Exploro Information Hub
Drug Testing Information Hub
Clear answers about drug tests, workplace rules, results and what happens next — explained using official government and scientific sources.
Why are you looking into drug testing?
Pick the situation closest to yours. Each route starts with the question people in that situation ask first.
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Pre-employment test
I have a test coming up for a new job.
11 guides → -
DOT-regulated job
My job is regulated by the U.S. Department of Transportation.
21 guides → -
Random testing
My employer can test me without warning.
6 guides → -
Positive result
My test came back positive and I need to know what happens now.
16 guides → -
At-home test
I bought a test to use at home and want to read it correctly.
11 guides → -
Drug-test laws
I want to know what my state and my employer are allowed to do.
Coming soon -
Employer / HR
I run testing for a team and need the rules straight.
8 guides → -
Another reason
I am testing for a personal or family reason.
2 guides →
Start with your situation
Pre-employment test
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Drug Testing 101
What Is Chain of Custody in Drug Testing?
What is chain of custody in drug testing?
Read the answer → -
What Happens Next
What Happens if You Fail a Pre-Employment Drug Test?
What happens if you fail a pre-employment drug test?
Read the answer → -
Results & Interpretation
What Can Cause a False Positive Drug Test?
What can cause a false positive drug test?
Read the answer → -
Drug Testing 101
How Does Drug Testing Work?
How does drug testing work?
Read the answer → -
Workplace Testing
Pre-Employment Drug Testing: What to Expect
What should I expect from a pre-employment drug test?
Read the answer →
DOT-regulated job
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Drug Testing 101
What Is Chain of Custody in Drug Testing?
What is chain of custody in drug testing?
Read the answer → -
DOT & Federal Testing
DOT Drug-Test Panel and Cutoffs (49 CFR §40.85)
What are the DOT drug test cutoff levels?
Read the answer → -
DOT & Federal Testing
DOT Drug Testing: The Complete Employee Guide
What is DOT drug testing and how does it work?
Read the answer → -
DOT & Federal Testing
The DOT Return-to-Duty Process, Step by Step
How does the DOT return-to-duty process work?
Read the answer → -
Drug Testing 101
What Is a Drug-Test Cutoff?
What is a drug-test cutoff?
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Random testing
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DOT & Federal Testing
DOT Drug Testing: The Complete Employee Guide
What is DOT drug testing and how does it work?
Read the answer → -
Workplace Testing
How Random Drug Testing Works
How does random drug testing work?
Read the answer → -
Workplace Testing
Reasonable Suspicion Drug Testing: What It Requires
What counts as reasonable suspicion for a drug test?
Read the answer → -
Rights & Special Situations
What Counts as Refusing a Drug Test?
What counts as refusing a drug test?
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Testing Methods
How Urine Drug Testing Works
How does a urine drug test work?
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Positive result
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Drug Testing 101
What Is Chain of Custody in Drug Testing?
What is chain of custody in drug testing?
Read the answer → -
DOT & Federal Testing
DOT Drug-Test Panel and Cutoffs (49 CFR §40.85)
What are the DOT drug test cutoff levels?
Read the answer → -
DOT & Federal Testing
The DOT Return-to-Duty Process, Step by Step
How does the DOT return-to-duty process work?
Read the answer → -
Drug Testing 101
What Is a Drug-Test Cutoff?
What is a drug-test cutoff?
Read the answer → -
What Happens Next
What Happens if You Fail a Pre-Employment Drug Test?
What happens if you fail a pre-employment drug test?
Read the answer →
At-home test
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Drug Testing 101
What Is a Drug-Test Cutoff?
What is a drug-test cutoff?
Read the answer → -
Results & Interpretation
What Can Cause a False Positive Drug Test?
What can cause a false positive drug test?
Read the answer → -
Drug Testing 101
How Does Drug Testing Work?
How does drug testing work?
Read the answer → -
Results & Interpretation
How to Read a Home Drug Test
How do you read a home drug test?
Read the answer → -
Results & Interpretation
Negative, Dilute, and Invalid Results Explained
What does a dilute or invalid drug test result mean?
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Employer / HR
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DOT & Federal Testing
Post-Accident Drug Testing: When It Is Required
When is post-accident drug testing required?
Read the answer → -
Workplace Testing
Pre-Employment Drug Testing: What to Expect
What should I expect from a pre-employment drug test?
Read the answer → -
Workplace Testing
How Random Drug Testing Works
How does random drug testing work?
