Label of dried cannabis at twenty percent: total THC, acid form, and conversion factor 0.877

• How many pieces of evidence. 4 works from 2021 to 2025, all listed in the table below along with the model.
• What has not been demonstrated. It has not been shown that a higher declared percentage on the label means stronger or better therapeutic effects. The evidence material regarding the potency of the raw material concerns almost exclusively adverse effects and non-medical use, not effectiveness.
• What you will not find here. Dosage recommendations or strain indications. The choice is made by the attending physician, and cannabis is a raw material dispensed only by prescription.
• How to read this. The result of a study on rodents or in cell culture does not directly transfer to a patient taking the dried material, and the column with the model indicates what the work was actually about.

What exactly does twenty percent on the dried cannabis label mean?

It means that the manufacturer declares twenty percent total tetrahydrocannabinol in a gram of dried raw material, and the laboratory must confirm this value by measurement. The monograph allows for a ten percent difference between the measured and declared content, so under one number lies a range from eighteen to twenty-two percent, not a point.

The declaration covers total tetrahydrocannabinol, which is the sum of the neutral form and its acid counterpart converted to THC. The same applies to cannabidiol, as the monograph requires both values at once. The measurement is performed by the laboratory using chromatographic methods on a sample taken from the batch, and the result refers to the mass of the dried raw material.

The number on the label is therefore a report of the composition measurement, not a promise of what the patient will feel. It describes one gram of the flower at the time of testing the batch. It says nothing about the dose, the route of administration, or the outcome of therapy, although in casual reading it takes on all three roles at once.

This page is not a product list and does not mention any item from the offer. What is currently in circulation and with what declaration is shown in the summary of currently available medical marijuana strains. Separately, we also explain why the ranges of neighboring declarations overlap.

What is the difference between tetrahydrocannabinol and its acid form?

They differ by one carboxyl group, and that is enough for them to be two separate compounds. In freshly harvested and dried flowers, tetrahydrocannabinol primarily occurs as tetrahydrocannabinolic acid, abbreviated as THCA. Only the removal of this group, i.e., decarboxylation, converts the molecule into THC, which is discussed in the literature regarding the effects of the raw material.

The plant does not produce the neutral form. An enzyme called tetrahydrocannabinolic acid synthase converts a common acid precursor into THCA, and it is this acid that accumulates in the glandular hairs of the flower. The neutral form is produced later, outside the plant’s metabolism, in a reaction that does not require any enzyme but does require energy.

For reading the label, this has a simple and often overlooked consequence. If the laboratory provided only THC measured in the raw dried material, the value would be many times lower than that declared by the manufacturer, as most of the material is still in the acid form. The monograph resolves this by requiring both forms to be counted together, after converting the acid to its neutral counterpart. The label thus describes the potential of the raw material, not the content of the active substance in the jar.

The result of the batch test may therefore be presented in two columns: the neutral form separately, the acid separately. Anyone reading only the first of them reads a fraction of what the raw material actually carries. Anyone summing both without conversion overestimates the result by the mass that, when heated, escapes as gas and reaches no one.

Where does the conversion factor 0.877 come from?

From the ratio of the molecular weights of both forms. Tetrahydrocannabinol has the molecular formula C21H30O2, while its acid form is C22H30O4, meaning the same molecule enlarged by a carboxyl group. During decarboxylation, carbon dioxide is released, so from one gram of acid, less than 0.88 grams of THC remains, and the rest escapes as gas.

The calculation can be performed on paper. The weights from the table give the ratio of 314.47 to 358.48, which is 0.8772, rounded in regulations to 0.877. Checking from the other side yields the same result: 358.48 minus 44.01, i.e., the weight of carbon dioxide, gives exactly 314.47. The missing 12.28 percent of the mass is the gas that escapes when heated.

