Medically Reviewed by
Jason Crawford

Article Last Updated on January 11, 2023

Have you smoked weed recently? Are you afraid it will show on your mandatory drug test at work? Do you wonder how long weed stays in your system after consumption? Or whether you have enough time to detox your body before the big test? We will answer all these questions below, as we dive further into what niacin is and how people use it for detoxing.

Let us first tell you that there is no magic pill you can take that can instantly detox your body in order to have a clean test. But there are ways that may help you release THC metabolites which are stored in the fat cells inside your body. 

If mandatory drug testing for employees is required at your workplace and you use cannabis, you probably want to detox your body before taking the test. One of the ways to do that may be by using niacin. Keep in mind, however, that we’re not recommending cheating on drug tests. This post is purely for informational purposes only.

Cannabis Drug Tests and THC Levels

Drug tests measure the levels of cannabinoids in your body, the most common ones being:

  • Urinalysis (this urine drug test is done by taking a urine sample and analyzing it for the presence of carboxy-tetrahydrocannabinol (THC-COOH), which is a metabolite released after tetrahydrocannabinol (THC) has been processed by the body);
  • Blood test (this type of drug testing is the second most common way to test for drug use, and it’s done by checking blood samples for THC presence);
  • Saliva test (this is a less invasive drug test and it involves taking a swab of saliva and testing it for the presence of drugs);
  • Hair follicle test (this type of test has one of the biggest windows for detecting drugs and users could test positive for up to 3 months after they have consumed weed).

Drug testing laws may vary from state to state, so if you want to be sure that you’re clean for your mandatory workplace testing, you may want to do a home test beforehand.

Depending on whether you are a heavy smoker, or you use weed occasionally, niacin may help your body detox.

What Are Niacin Pills?

Niacin or vitamin B3 is a nutritional supplement that is sold over-the-counter. It’s also known as nicotinic acid and is mostly used to manage niacin deficiency. Niacin deficiency, or pellagra, is a disease caused by a lack of vitamin B3 that manifests with mouth sores, dementia, inflamed skin, and diarrhea. 

Generally, these supplements come in the form of 500 mg pills. Apart from treating pellagra, they are used to treat hyperlipidemia or high cholesterol. The recommended dietary allowances (RDA) for niacin are 14 mg a day for women and 16 mg for men when niacin is taken as a supplement. But when you use it for detoxing purposes, the doses are higher. People who suffer from diabetes should avoid using niacin without a note from a licensed physician.

How Is Niacin Used for Detoxing?

When using weed, THC builds up in the fatty tissues in your body. As a result of cannabinoids being stored in body fat, when detoxing they are released through urination and sweating, therefore they can be detectable in blood, urine, and hair for a long time. 

Niacin increases the body’s ability to burn fat and detox THC by dilating the blood vessels and flushing the THC out of your system faster.

How to Do a THC Detox With Niacin Pills?

Below are the steps on how to detox with niacin. Keep in mind that this is for educational purposes only,

  1. Pause drug use for a few days.
  2. Take 500 mg of niacin with two glasses of water in the morning.
  3. Stay away from fatty foods and drink plenty of water with electrolytes.
  4. Take another 500 mg of niacin every six hours, but not more frequently than that.
  5. On the day of the test, get up early and consume 2 pills within 6 hours between both.
  6. Take a B12 supplement to get natural-looking urine and take a small dose of creatine in order to replenish creatinine levels before the test.

Flush Free Niacin

People take these types of pills to avoid flushing, although using this kind of niacin pills can have other side effects. Flush free niacin can be a cause of liver toxicity and a lower ability to manage cholesterol. This type of B3 that can come from inositol hexanicotinate isn’t a good detox option because it can’t speed up fat-burning, and some sources even suggest that it’s a marketing scheme. If you decide to use niacin, make sure that you use the regular flush method to detox from weed.

What Are the Side Effects of Using a Niacin Detox?

While low doses of niacin aren’t known to cause any side effects, high doses of niacin can cause a niacin overdose and a number of other unwanted conditions and life-threatening situations.

According to scientific evidence, detoxification with a high amount of niacin can cause niacin toxicity which is a condition where people have large doses of niacin in their bodies and experience side effects.

Some of the side effects of high-dose, long-term niacin therapy include ischemic stroke, insulin resistance, hypotension (low blood pressure, dizziness, fainting), hepatitis, hepatic dysfunction heartburn, glucose intolerance fatigue, cerebral hemorrhage, etc.

What Else Do People Use?

Apart from using niacin to evade a positive drug test, some cannabis users also mask their urine samples with salt or bleach. They use detox products like detox drinks and cranberry juice, as well as submit synthetic urine.

