. It’s very difficult for me to gain access to her room, although I am there occasionally. What would be the best way to test for drug usage? I like the hair idea, but not sure if I can get 40 different pieces of hair.

    Thanks for your input.

    1. Hi David. The hair test can be done if you can obtain hair from her brush, otherwise there would have to be a court order for her blood and urine to be tested.

  10. Tucka I’m in a similar prediciment many years ago me and partner used love living a crazy life drugs played a big part but also with crazy came th arguments and fights until we both decided enuf was enuf and wen to 0% intake anything other than jst a beer years hav gone by and we’ve build a secure family life and hav always been vry much connected ( if u no wat I mean ) that was until wat I believe is th last 12 months and we’ve spoke argued split not spoke u name it but he swares he’s not taking nothin but being a pretty clued up open minded person in general and been there dun it I no th tiny things that change instantly and ova a period ov time ex sample personality aprouch ect and I NO dispute wat he says I am right it is constantly nigglin and th more alert I am th more sure I am in fact evry part ov me is tellin me he is .if I am wrong I will amputate my legs I feel I hav gone back 9 years but only reliving th jeckle an hide part my point being u hav th thought and feeling because u hav once been that thought and feeling but it’s not until they are replaced with reality and reall thoughts and feeling are u able to separate them but still be able to identify each full with out a doubt , u hav been given a reason to think sh having a bit more than sh says because Sh is !! U don’t create th idea ov ur thoughts unless ur given a reason to think ov it in th first place Don’t doubt wat u feel to be is true xx hope u can sort it

  11. Tucker that smell is exactly what you think it is. Don’t get played. She’s smoking crack for sure. Nothing else smells that way. Nothing.

  12. I have a question…for many years I was addicted to cocaine in every form. The most addictive was in the freebase form and I spent many terms in and out of jail for trying to support the addiction and I was finally “freed” from the addiction in 1996. I never will forget the smell of it. My current girlfriend smokes Marijuana out of a little one hitter but every once in a while I get that odor as she is smoking and I swear she has some mixed with her weed. I try to talk with her about it but it just becomes a fight. It is so strong I swear I’m right, as I say you never forget that smell. How can I test the residue in her hitter to see if I’m right??? Please help. I don’t ever want to fall back into that, or want it around me.

    1. Hi Tucker. There are drug testing kits that are designed for testing surfaces. You can get it at a pharmacy or order it online and gives a certain colour if it gets in contact with a surface where cocaine has been present.

  13. I was drugged and the drug dealers drugged me to put me to sleep I slept for about 20min. wasn’t sleepy at all but I got to drug testing place they ONLY found my medicine NO Not even my medicine only two and I had taken phengan and more. tell me what did these horrible folks do

    1. Hi Jane. Are you Ok? You need to report this to the police ASAP and give a detailed description of these men so they can be caught and brought to justice.

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