This same conversion factor works in two places at once. The pharmacopoeial designation counts the content of the neutral form together with its corresponding acid, correcting the result by the ratio of molecular weights. American cannabis regulations state this directly as the sum: THC content increased by 0.877 of the THCA content. The molecular formulas of both compounds are provided by the public database PubChem, maintained by the National Center for Biotechnology Information.

Two things can easily be confused here. The factor 0.877 is a ratio of molecular weights, not a measure of how efficiently the conversion occurs outside the laboratory. It indicates how much THC would be produced from the acid in a complete conversion, not how much is produced in the patient’s device or how much remains after six months in the jar. The declaration on the label is calculated using the first calculation, thus describing the upper limit, not the actual state at the time of use.

Why does raw dried cannabis mainly contain the acid form?

Because that is what comes from the plant and nothing further processes it. Cannabis enzymes finish their work on the acid form, and the conversion to THC occurs without their involvement: slowly during drying and storage, quickly when heated. Therefore, freshly cut flowers primarily carry THCA.

The conversion also occurs when no one triggers it. The acid decomposes over time, and heat and light accelerate this decomposition; with longer storage, some of the produced THC further oxidizes to cannabinol. Measuring only the neutral form would therefore yield different results on the day of packaging and six months later, even if the jar remained untouched.

The sum of both forms is resistant to this variability, and that is why the label provides it. However, it is worth knowing what this number does not cover: it describes the potential of the raw material after complete conversion carried out under laboratory conditions. How much of this potential will be produced in the device and how much will reach the body is not addressed by the declaration, as it is not its purpose.

Hence another consequence for reading the label. The number describes the state from the day of the batch test, not a permanent property of the strain: the same batch measured after a longer time will yield a different result, although the name on the package will remain unchanged. The expiration date is as important here as the percentage itself, and storage conditions affect both of these quantities at once.

Can the number on the label be used to determine the dose for the patient?

No. The declaration describes the composition of one gram of raw material, not the amount that the patient takes, nor the rate at which that amount reaches them. The choice of what raw material and in what form will be used is determined by the attending physician, as the dried material is dispensed only by prescription in the Rpw category.

Percentage and amount are two different quantities, and confusing them is the most common mistake when reading the label. The declaration states what part of the mass of the raw material corresponds to total tetrahydrocannabinol. It does not say how much of that mass will be used or how much substance will enter the bloodstream. The same number with two different methods of administration means two different courses.

Choosing the amount in small steps and how the patient’s tolerance changes over time is described at the neighboring shelf of the declaration. Here, one note suffices: comparing declarations between manufacturers makes sense only if both were derived from the same method of calculation, meaning both are total tetrahydrocannabinol, not just the neutral form.

The declaration refers to dry mass, not to volume or appearance of the material. Two packages described with the same number may differ in grinding, moisture, and the weight of a single flower, which changes how much raw material is actually measured at the pharmacy, even though the percentage on both labels remains the same.

Does the declared percentage change the onset and duration of action?

No, it does not. The declaration determines how much substance corresponds to a gram of raw material, not when the effect begins and how long it lasts; the route of administration determines the course over time. The following description therefore pertains to routes of administration, not this or any other shelf of declarations.

The route of administration determines the course more than the strain itself. After vaporization, the substance passes from the lungs to the bloodstream almost immediately, so the first sensations appear after a few minutes, intensity increases for another ten to thirty minutes, and the whole effect lasts for two to four hours. After ingestion, the raw material first passes through the intestine and liver, so the first sensations are waited for from half an hour to two hours, and the episode lasts six, sometimes eight hours. Hence the most common mistake with oral administration: someone who thinks nothing is happening after thirty minutes and adjusts the dose will receive both doses at once. The above ranges describe the route of administration, not this strain; pharmacokinetic studies for a single cultivar have not been published.

For the reader of the label, the conclusion is that the percentage number and the course over time are two separate things that can easily be conflated into one. The declaration describes the composition of the material before administration, and the above ranges describe what happens afterward and what depends on the route, not the label.

What is known and what is not known about the relationship between raw material potency and effect?

