Dosage calculations & extract equivalency in herbal medicine

Compound Tincture of RhubarbOver a number of years of teaching, one of the common issues I’ve noticed is that students often find calculating dosage equivalents rather challenging. It is important to be able to convert between liquid extract quantities and dry herb amounts, and vice versa. So I thought this would be a good place to discuss the issues and provide some techniques to help.

Extraction vs Dry Herb

For hundreds of years extracts have been used in the administration of herbal medicines. In the earliest and simplest forms this usually involved infusions and decoctions, however as tools and methods have developed over the centuries, far more complicated and sophisticated methods are available and commonly used today.

However for lack of a better measure, the most commonly used dosage standard is weight of dry herb material. This is used in most historical and modern texts, where you will see dosage statements such as …

2-4g of dry root or equivalent, three times daily.

The interesting and most important phrase in here is “or equivalent”.

Equivalency

Equivalency implies that another preparation form or extract of a herb is suitable, provided it is deemed to be “equivalent” to this dosage of dry plant material.

By definition an extract removes something and leaves behind something else. Extraction thus changes the chemical profile when compared to the dry herb itself. Many factors can determine the chemistry of the final extract including:

  • solvent (menstruum) – eg. polar or non-polar, or combinations of different solvents
  • duration of maceration of dry material
  • physical size of dry material being macerated
  • method used to extract (eg. percolation, or simple maceration only)
  • concentration steps employed (eg. none, heat, low pressure)
  • and of course the quality of the raw material being extracted.

Therefore in the truest sense an extract can never be completely “equivalent” to the dry plant material, regardless of how it is produced. Nevertheless this concept of equivalency is still used widely (indeed it is included as a concept in the Australian Therapeutics Goods Regulations) due largely to the common desire to employ mostly Galenical extracts.

Galenical Extracts & Selective Extracts

A general principle of herbal medicine is that the activity of the medicine is due to a combination of active chemicals in the plant or the extract. Thus in most cases it is desirable to create an extract which most closely represents the chemical complexity of the dry plant material. Such extracts are often termed “Galenical extracts”, and more recently “full-spectrum extracts”.

However extracts which are not really comparable to the chemistry of dry herb are sometimes used in herbal medicine, in particular in tableting. These extracts are often called “Selective extracts” as their production methods have selectively removed one or more chemicals to a high degree, at the expense of other chemicals. Sometimes so-called “standardised extracts” are in reality selective extracts, as the Australian regulatory definition for standardisation is somewhat loose.

The merits of Galenical and Selective extracts are debated at length in herbal medicine, and are beyond the scope of this document. Suffice to say that general or blanket statements on this issue are usually flawed, and choice of extract can be very dependant upon the desired outcome of the medicine. For example, a selective standardised extract of Silybum marianum has been demonstrated to have excellent efficacy in severe hepatic damage, and also very good safety, making it a useful clinical choice. However in many other cases selective extracts may offer no additional – or even reduced – therapeutic benefit.

Extraction Strength (Drug Extract Ratio)

The strength of herbal extracts are generally expressed as a ratio of dry plant material to final extract quantity, also known as the drug extract ratio (DER). It is expressed in the following format:

X : Y

X = weight of dry plant material

Y = weight or volume of extract (depending upon whether extract is a solid/dry extract, or a liquid extract)

The concept here is that the essential activity of the dry plant material (X) is found in the quantity of extract (Y). Or in other words, Y quantity of the extract is equivalent to X quantity of the dry plant.

Remember that ratios are fractions – ie. a 1:2 is the same as ½, a 1:3 is the same as 1/3 and a concentrated 4:1 is equivalent to 4.

DER Dry Herb Weight Extract Weight or Volume Extract Description
1:1 1kg 1L liquid extract (also by convention 1:1’s are known as a fluid extracts)
1:2 1kg 2L liquid extract
1:3 1kg 3L liquid extract
1:5 1kg 5L liquid extract; 1:5’s and below are often termed tinctures, although this is technically more determined by method of extraction than actual DER (i.e. technically tinctures are produced only through maceration)
1:10 1kg 10L liquid extract; tincture
2:1 2kg 1L concentrated liquid extract
4:1 4kg 1kg semi-solid extract – hence the change to using weight as a measurement of extract quantity rather than volume
8:1 8kg 1kg solid or semi-solid extract (depending upon consistency)
25:1 25kg 1kg solid extract
8-9:1 8-9kg 1kg solid or semi-solid extract; when extracts from different batches are combined to obtain specific outcomes (eg. standardisation or quantification of specific phytochemicals in the final product), sometimes a range is used as the extract ratio; this can make dosage calculations based on dry herb quantities difficult

 

Extract Equivalency & Dosage Calculations

With multiple dosage forms now being common in herbal medicine, it is essential that clinicians can convert between extract and dry herb equivalency, and vice-versa. This process is very simple, and it is essential that all herbal students and clinicians can do these conversions quickly and accurately.