There is no way to know whether these methods work since further studies need to be done to research them. For the time being, it’s safe to say that people should stick to abstinence before their drug test in order to get negative test results.

Drug Testing in the Workplace

Since the War on Drugs, mandatory drug screenings have been a common occurrence among many companies around the world. As a result of that, many recreational marijuana consumers fear getting positive drug test results and turn to niacin.

If we look into the most common testing methods we’ll see that each individual testing method varies in terms of the time frame in which it has the ability to detect the presence of cannabis:

  • Urinalysis – done by taking a urine sample which can result in a positive test after 5-7 days for moderate marijuana users, and even more than a month for heavy chronic users. This is the most common method of workplace drug testing.
  • Blood test – done by examining a blood sample which can detect THC levels up to a week after cannabis use.
  • Saliva test – has a detection window of up to 72 hours after initial cannabis use.
  • Hair test – has the highest detection period of up to 3 months.

When testing, testers look for the presence of 11-OH-THC (the main active metabolite of tetrahydrocannabinol) and THC-COOH (the second metabolite of THC that’s formed in the human body after cannabis is used).

How Long Do You Have to Take Niacin for It to Flush Weed Out?

Finally, let’s get into the subject of how long it takes for niacin to flush the weed out of the body. Keep in mind that this method may not work for heavy users who use large amounts of cannabis, but may work for occasional marijuana users.

You can do a THC cleanse by using the following steps:

  1. Stop using drugs until your test and start your 3-4 day niacin flush.
  2. Take 500 mg of niacin every 6 hours leading up to your test accompanied by plenty of water.
  3. On the day of the test, take two pills within 6 hours between them.

It’s important to remember not to consume more than 2 grams of niacin per day, and also take some salt or electrolytes in order to replenish the vitamins lost during the detox. People that do this method also benefit by taking a supplemental dose of creatine in order for the creatine levels to measure correctly on the day of the test. Some people even decide to do a home THC test prior to taking the test at work as a preventive measure.

Niacin RDI for Adolescents and Adults

Niacin is naturally found in a lot of foods we consume on a daily basis. You can find it in pork, beef, whole-grain cereal, cow’s milk, and eggs. While people generally get their RDI (Recommended Dietary Intake) from foods alone, sometimes supplementation is necessary. 

As we’ve mentioned above, niacin deficiency can be the cause for the development of the disease pellagra which is an inflammation of the skin presenting itself as a rash as a result of sun exposure. The use of niacin as a supplement is very common in such cases.

The recommended dietary intake (RDI) for niacin in different age groups is the following:

  • Adolescent boys aged 9-13 years – 12 mg/day;
  • Adolescent girls aged 9-13 years – 12 mg/day;
  • Adolescent boys aged 14-18 years- 16 mg/day;
  • Adolescent girls aged 14-18 years – 14 mg/day;
  • Adult men over the age of 19 – 16 mg/day;
  • Adult women over the age of 19 – 14 mg/day.

Where Can You Buy Niacin Flush Pills?

Prescription niacin can be bought as an oral tablet or an oral extended-release tablet. You can find it under the brand-name drugs Niaspan and Niacor. Niacin is also available as an over-the-counter medication which can be purchased in settings where you can get advice on the intended use and adverse effects by trained healthcare providers.


To sum up some of the important points in this post, below are some quick questions with quick answers.

Q: What is a niacin flush?

A: A niacin flush is a common side effect of taking niacin supplements in higher doses. It consists of reddening of the skin, tingling, burning, itching, and/or warm skin.

Q: How long does niacin flush last?

A: A niacin flush can occur anywhere from 10-15 minutes to half an hour after taking niacin, and can last anywhere from a few minutes to an hour or so.

Q: How long does niacin stay in your system?

A: Niacin stays in the system for about 2 to 4 hours.

Q: How much niacin to flush THC?

A: As covered in this article, you can take 500mg of niacin every six hours (for 3 to 4 days) if you want to flush out THC from your body.


In order to test negative on a drug test, a lot of people turn to niacin. But, although it may help your body detox faster, it may not work for heavy users who use large amounts of cannabis. Your best option would be to seize drug use, let your body detox naturally, and take a home test to check your THC level.

A passionate advocate for the benefits of cannabis. Fraser Horton, who has a background in botany and a strong love of nature, has spent years researching how cannabis affects the body and mind. He established Leaf Nation in 2020, where he has devoted himself to educating people about the legalisation of marijuana and its safe and responsible use. Fraser is committed to highlighting cannabis’ potential for improving wellness and working to dispel the stigma associated with its use.


The information presented on this page is provided as a public service to aid in education and is derived from sources believed to be reliable. Readers are responsible for making their own assessment of the topics discussed here. In no event shall Leaf Nation be held reliable for any injury, loss or damage that could happen if using or abusing drugs.