Why 'none detected' does not mean none
Two abbreviations on a laboratory report are routinely read as zero, and neither means zero. They mean that a method could not produce a reliable number at a stated threshold, which is a claim about the instrument rather than about the sample.
The distinction is not academic. It decides whether a product can be described as free of a substance, whether a compliance figure is meaningful, and whether two reports from different laboratories can be compared at all.
This page explains what the thresholds are, how they are established, why they differ between laboratories, what an absent number legitimately supports and what it does not, and how to read a report where several lines carry them.
⚠️ Scope. This page describes a process and what can be verified from documents. It does not describe what a product does to a person, gives no amounts, and does not replace a healthcare professional.
🔴 The two thresholds
Limit of detection
The lowest concentration at which the method can reliably tell that something is present. It can distinguish signal from noise, but not measure how much.
Limit of quantification
The lowest concentration at which the method can produce a number with acceptable reliability. It is always higher than the detection limit.
The gap between them
Between the two, a substance is detectable but not measurable. Reports handle this zone in different ways and the notation varies.
Which one appears on reports
Usually quantification, because that is what a numerical result requires. Detection appears more often on contaminant panels.
The notations used
LOQ or LQ
Below the limit of quantification. The most common notation on cannabinoid panels.
ND
Not detected. Strictly this means below the detection limit, which is a stronger statement than below quantification.
The less-than symbol
A figure preceded by a less-than sign, such as a value below a stated threshold. This is the clearest notation because it names the threshold.
Blank cells
Some reports simply leave a cell empty. This is ambiguous and should be read as an absence of information rather than an absence of substance.
What sets the threshold
The method
Liquid chromatography, gas chromatography and mass spectrometry all have different sensitivities. The threshold follows from the technique.
The instrument
Two laboratories running the same technique on different equipment reach different thresholds. Newer instruments generally go lower.
The matrix
Extracting a compound from an oil is harder than from a solvent. The surrounding material affects how low a method can reliably reach.
The dilution
Sample preparation dilutes the material, and the threshold scales with it. A heavily diluted sample has a proportionally higher effective threshold.
Why thresholds differ between reports
Nothing standardises them
Laboratories set them according to their validation work. Two accredited laboratories can legitimately report different thresholds for the same analyte.
The consequence for comparison
A result reported as below threshold at one laboratory might be a measurable number at another. Neither is wrong.
What accreditation covers
ISO/IEC 17025 accreditation attests competence for a stated method, including its validated thresholds. It does not impose a common value.
How to handle it
Read the threshold before reading the result. A report that does not state its thresholds cannot be compared to one that does.
🔴 What an absent number supports
A bounded statement
That the concentration is below a stated figure. This is genuine information and it is often sufficient.
What it does not support
That the substance is absent. No analytical method demonstrates absence; methods demonstrate that something is below a threshold.
The commercial temptation
Describing a product as free of a substance on the basis of a below-threshold result. The claim goes beyond what the measurement shows.
The defensible phrasing
Below the limit of quantification of the stated method, with the threshold given. Longer, accurate, and it survives scrutiny.
The compliance case
Where it bites
Regulatory limits on total THC are expressed as concentrations. A result below threshold is compliant, but the margin is unknown.
The calculation problem
Total THC requires delta-9-THC plus THCA multiplied by 0.877. If one term is below threshold, the sum carries that uncertainty.
The conservative reading
Entering a below-threshold value as equal to the threshold gives a worst-case total. Some producers report it this way and it is the honest approach.
Why this matters at borders
Enforcement uses the measured figure. A worst-case calculation that stays under the limit is a stronger position than one that assumes zero.
Contaminant panels
The stakes
Pesticides, heavy metals and residual solvents are screened against maximum levels. Below-threshold results are the expected outcome.
What the threshold must be
Meaningfully below the regulatory limit. A method whose threshold sits above the permitted maximum cannot demonstrate compliance at all.
The check to make
Compare the stated threshold against the applicable limit. If the threshold is higher, the pass result is empty.
How often this is checkable
Rarely, because most reports omit thresholds on contaminant panels. Their inclusion is a marker of a thorough report.
The concentrate multiplier
The arithmetic
Extraction concentrates everything present in the starting material, including substances that were below threshold in the flower.
What follows
A contaminant undetectable in raw material can become measurable in an extract made from it. The absence of a number upstream does not carry downstream.
The correct approach
Test the finished product, not the input. A report on the starting material does not describe the extract.
Where this matters most
On solvent extractions, where both the concentration factor and the residual solvent question apply to the same product.
Minor cannabinoids
The usual picture
CBG, CBN, CBC and their acid forms frequently appear below threshold on flower panels. This is normal and expected.
What a measurable CBN means
That oxidative degradation has progressed. On a fresh, compliant flower the figure is often below threshold precisely because there was little to degrade.
The marketing use
Products sold on the presence of a minor cannabinoid should show a measured figure, not a below-threshold notation.
The question to ask
What is the measured content of the compound the product is named after. If the answer is below threshold, the naming is doing work the analysis does not support.