Read the answer → -
Workplace Testing
Reasonable Suspicion Drug Testing: What It Requires
What counts as reasonable suspicion for a drug test?
Read the answer → -
Rights & Special Situations
What Counts as Refusing a Drug Test?
What counts as refusing a drug test?
Read the answer →
Another reason
In research and not yet published: Drug-test laws. A guide goes live only once every source behind it has been opened and checked.
All guides by topic
Drug Testing 101
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Drug Testing 101
What Is Chain of Custody in Drug Testing?
What is chain of custody in drug testing?
Read the answer → -
Drug Testing 101
What Is a Drug-Test Cutoff?
What is a drug-test cutoff?
Read the answer → -
Drug Testing 101
How Does Drug Testing Work?
How does drug testing work?
Read the answer → -
Drug Testing 101
What Is a Medical Review Officer (MRO)?
What is a Medical Review Officer?
Read the answer → -
Drug Testing 101
Screening vs. Confirmation: Why Drug Tests Have Two Steps
Why do drug tests have two steps?
Read the answer → -
Drug Testing 101
What Is a Drug Test?
What is a drug test?
Read the answer →
Testing Methods
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Testing Methods
How Saliva (Oral-Fluid) Drug Testing Works
How does a saliva drug test work?
Read the answer → -
Testing Methods
How Urine Drug Testing Works
How does a urine drug test work?
Read the answer → -
Testing Methods
Urine vs. Saliva vs. Hair Drug Tests Compared
What is the difference between urine, saliva and hair drug tests?
Read the answer →
Substances & Analytes
Workplace Testing
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Workplace Testing
Pre-Employment Drug Testing: What to Expect
What should I expect from a pre-employment drug test?
Read the answer → -
Workplace Testing
How Random Drug Testing Works
How does random drug testing work?
Read the answer → -
Workplace Testing
Reasonable Suspicion Drug Testing: What It Requires
What counts as reasonable suspicion for a drug test?
Read the answer → -
Workplace Testing
Workplace Drug Testing: The Complete Guide
What are the rules for workplace drug testing?
Read the answer →
DOT & Federal Testing
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DOT & Federal Testing
DOT Drug-Test Panel and Cutoffs (49 CFR §40.85)
What are the DOT drug test cutoff levels?
Read the answer → -
DOT & Federal Testing
DOT Drug Testing: The Complete Employee Guide
What is DOT drug testing and how does it work?
Read the answer → -
DOT & Federal Testing
The DOT Return-to-Duty Process, Step by Step
How does the DOT return-to-duty process work?
Read the answer → -
DOT & Federal Testing
What Happens if You Fail a DOT Drug Test?
What happens if you fail a DOT drug test?
Read the answer → -
DOT & Federal Testing
Post-Accident Drug Testing: When It Is Required
When is post-accident drug testing required?
Read the answer →
Results & Interpretation
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Results & Interpretation
What Can Cause a False Positive Drug Test?
What can cause a false positive drug test?
Read the answer → -
Results & Interpretation
How to Read a Home Drug Test
How do you read a home drug test?
Read the answer → -
Results & Interpretation
Negative, Dilute, and Invalid Results Explained
What does a dilute or invalid drug test result mean?
Read the answer → -
Results & Interpretation
What Does a Preliminary Positive Mean?
What does a preliminary positive drug test mean?
Read the answer →
What Happens Next
Rights & Special Situations
In research and not yet published: Laws by State, Glossary. A guide goes live only once every source behind it has been opened and checked.
Tools
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THC Detection Calculator
Answer a few questions about frequency, body composition and last use to see an estimated detection window for a urine test.
An estimate, not a guarantee — individual results vary widely. Cutoff comparison tool
Compare the DOT panel, the HHS federal-agency panel and common at-home test levels side by side.
In development
Drug testing laws by state
Federal rules set the floor for regulated jobs. Everything else depends on your state and your employer's written policy.
State summaries are in research. A state will appear here only once its summary has been checked against that state's own statutes and agency guidance — until then we would rather point you at the official source than publish a guess.
Official sources first
Every regulatory fact here comes from the agency that writes the rule — SAMHSA, the Department of Transportation, the FDA, the eCFR — and each source is listed at the bottom of the guide with the date we checked it.
Reviewed by a certified examiner
Medical and procedural content is reviewed with Dr. Matthew Nuesse, DOT Certified Medical Examiner.
What “last verified” means
It is the date we last opened every source cited on that page and confirmed the rule still reads the same. Rules change; the date tells you how current the answer is.
