Does niacin work for passing drug tests

About drug tests for cannabis and how they can be adulterated

About drug tests for cannabis and how they can be adulterated

The following articles deal with detection methods for THC and its metabolic products, possible causes of positive tests without drug use, the effect of diluting the urine, ingestion of substances that are intended to purify the urine, adding substances to the urine, influencing blood, saliva, and sweat Hair.

Cannabis users may be asked to take drug tests for a variety of reasons. These tests are generally done using biological fluids (blood, urine, saliva, sweat) or hair. For example, if there is a suspicion of driving under the influence of drugs, a screening examination of saliva or sweat can be carried out by police officers on site. If THC is detected in the blood during a possible subsequent examination of the blood, the person concerned is considered absolutely unfit to drive if more than 1 nanogram per milliliter of THC is detected in the blood serum. An examination of the urine or hair for THC or metabolic products of THC (especially THC-COOH) is often initiated by road traffic authorities when someone has been suspected of violating the Narcotics Act.

Presence of THC in biological fluids and hair

Blood: THC can generally be found in the blood for five to twelve hours after smoking a single cannabis cigarette. In the case of regular users, however, THC can still be detected in the blood after one to two days, possibly longer after the last consumption. However, the detection time of THC-COOH is often more than five days even after a single consumption. In general, however, the detection of THC in the blood is of interest, as this is supposed to prove acute drug exposure.

Urine: The detection time of a THC consumption in the urine fluctuates even more than the detection time in the blood. Extreme cases have been described in which habitual users had urinary drug screening positive for THC more than six weeks after the last use. On the other hand, even with regular cannabis use, drug screening can turn out to be negative after just one week, i.e. without drug evidence. Even though some unchanged THC is excreted in the urine, it is mainly metabolic products and mainly THC-COOH that is excreted. Therefore, the urine is examined primarily for the presence of THC-COOH. Depending on the dose and other influencing factors, THC-COOH can be detected in the urine for one to seven days after a single consumption, and generally around two to three weeks with regular consumption.

Saliva: In saliva, THC in particular is detected, which was deposited in the oral cavity when cannabis was smoked. The oral cavity is exposed to high levels of THC when smoking. Very little THC gets into the saliva from the blood. Metabolic products are also only detectable in low concentrations. If THC is eaten without the oral cavity being heavily exposed to the drug, for example when consuming THC capsules or by means of a badly chewed biscuit, the THC concentrations in the saliva are so low that it can generally not be detected. In one study, THC was detectable for between one and 24 hours in different people after smoking a cannabis cigarette. However, the screening tests for saliva are so imprecise that it is not uncommon for THC to be detected in saliva at all.

Sweat: Similar to saliva, drug screenings in sweat often do not give correct results. Nevertheless, these two forms of drug detection are intensively researched and further developed, since both liquids can be obtained from suspicious persons without great effort and interference with the personal rights of suspects in order to substantiate an initial suspicion, which could then be confirmed by a blood test.

Hair: There are several mechanisms by which THC and its metabolites can get into the hair. They can be built into the hair during hair growth, diffuse from the sebum or sweat into the hair, or be absorbed from the ambient air. The concentration of THC and THC-COOH in hair is very low and very variable. Hair rich in pigment (black hair) absorbs more of these substances than hair poor in pigment (blonde hair, gray or white hair in old age). In a study, THC or THC-COOH was found in the hair of 85 percent of all daily cannabis users and 52 percent of all non-daily cannabis users. In the case of infrequent use (once or twice a month), cannabis use is generally not detectable by a hair sample.

Detection methods for THC and its metabolic products

When examining urine, sweat or saliva, so-called "screening tests" are usually carried out first, usually as an immunoassay. These tests are primarily intended to answer the question of whether a certain drug has been taken at all. Often the test kits can detect several drugs at the same time. Screening tests, such as the EMIT (= enzyme multiplied immunoassay technique), are inexpensive, but less accurate than testing methods that are used to determine the concentration of a certain substance. Screening tests are used with a certain cut-off value to account for inaccuracy and not to have too many false positive tests. "False-positive" means that the test fails even though the substance is not present. In general, the test in the urine is negative (= no evidence of the substance) if you only smoked once or twice a week and did not consume it one or two days before the test.