Reading a report with several below-threshold lines
The first question
Is the threshold stated. Without it, the notation conveys nothing beyond the fact that a test was run.
The second
Is the threshold appropriate to the question. A high threshold makes a pass easy and uninformative.
The third
Which lines carry numbers. A report where the compounds of interest are quantified and the contaminants are below threshold is the expected shape.
The pattern that concerns
Below-threshold notations on the compounds being sold, and numbers only on the contaminants. That inverts the useful arrangement.
Method validation in brief
What it establishes
That a method produces reliable results across a stated range, with known precision and known thresholds. It is done once and reviewed periodically.
The parameters
Linearity, accuracy, precision, specificity, and the detection and quantification limits. All are part of the validation record.
Why it matters to a buyer
A validated threshold is a defensible number. An unvalidated one is an estimate, and reports rarely distinguish between the two.
Where to find it
In the method section of a full report, or on request from the laboratory. Most published reports show only a summary.
The arithmetic of uncertainty
Measurement uncertainty
Every result carries a range, expressed as a percentage or an interval. Accredited reports state it; summaries usually omit it.
What it means for comparison
Two results whose ranges overlap are not distinguishable. A difference of a few per cent relative is frequently within uncertainty.
The practical rule
Small differences between batches are noise. Differences of tens of per cent are signal.
Why it is rarely shown
It complicates a document meant to reassure. Its presence is a marker of a report written for technical readers.
What the notation costs sellers
The easy path
Reporting a below-threshold result as zero, or as free of. It reads better and the distinction is invisible to most buyers.
The regulatory exposure
A claim of absence that a method cannot support is a claim about a characteristic of the product. That places it within the scope of information rules.
The honest alternative
Stating the threshold alongside the result. It is one extra line and it removes the exposure entirely.
The signal for a buyer
A seller who reports thresholds is telling you they expect the document to be read by someone who knows what they mean.
Independent verification
When it is worth doing
Where a declared content is materially in question, or where a below-threshold claim of absence underpins the purchase decision.
What it costs
A single-panel analysis at a commercial laboratory is affordable relative to a large purchase. Full panels cost considerably more.
Choosing a laboratory
Accredited to ISO/IEC 17025 for the relevant method, and willing to state its thresholds. Both should be confirmed before submitting.
What the result supports
A comparison against the seller’s report. Where the two disagree beyond uncertainty, the file is complete enough for a conformity complaint.
Common misreadings
Zero on a chart
Report software sometimes plots below-threshold values as zero. The chart is a rendering, the table is the data.
Comparing across laboratories
Different thresholds make below-threshold notations non-comparable. Only stated numbers compare.
Reading ND as stronger everywhere
Some laboratories use ND for below quantification rather than below detection. Read the legend.
Assuming a low threshold
Thresholds vary by more than an order of magnitude between panels and laboratories. Never assume.
What a good report does
States thresholds
For every analyte, or at minimum for every panel. This is the single most useful addition a laboratory can make.
Distinguishes the notations
A legend explaining what LOQ, LOD and ND mean in that document. Uncommon and immediately clarifying.
Reports uncertainty
At least for the primary analytes. It converts a point figure into a range, which is what it actually is.
Names the method
So that a reader can judge whether the thresholds are appropriate for the question being asked.
How a threshold is actually determined
The signal-to-noise approach
The instrument produces a baseline of background signal. Detection is conventionally set where the analyte signal reaches roughly three times that noise, and quantification at around ten times.
The calibration approach
A series of standards at known concentrations is run, and the threshold is derived from the scatter of the resulting calibration line at its lower end. This is the more rigorous of the two.
Why the method chosen matters
The two approaches do not always give the same figure. A report that states which was used is telling its reader something about the care behind the number.
What changes over time
Instruments drift, columns age, and thresholds move with them. Validation is periodically repeated, which is one of the things accreditation actually audits.
The dilution factor in practice
What happens to a sample
A concentrated extract cannot be injected undiluted without overloading the instrument. It is diluted, sometimes by a factor of hundreds, before analysis.
The consequence for thresholds
The effective threshold on the original material is the instrument threshold multiplied by the dilution factor. A very low instrument threshold can become a mediocre one on the product.
Why this is invisible
Reports state the result on the product, not the dilution applied. The relationship between the two sits in the working record rather than the summary.
The question that surfaces it
Ask what dilution was used and what the instrument threshold was. A laboratory answers this readily; a reseller passing on a document usually cannot.
Reporting conventions that mislead
Rounding to zero
A value below threshold entered into a spreadsheet as zero, then summed with others. The total is then arithmetically wrong in a direction that flatters.
Percentage displays
Small values rendered as 0.00% by a two-decimal display. The underlying figure may be an order of magnitude above zero.
Summed totals
A total-cannabinoid figure computed by entering below-threshold results as zero. The convention should be stated and almost never is.
What a careful report does
Keeps below-threshold entries as notations rather than numbers, and excludes them from sums with an explicit footnote.
The regulatory reading
How enforcement reads it
Authorities work from the measured figure and the method behind it. A below-threshold result on an appropriate method supports compliance; on an inappropriate one it does not.