What is known mainly concerns harms, not benefits. Four reviews that can be referenced here primarily deal with non-medical use, and works on therapeutic applications are few and divergent. None of these reviews uses the label declaration as a measure of exposure.

The authors added a disclaimer that weighs more for this page than the result itself: there is a lack of a standardized measure of exposure. Since studies do not measure potency in one way, the pharmacy declaration has no equivalent in this literature, and directly transferring conclusions to one percentage shelf is a guess, not a reading.

The fourth work concerns not so much the effect as the raw material itself.

What adverse effects are associated with higher potency raw material?

There is no separate summary for the declaration of twenty percent. Evidence regarding raw material potency describes broad shelves at once and primarily speaks of psychosis and problematic cannabis use, i.e., the consequences of long-term non-medical use, not symptoms that the patient notes during therapy conducted by a physician.

Reports of adverse effects are collected for a medicinal product with a batch number, not for the strain name, so the following pertains to cannabis as a group of raw materials. The most commonly reported effects are dry mouth, red eyes, and increased heart rate. Less frequently described are dizziness upon rapid standing, daytime drowsiness, and transient worsening of short-term memory, as well as anxiety that increases with dosage. A separate issue is medications taken concurrently, especially sedatives and those affecting coagulation: their assessment requires knowledge of the entire list of preparations, not just the description of the plant. We do not provide the frequencies of these symptoms numerically, as public summaries for cannabis in Poland do not separate them by individual products.

The numbers from the reviews are not frequencies of symptoms, but percentages of works in which a given compound occurred at all.

In studies on therapeutic applications, the picture only partially reverses: benefits for anxiety were noted by 47 percent of them, for depression 48, while 24 and 30 percent of those same works found unfavorable associations simultaneously. The risk of systematic error was assessed as moderate or high in over 95 percent of included studies, so none of these numbers can be read as a measure of risk for an individual patient. How these observations look with even higher declarations, we describe separately.

Frequently asked questions

Does a higher declared percentage mean stronger therapeutic effects?

It has not been shown that a higher declared percentage on the label means stronger or better therapeutic effects. The evidence material regarding the potency of the raw material concerns almost exclusively adverse effects and non-medical use, not effectiveness, and works on therapeutic applications are few and yield mixed results. The authors of both the latest reviews assessed the certainty of evidence as very low. There is also no study that compared two pharmacy dried materials differing only in declared content.

What does the abbreviation THCA mean in the dried material test result?

THCA is tetrahydrocannabinolic acid, which is the form in which the plant actually stores tetrahydrocannabinol. It differs from THC by one carboxyl group, which it loses when heated. In raw, dried flowers, it is this that constitutes the majority of the content.

Why does the label state total tetrahydrocannabinol instead of just THC?

Because both forms occur alongside each other in the raw material, and their proportion changes over time and under the influence of heat and light. The sum of both, after converting the acid with the factor 0.877, is a stable quantity, while the neutral form alone would yield a different result with each measurement.

Where did the number 0.877 come from?

From the ratio of molecular weights: 314.47 for THC versus 358.48 for its acid form. The difference is carbon dioxide with a weight of 44.01, which is released during decarboxylation. The ratio is 0.8772 and in this rounded form enters the calculation of total content.

Do two dried materials with the same declaration have the same content?

Not necessarily. The allowable difference between the measured and declared value is ten percent, so two items described the same may lie at opposite ends of the same range. Comparison makes sense only if both numbers were derived from the same method of calculation.

Does the content change during storage?

The proportion of both forms does indeed change: the acid slowly loses its carboxyl group, and the produced THC oxidizes over time to cannabinol. Heat and light accelerate this process. The declaration covering both forms at once is precisely to ensure that such passage of time does not overturn the result.

Cannabis is a pharmaceutical raw material dispensed by prescription in the Rpw category, and its use is determined by the attending physician. The material is for informational purposes and does not replace medical or pharmaceutical advice. Editorial text: ubucha.