If a screening test is positive, a more reliable method is used to confirm and determine the exact concentration. Usually this is a GC / MS (= gas chromatography / mass spectrometry), sometimes also an HPLC (= high-performance liquid chromatography). In principle, these tests are also used when blood or hair is examined for THC or THC breakdown products. These tests are also not exact, even if the analysis institutes are reluctant to admit this. Round robin tests conducted by the German Society for Toxicological and Forensic Chemistry in 2005 in German laboratories have shown deviations of sometimes more than 50 percent from the correct THC concentration in the blood serum.

Possible causes of positive tests without drug use

If THC or its breakdown products are detected, those affected occasionally claim that they have consumed hemp-based foods or have been passively exposed to cannabis smoke. In the 1990s, hemp oil in particular often had such high THC concentrations that tests for THC were positive after consuming such products.

However, manufacturers have responded, and today's products contain such low levels of THC that such claims are generally no longer credible today. In addition, the person concerned would have to indicate which product he used and in what quantities, and a fraud will be exposed as such at the latest when the THC concentrations in the product do not match the detected concentrations in a biological fluid. Passive cannabis use can lead to detectable THC concentrations in blood and urine, but only under extreme conditions and for a comparatively short time. Such an extreme condition exists, for example, when a motorist is traveling with three people who consumed cannabis while driving home from the Netherlands, because the low total air volume in the car can result in such a high concentration of THC that the non-consuming driver can do so too was able to passively inhale detectable amounts of THC. Claims that THC evidence is based on hemp food or passive consumption are now generally regarded as implausible protective claims, even if this may be true in individual cases.

Dilution of urine

A common method of manipulating urine tests is to dilute the urine. Increased fluid intake leads to dilution effects, so that the THC-COOH concentration is also reduced and can fall below the detection limit ("cut-off"). However, other natural substances normally found in urine - such as the concentration of creatinine - and the specific gravity of the urine are also diluted, so that excessive fluid intake can be detected. In addition, the urine looks very light-colored when it is very diluted, so that it is easy to suspect a dilution from its external appearance. By consuming large amounts of vitamin B2 (50 to 100 milligrams), which can be purchased as part of B vitamin products in the supermarket or drugstore, the urine retains a yellow color, even if diluted. By taking creatine (10 grams daily two to three days before the test), which is available at the pharmacy, you can prevent the creatinine concentration in diluted urine from dropping sharply. Creatine is taken, for example, as a dietary supplement by bodybuilders or used in medicine for muscle diseases (muscular dystrophy).

The more you drink and the more urine you pass, the greater the dilution effect.

In order to promote the excretion of urine, dehydrating agents (diuretics) are often used, which are also used, for example, to treat high blood pressure. However, the appropriate medication must be prescribed by a doctor. Weak dehydrating agents are coffee, mint tea, cranberry juice (from health food stores) and various other herbal dehydrating agents from the drugstore. If a urine test is scheduled for a very short time, cannabis users occasionally use strong diuretics such as Lasix (40 milligrams). You take the drug, drink as much water as you can, urinate two or three times, and then do the test. However, caution is advised when taking medication because in certain cases (pregnancy, breastfeeding, severe liver or kidney damage, insufficient fluid intake, potassium deficiency) they should not be taken. The first morning urine is the most concentrated and therefore also contains the highest concentrations of THC-COOH.


THC-COOH concentrations according to GC / MS analysis in the urine in nanograms per milliliter under various test conditions after oral ingestion of a uniform amount of THC-COOH (based on a study by Coleman 1997).

Ingestion of substances designed to purify the urine.