The burden of the operator
Food law places responsibility on the operator to ensure that what they place on the market meets the applicable requirements. A weak analytical threshold does not discharge that.
Where limits are set
Maximum levels for contaminants in food and criteria for residual solvents are established in published Union instruments and technical guidance. The thresholds of a method have to sit meaningfully below them.
The practical upshot
An operator relying on a below-threshold result should be able to state the threshold. If they cannot, the compliance position rests on a figure nobody has looked at.
What the buyer can reasonably conclude
From a stated threshold
That the content is below a known figure. Combined with the applicable limit, this is often a complete answer.
From an unstated one
Very little. The notation records that a test was run, and nothing about how sensitive it was.
From a pattern across a report
A document that states thresholds throughout was written to be checked. One that omits them throughout was written to be shown.
From the seller’s answer
The response to a question about thresholds separates the operations that understand their own documents from those that forward them.
Where the threshold question ends
The honest summary
A laboratory can say what a substance is below. It cannot say that a substance is absent, and no instrument ever built has been able to. Every claim of absence is really a claim about a threshold, with the threshold left out.
What that leaves a buyer
A bounded statement, which is genuinely useful once the bound is known. The whole difficulty is that the bound is the part most often omitted from the document a buyer is shown.
A short glossary
Limit of detection
The lowest concentration at which a method can reliably establish that a substance is present, without measuring how much.
Limit of quantification
The lowest concentration at which a method can produce a numerical result of acceptable reliability. Always higher than the detection limit.
Matrix
The material surrounding the analyte. It affects how low a method can reliably measure.
Measurement uncertainty
The range within which the true value is expected to lie, reported alongside an accredited result.
Method validation
The documented process establishing that an analytical method performs reliably across a stated range, including its thresholds.
The five checks that apply to any product
The batch certificate
Request it with the number printed on the packaging. A general document for the product line does not cover this batch, and those differences are exactly what it should record.
Total THC
Delta-9-THC plus THCA multiplied by 0.877, because THCA becomes THC under heat and the limit applies to the sum, not to either value alone.
Price per milligram
A division, not an opinion. The only figure that makes two products comparable, whatever the format, process and pack size.
The claims
Without an authorisation number in the EU Register these are assertions, not data — and for cannabidiol that register contains no authorised entry to this day.
The seller’s details
Company name, address and contact. Without them there is also no counterparty to turn to if something turns out to be wrong.
How this connects to the rest
With reading a certificate
Thresholds determine what the rest of the document means. They belong in the first pass, not the last.
With total THC
A below-threshold term in the calculation carries uncertainty into the sum. The conservative reading is the defensible one.
With concentrates
Concentration factors turn below-threshold results in raw material into measurable ones in the finished product.
With claims
Absence cannot be demonstrated analytically. Any claim of freedom from a substance goes beyond what the method supports.
What this is for in practice
When reading a report
Find the thresholds before reading the results. Their presence or absence sets what the document is worth.
When a claim says free of
Ask for the threshold and the method. A specific answer settles it; a vague one settles it differently.
When comparing two reports
Only quantified numbers compare. Below-threshold notations from different laboratories do not.
When a minor compound is the selling point
Ask for its measured content. A below-threshold notation on the compound in the product name is the answer.
Frequently asked questions
What does LOQ mean? Below the limit of quantification: the method cannot produce a reliable number at that threshold. It does not mean zero.
What is the difference between LOD and LOQ? Detection establishes presence, quantification produces a number. The quantification threshold is always higher.
Does ND mean the substance is absent? No. It means below the detection threshold of that method. Absence cannot be demonstrated analytically.
Why do thresholds differ between laboratories? They follow from the method, the instrument, the matrix and the dilution. Nothing standardises them across laboratories.
How does this affect total THC? If one term of the calculation is below threshold, the sum inherits that uncertainty. The conservative approach uses the threshold value.
Can a product be called free of a substance? Not on the basis of a below-threshold result. The defensible phrasing states the threshold and the method.
Does a contaminant pass always mean compliance? Only if the method threshold is meaningfully below the regulatory limit. A threshold above the limit makes the pass empty.
Why do minor cannabinoids show as below threshold? Because they are frequently present in very small amounts. On a compliant flower this is the expected result.
What is measurement uncertainty? The range within which the true value is expected to lie. Accredited reports state it; summaries often omit it.
Should I get an independent test? Where a declared content is materially in question, and where the purchase is large enough to justify the cost.
What we check and what we do not
We check what can be checked from documents: official registers, declared contents, certificates of analysis, arithmetic. We test no products, rank nothing, and assert no effects.
This is the point in a report where a technical statement becomes a commercial one without anyone changing a word. A laboratory writes that it could not measure below a threshold; a product page reads that as none present; a buyer reads that as a guarantee. Each step is small and the end result is not what the instrument said.
The correction is equally small. Find the threshold, read the notation against it, and take a below-threshold result as the bounded statement it is. It takes seconds and it is the difference between reading a document and being reassured by one.