Do Drugs Show Up in Blood Tests? (6 Detection Factors)

A person holding two test tubes filled with blood for blood testing

When drugs or other addictive substances are ingested, they become absorbed into the bloodstream, which makes them detectable during any drug testing procedure.

Different drugs have various time frames in which they will register on a blood test with varied accuracy rates.

After conducting months of thorough research, I can now tell you which drugs are detectable in blood drug tests and the factors influencing how long they stay detectable.

Quick Summary

  • Various factors influence how long drugs remain detectable in a person’s bloodstream.
  • Blood testing typically reveals the presence of drugs more quickly than other sample types, such as oral fluid or a urine sample.
  • Employers conduct random screenings of workers or mandatory testing before someone is hired for a job to detect drug use.

What Drugs Can Be Detected Through Blood Drug Testing?

A close up shot of a hand holding a test tube of blood ready for blood drug testingDrugs that can be detected through blood drug testing are alcohol, amphetamines, including methamphetamine, barbiturates, such as phenobarbital and secobarbital, and benzodiazepines, such as alprazolam or clonazepam. 

Other drugs include cocaine, marijuana (THC), opioids, and opiates, such as heroin, codeine, oxycodone, morphine, hydrocodone, fentanyl, Phencyclidine (PCP), prescription drugs, and steroids.

Several types of drug tests can be used to identify certain drugs. Urine and saliva tests are more common; however, blood drug testing is ideal in particular situations because it can detect substance use faster than other sample types like oral fluid.

While it’s advantageous for quick results, a downside of this method is that it can only detect short-term usage.

On rare occasions, obtaining a blood sample may not be possible due to difficulties with venous access [1]. In these instances, another reliable drug test, such as hair testing, will take its place.

Blood Drug Test Results Detection Times

A doctor examining blood sample

Blood tests are designed to detect the parent drug of a particular substance, which implies that positive test results can be revealed moments after its last use. 

Knowing this, you must remember that varying drugs have different windows of detection in the blood [2].

The length of time that drugs remain detectable in the bloodstream is known as a detection window, and some common examples include the following:

  • Alcohol: 10-12 hours in the blood
  • Amphetamines: 12 hours in the blood
  • Barbiturates: 1-2 days in the blood
  • Benzodiazepines: 2-3 days in the blood
  • Cannabis: 2 weeks in the blood
  • Cocaine: 1-2 days in the blood
  • Codeine: Up to 12 hours in the blood
  • Heroin: Up to 12 hours in the blood
  • LSD: Up to 2-3 hours in the blood
  • MDMA: 1-2 days in the blood
  • Methamphetamine (crystal meth): 24 – 72 hours in the blood
  • Methadone: 24-36 hours in the blood
  • Morphine: 6-8 hours in the blood

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Factors That Affect Drug Detection Times In Blood

A top view of a person holding a large amount of drugsMultiple factors could influence how long drugs remain detectable in a person’s bloodstream.

The quantity of a particular drug you take can influence how much time the substance will be visible in your bloodstream during the time of drug testing.

Drugs may metabolize at varied rates, with some having rapid half-lives, allowing them to be expelled from one’s body quickly.

Administering a blood test shortly after drug usage is necessary to detect its presence.

However, individual biological factors can influence the length of time that a drug stays detectable in one’s system.

These biological factors can include:

  • Metabolism
  • Age
  • Body mass
  • Hydration levels
  • Presence of other stimulants in a sample
  • Frequency of substance abuse

“Many drugs are metabolized and excreted into the urine along with the parent drug. Both the parent drug and metabolites may be psychoactive/addictive and, thus, essential to detect. ”
Substance Abuse & Mental Health Services Administration 

Blood vs Urine Tests: What’s the Difference?

Blood and urine tests for drugs have key differences in terms of detection windows, invasiveness, and substances they can detect:

Detection Window

  • Urine Tests: Typically have a longer detection window. They can detect most drugs for several days after use, and some substances can be detected even after a week or more, especially in frequent users.
  • Blood Tests: Generally have a shorter detection window. Drugs are usually detectable in blood for only a few hours to a couple of days after use.


  • Urine Tests: Less invasive, requiring a urine sample.
  • Blood Tests: More invasive, requiring a blood draw.

Substances Detected

Both tests can detect a wide range of substances, including alcohol, amphetamines, benzodiazepines, cannabis, cocaine, opioids, and more. However, the sensitivity and specificity can vary between the two methods.


  • Blood Tests: Often considered more accurate for determining the current influence of drugs (e.g., in cases of driving under the influence).
  • Urine Tests: More commonly used for detecting past drug use rather than current intoxication.


  • Urine Tests: More commonly used in employment, legal, and medical settings due to their non-invasiveness and longer detection window.
  • Blood Tests: Often used in medical emergencies, DUI cases, and for more accurate, current-use detection.


Why Do Blood Tests Detect Addictive Substances?

Blood tests detect addictive substances in the bloodstream due to the presence of metabolites, which are chemical byproducts of drugs. Once a drug enters the human body, it is broken down into smaller particles and absorbed into different body parts. These metabolites can then be detected in blood tests for up to a certain period.

What Drugs Affect Blood Tests?

Drugs that affect blood tests include prescription drugs, cocaine, alcohol, marijuana, and heroin.

What Tests Detect Drugs In The Body?

Tests that detect drugs in the body are urine drug tests, saliva/oral fluid drug tests, hair drug tests, and sweat chromatography.

What Drugs Don’t Show Up In A Blood Test?

Drugs that don’t show up in a blood test are LSD, MDMA (ecstasy), and mushrooms. Some prescription drugs may not be detected in a standard blood drug test. It is important to remember that even though these drugs may not appear on a routine blood drug test, they can still be detected through other tests such as urine tests or hair follicle testing.

Are You Worried About Your Blood Test?

If you are worried about your upcoming drug testing procedure, the best thing to do is prepare for it. Make sure you are well-hydrated to speed up the detoxification process and reduce the amount of time drugs will be detectable in your bloodstream. 

It would help to abstain from drug use before taking blood drug tests to ensure accuracy. Additionally, you should check out Clear Choice Rescue Cleanse.

Rescue Cleanse formula is exceptionally effective in flushing out toxins from your body. It contains powerful ingredients that act as antioxidants, making it easier for your liver to filter and dispose of free radicals in the bloodstream. 



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