THC & Testing Glossary

This focused thc testing glossary explains the lab terms you’ll see on Certificates of Analysis (COAs) and in product testing reports—especially those relevant to choosing and verifying THC-free CBD products. It is designed to help you read labels, interpret results, and understand how “non-detect” is determined.

Because THC testing intersects with drug-testing policies and analytical chemistry, definitions below use cautious, plain language. Always refer to the original lab report for exact methods, units, and detection limits.

For broader terminology and in-depth topic overviews, please visit our Glossary & Learning Center. For terminology specific to lab reports, see the COA Glossary. For plant compounds, see the Cannabinoid Glossary and Terpene Glossary.

Disclaimer: This page is informational only and not legal, medical, or testing advice. Drug-testing policies, lab practices, and regulations vary by jurisdiction and program.

Key THC concepts

THC (tetrahydrocannabinol): A family of related compounds; when people say “THC,” they usually mean delta-9-THC, the primary intoxicating cannabinoid historically linked to cannabis.
Δ9-THC (delta-9-THC): The form commonly regulated and measured for compliance and drug-testing concerns. Reported on COAs as “Delta-9 THC” or similar.
THCA (tetrahydrocannabinolic acid): The non-intoxicating acidic precursor to delta-9-THC. Heat or time can convert THCA to delta-9-THC (decarboxylation).
Decarboxylation: The process that converts acidic cannabinoids (like THCA) into their neutral forms (like delta-9-THC). Happens with heat (e.g., vaping, baking) or slowly over time.
Total THC: A calculated value used in compliance contexts. Common formula: Total THC = Δ9-THC + (THCA × 0.877). The factor 0.877 adjusts for the CO₂ mass lost when THCA converts to Δ9-THC.
THC-free: In lab reporting, this typically means THC is “non-detect” at the laboratory’s LOQ (limit of quantitation). It does not necessarily mean absolute zero molecules; it means any THC is below the lab’s reliable quantitation threshold.

Lab testing essentials

Certificate of Analysis (COA): A third-party lab report documenting what was tested, the methods used, results, units, LOQ/LOD, and lab accreditation. See our COA Glossary for COA-specific fields and sections.
Method (HPLC, GC-MS, LC-MS/MS): Analytical techniques used to measure cannabinoids. HPLC is common for potency without decarboxylating the sample. GC-based methods may convert acidic forms unless derivatized.
LOD (Limit of Detection): The smallest amount that can be distinguished from zero (signal is detectable) but may not be measured with reliable precision.
LOQ (Limit of Quantitation): The lowest level that can be measured with acceptable accuracy and precision. Results below LOQ are often reported as “< LOQ.” This loq lod glossary distinction matters when interpreting “non-detect.”
Non-detect (ND): Indicates the analyte was not detected or not quantifiable under the method’s conditions. ND does not prove absolute absence; it reflects the test’s sensitivity.
Measurement uncertainty (MU): A statistical range around the reported value. Good labs state MU to reflect variability inherent in measurement.
Matrix: The sample type tested (e.g., oil, gummy, tincture). Matrix can influence recovery, LOQ, and result reliability.
Batch/Lot: The specific production run tested. Matching your product’s lot number to the COA helps ensure the results apply to what you have.
Chain of custody: Documentation tracking a sample from collection to analysis to maintain integrity and traceability.

Units and reporting

% (percent): Often w/w (weight/weight) for solids or viscous oils, or w/v (weight/volume) for liquids. 1.0% w/w = 10 mg/g.
mg/g and mg/mL: Mass of analyte per gram or per milliliter of product. Useful for calculating mg per serving from potency per unit mass or volume.
PPM (parts per million): ppm THC definition: 1 ppm ≈ 1 mg/kg (solids) or 1 mg/L (water-like liquids). 10 ppm = 0.001%. PPB = parts per billion (1 µg/kg).
ng/mL: Nanograms per milliliter. Common unit in urine drug testing (e.g., screening cutoff 50 ng/mL for THC metabolite in many workplace programs).
Dry weight vs. “as formulated”: Dry weight normalizes moisture differences (common in raw hemp). Finished products (oils, gummies) are typically reported “as is.”
Serving-level math: mg per serving = (potency per unit) × (serving size). Example: 0.10% THC = 1 mg/g. A 2 g serving would contain ~2 mg if present at that level.

Drug testing basics (THC awareness)

What tests measure: Most workplace urine tests target the metabolite THC-COOH, not CBD.
Typical federal workplace cutoffs (urine): Initial immunoassay screen at 50 ng/mL THC-COOH; confirmatory GC/MS or LC-MS/MS at 15 ng/mL. Programs and jurisdictions may differ.
Variability: Detection windows vary widely based on use patterns, individual factors, product composition, and test sensitivity.
Risk perspective for THC-free users: Products tested as “ND at LOQ” reduce—but cannot guarantee eliminating—risk of a positive THC result. Verify up-to-date COAs, methods, and LOQs for the specific lot you use.

Reading THC on a COA

Confirm the sample identity (product name and lot) matches what you have.
Find the cannabinoid potency table. Note Δ9-THC, THCA, and the reported “Total THC.”
Check units (%, mg/g, mg/mL) and the method used (e.g., HPLC).
Locate LOQ/LOD and any footnotes. “ND” or “< LOQ” indicates levels below the lab’s quantitation limit.
Review measurement uncertainty and lab accreditation to gauge result quality.

Looking for products tested to be THC-free? Explore options at cannagea.com/thc-free.

FAQ

Does “THC-free” mean zero THC?

Not necessarily. It typically means THC was non-detect at the lab’s LOQ. Always check the COA for the LOQ value and method.

What ppm of THC counts as non-detect?

There isn’t a universal ppm threshold. “ND” depends on the lab and method. The COA should list the LOQ (often in ppm, mg/g, or %). If the result is “< LOQ,” it’s considered non-detect relative to that test.

What’s the difference between LOD and LOQ?

LOD is the smallest amount distinguishable from zero; LOQ is the lowest amount that can be measured with acceptable accuracy and precision. LOQ is higher than LOD.

What are common workplace urine cutoffs for THC?

Many programs use a 50 ng/mL immunoassay screen and a 15 ng/mL confirmatory test for THC-COOH. Policies vary; always consult the applicable program documentation.

How do I estimate mg of THC per serving?

Convert the potency unit to mg per gram or mL, then multiply by serving size. Example: 0.005% THC = 0.05 mg/g; a 5 g serving would contain ~0.25 mg if present at that level.

Summary

This page clarifies how THC, THCA, Total THC, LOD/LOQ, and reporting units work together on lab reports. For THC-free users, “non-detect” reflects a lab’s quantitation threshold—not absolute zero—so always confirm methods, LOQs, units, and lot numbers on the COA. For broader context, explore our Glossary & Learning Center and the dedicated COA Glossary, Cannabinoid Glossary, and Terpene Glossary.