There is little scientific information on the effectiveness of commercially available products designed to clear the urine of THC and other drugs. They apparently work primarily through the amount of water to be consumed at the same time, i.e. the dilution effect described above. For example, 1.1 liters of fluid should be consumed when taking Quick Flush and 1.4 liters of fluid when taking Eliminator. Quick Flush contains B vitamins, creatine and plant substances (possibly diuretic plants). According to the instructions for Eliminator, one should eat and drink normally, then drink the whole bottle of Eliminator and additional water, then urinate 3-4 times and take the test after 45 minutes. The table shows the effect of dilution and the use of the two products on the THC-COOH concentrations in the urine according to a scientific study. By taking even larger amounts of water (3 to 5 liters) with appropriate dehydrating agents, the urine can be further diluted so that the detection limit can often be undershot, especially if the THC-COOH concentration would have been low without manipulation. It has no proven effect if the intake of larger amounts of liquid is started several days before the test, as this does not result in an increased excretion of THC-COOH. There is also no evidence that the intake of vitamin C, nicotinic acid (also called niacin or vitamin B3) or vinegar has an effect on the THC-COOH concentration. In theory, activated charcoal, which is also used for diarrhea, or lecithin could accelerate the excretion of THC-COOH. However, there is no scientific data on this. There is no evidence that commercially available products have a relevant influence on the excretion of THC-COOH, even if many users - probably due to the dilution effect - have had good experiences with it. Because there are also many opposite experiences.

Adding substances to the urine

Scientific studies have shown that the following substances are effective in preventing the detection of THC-COOH in urine in drug screenings: liquid soap, household bleach, table salt, caustic cleaning agents, vinegar and eye drops. Most of these substances may be noticeable through changes in specific gravity (table salt), pH value (bleach, vinegar), their appearance (liquid soap) or their smell. The influence on the test result may depend on the immunoassay used. The only substance that cannot be easily detected is eye drops. Scientists found that the preservative benzalkonium chloride in eye drops is responsible for falsifying the THC detection. A few drops seem to be sufficient to prevent the detection of THC-COOH in the urine by means of an immunoassay. Benzalkonium chloride is also found in many disinfectants and cleaning agents, such as Sagrotan. The detection of THC-COOH by means of GCMS is not affected by benzalkonium chloride.

According to a scientific study, adding papain to urine is said to reduce the concentration of THC-COOH without being easily detected in the laboratory. A commercial product (Urine Luck) contains PCC (pyridinium chlorochromate) as an active ingredient. It reduces the THC-COOH concentration in the urine the more the longer it can work. Some other commercial products appear to be able to falsify urine tests for THC or THC-COOH, including UrinAid, which contains glutaraldehyde, Klear and Stealth, which are powerful oxidants and can therefore destroy THC-COOH. With a targeted search for these adulterants, they can be discovered.

Affecting blood, saliva, sweat and hair.

As far as I know, the blood concentration of THC cannot be influenced. However, it is important to know that the blood tests are not accurate. In studies, eye drops also led to negative test results for cannabis in sweat tests. A product for falsifying saliva tests is also available on the Internet (, but its effectiveness has not yet been investigated. Since the THC concentration in saliva is mainly based on exposure to inhaled cannabis smoke, it seems quite possible that extensive rinsing of the mouth will lead to a reduction in the THC concentration. In general, however, there is no time to tamper with drug screenings in sweat or saliva.

Washing your hair extensively with some shampoos can reduce THC and its metabolites in the hair. In one study, washing hair with Head & Shoulders, Neutrogena, or Rave resulted in a decrease in drug levels. Based on theoretical considerations, it is likely that bleaching the hair with hydrogen peroxide, a powerful oxidizing agent, will lower the concentration of THC in the hair. When it comes to testing hair, it is important to know that armpit or pubic hair can also be used for drug detection if there is no scalp hair.

Dr. med. Franjo Grotenhermen employee of the nova Institute in Hürth near Cologne and chairman of the Cannabis as Medicine Working Group (ACM)

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