A toxicology report is a document that lists the drugs, chemicals, or other substances found in a person’s body, along with the amount of each substance detected. These reports are used in a wide range of situations, from emergency rooms diagnosing an overdose to forensic investigators determining a cause of death to employers screening job candidates for drug use. The specific substances tested for and the level of detail in the report depend on why it was ordered.
What a Toxicology Report Contains
At its core, a toxicology report identifies what substances are present in a biological sample and how much of each substance was found. A typical report lists each detected drug by name, the concentration measured in the sample (usually in nanograms per milliliter or milligrams per liter), and often a reference range showing what would be considered a normal therapeutic level for that substance. Some reports also include a toxicologist’s interpretation of whether the levels detected fall within a therapeutic, toxic, or potentially lethal range.
The substances covered in a standard toxicology screen are broad. According to UCSF Health, a typical panel can detect alcohol, amphetamines, antidepressants, barbiturates, benzodiazepines, cocaine, marijuana, narcotics like opioids, non-narcotic pain medicines (including acetaminophen and anti-inflammatory drugs), PCP, GHB, and prescription medications of various types. Specialized panels can be tailored to look for specific poisons, heavy metals, or less common drugs depending on the situation.
Clinical vs. Forensic Reports
There are two broad categories of toxicology reports, and they serve very different purposes. Clinical toxicology reports are generated in medical settings, typically when a patient arrives at an emergency department with suspected poisoning or overdose. The goal is speed: doctors need to know quickly what’s in the patient’s system so they can treat it. These reports prioritize fast turnaround over the level of precision that would hold up in court.
Forensic toxicology reports, by contrast, are designed to produce results that can serve as legal evidence. The University of North Carolina School of Government defines forensic toxicology as the application of toxicology to cases “where those adverse effects have administrative or medicolegal consequences, and where the results are likely to be used in court.” This means stricter chain-of-custody procedures, more rigorous testing methods, and detailed documentation at every step. Forensic reports are common in death investigations, DUI cases, workplace drug testing, and criminal prosecutions.
How Testing Works: Screening and Confirmation
Toxicology testing almost always follows a two-step process. The first step is a screening test, which is fast, inexpensive, and designed to cast a wide net. Most screening tests use a method called immunoassay, which relies on antibodies that react to certain drug classes. These tests are good at sorting samples into “possibly positive” and “negative” categories, but they aren’t precise enough to stand on their own.
That’s because immunoassay screens have a well-documented problem with false positives. A review in the Journal of Analytical Toxicology found a long list of common medications that can trigger incorrect results. The diabetes drug metformin and the antidepressant bupropion can cause false positives for amphetamines. The antipsychotic quetiapine can mimic tricyclic antidepressants. The HIV medication efavirenz can falsely flag for both marijuana and benzodiazepines. Even over-the-counter painkillers like ibuprofen and naproxen have been linked to false-positive barbiturate results.
Because of these limitations, any positive screening result gets sent for confirmatory testing. This second step uses more sophisticated technology, often mass spectrometry, which can identify the exact molecular structure of a substance and measure its precise concentration. Confirmatory results are far more specific and reliable, and they’re the ones that appear on a final toxicology report. Immunoassay results alone cannot be used as evidence in court.
Types of Samples Collected
Blood and urine are the most common specimens, but a toxicology report can be based on several different sample types, each with its own strengths.
- Blood (or serum/plasma): Provides the best snapshot of what’s actively circulating in the body at the time of collection. It’s the gold standard for measuring current impairment or therapeutic drug levels.
- Urine: Detects substances over a longer window than blood, making it the preferred specimen for workplace drug testing and many forensic screens. Detection windows vary widely by substance.
- Hair: Can reveal drug use patterns over weeks or months, since substances are incorporated into hair as it grows.
- Oral fluid (saliva): Increasingly used in workplace testing. The U.S. Department of Transportation authorized oral fluid testing for federally regulated employees in June 2023.
- Vitreous humor: The gel-like fluid inside the eye, used exclusively in post-mortem investigations. Because it’s isolated from the rest of the body behind the blood-retinal barrier, it resists bacterial contamination and degrades much more slowly than blood after death. This makes it especially valuable when a body isn’t discovered quickly.
How Long Substances Stay Detectable
One of the most important things to understand about a toxicology report is that detection windows vary enormously depending on the substance, the type of sample, and individual factors like metabolism and frequency of use. In urine, cocaine is typically detectable for only one to two days, while marijuana can show up anywhere from one to 45 days depending on how often a person uses it. Fentanyl has a urine window of one to seven days. Common benzodiazepines range from one to two days for short-acting types up to 20 days for certain long-acting forms.
Some other common urine detection windows: amphetamines one to seven days, opioids like oxycodone and morphine one to three days, methadone one to 14 days, and alcohol (measured through its metabolic byproducts) one to four days. These are estimates. Body weight, hydration, liver function, age, and chronic versus single use all shift these timelines. A negative result doesn’t necessarily mean a substance was never used; it may simply mean it was used outside the detection window.
Workplace Drug Testing Reports
Workplace toxicology reports follow their own set of rules, particularly for employees in safety-sensitive positions regulated by the Department of Transportation. DOT testing covers workers in aviation, trucking, railroads, public transit, pipelines, and maritime industries.
The process is tightly controlled. Every DOT test requires a Federal Drug Testing Custody and Control Form. Specimens are collected as two separate bottles: Bottle A is tested, while Bottle B is stored as a backup that the employee can request be tested at a different lab if they dispute the result. Collection sites follow strict security protocols, including turning off water sources, adding blue dye to toilet water, removing soap and cleaning products, and inspecting the area for hidden contaminants. For oral fluid collections, the entire process is conducted under direct observation.
Once the lab produces results, they go to a Medical Review Officer, a licensed physician who reviews positive results before they’re reported to the employer. This step exists specifically to catch false positives from legitimate prescriptions or other explainable causes.
Post-Mortem Toxicology Reports
When someone dies and the cause isn’t immediately clear, a forensic toxicology report is often a central part of the death investigation. Coroners and medical examiners order these reports to determine whether drugs, alcohol, or poisons contributed to the death.
Post-mortem testing comes with unique challenges that don’t exist in living patients. After death, drugs can redistribute throughout the body as cells break down, sometimes making blood concentrations unreliable. This is one reason forensic pathologists collect samples from multiple sites, including blood from different locations in the body, urine, bile, liver tissue, and vitreous humor from the eyes. The vitreous is particularly useful because its isolation from the bloodstream means it better reflects the drug levels that were present before death.
A post-mortem toxicology report will typically note that its reference ranges were established in living subjects and may not directly apply. Interpreting these results requires expertise, as the same blood concentration of a drug can mean very different things in a living person versus someone whose body has been undergoing decomposition.
How Long Results Take
Turnaround time depends heavily on the type of report. A basic emergency room drug screen can produce preliminary results in minutes to hours. Workplace drug tests typically come back within a few business days. Forensic toxicology reports, particularly in death investigations, take much longer. Weeks to several months is common, because forensic labs often test for a wider range of substances, run more confirmatory tests, and face significant backlogs. Complex cases requiring specialized testing for unusual poisons or novel synthetic drugs can take even longer.