For instance, need to be able to interconvert between …

  • an Echinacea tablet stated to contain 200mg of a 4:1 extract, with a dose of 1 tablet three times daily
  • an Echinacea purpurea radix liquid extract stated to be a 1:2
  • a textbook recommended dose for Echinacea purpurea radix of 1-2g three times daily

So let’s look first at some rules to help you make these conversions.

1) Converting from dry herb to extract (DIVIDE)

An example of this would be:

“You have a 1:3 extract and need to give 1.5g of dry herb equivalent. What dose of the 1:3 extract should you use?”

X (dry herb quantity) = 1.5g
Y (extract quantity) = unknown
Extract ratio: 1:3 (or 1/3)

Rule: Divide the dry weight by the extract ratio

1.5g divided by 1/3 = 4.5mL

Therefore the answer is 4.5mL

2) Converting from extract to dry herb (MULTIPLY)

An example of this would be:

“You have 2mL of 1:3 extract, what is the equivalent quantity of dry herb?”

X (dry herb quantity) = unknown
Y (extract quantity) = 2mL
Extract ratio: 1:3 (or 1/3)

Rule: Multiply the extract quantity by the extract ratio

2mL multiplied by 1/3 = 0.66g

Therefore the answer is 0.66g

3) Don’t Get Your Units Messed Up!

It is essential that you keep your units correct throughout your calculations. When you look at the table given on page 2, you see that a 1:2 extract is said to be 1kg : 2L. This is the same as:

1000g : 2000mL (because there are 1000g in 1kg and 1000mL in 1L)
1g : 2mL
1000mg : 2mL
500mg : 1mL

Some Examples

Here are some examples of applying the methods discussed above.

1) What is the dry herb equivalent of 2mL of a 1:2 extract?

This is an “extract to dry herb” question, so we multiply by the extraction ratio.

2mL multiplied by 1/2 = 1g

Therefore the answer is 1g

2) What is the 1:5 liquid equivalent of 3g of dry herb?

This is a “dry herb to extract” question, so we divide by the extraction ratio.

3g divided by 1/5 = 15mL

Therefore the answer is 15mL

3) What is the dry herb equivalent of 150mg of an 8:1 extract?

This is an “extract to dry herb” question, so we multiply by the extraction ratio. But remember that we need to keep our units the same!

150mg multiplied by 8/1 = 1200mg

Therefore the answer is 1200mg (or 1.2g)

20 Comments

  1. Reply

    Shayne

    September 20, 2014

    Ian, you've addressed this issue with real finesse. Of course, there are several threads to the more complete topic of crude herb to liquid dosage conversion that you did not address in your article (e.g. fresh versus dry and drop dosage calculations). But, what is addressed, is framed splendidly.

    As you point out, all extraction is selective. Even if we extract all soluble constituents, at the very least we are leaving behind the spent marc, which may in itself provide benefit, if we were to consume the plant as part of a plant-based diet. For what it's worth...the way I see it, there are 3 common motives behind employing purposefully selective extraction. First, in commerce, selective extraction may be driven by some effort to increase profitability, by maximizing the yield of a compound being characterized for so-called 'standardization'. As a manufacturer, if I use a solvent composition and extraction methodology that yields an increase of a plant's biomarker compound(s) by 10%, then I can use 10% less of that extract in my finished product...and still meet the label claim for the biomarker(s). Secondly, it may actually be advantageous when using some of the so-called 'toxic botanicals' - that have a narrower TI - to know precisely how much of a marker compound is in each dose. Finally, selective extraction can be employed to produce an extract tailored for a specific therapeutic outcome. Taking Podophyllum for example - according to the Eclectics, if extracted with ethanol, you yield the plant's resins, which are highly cathartic. Conversely, extract Podophyllum with hot water and you yield more of the lectins, which are considered to be highly alterative. So, are you extracting Podophyllum to provide a laxative or a 'blood purifying' effect? The answer will determine what you selectively extract.

    • Reply

      Ian Breakspear

      September 21, 2014

      Hi Shayne!

      Thanks for your comments, and I thoroughly agree with what you've said about selective extraction. Everything from the solvents used, duration of maceration/percolation, temperature of the maceration, all can play a significant role in altering the final chemistry of the extract, and thus the reality of the term "equivalency".

      Extending upon your statement re maximising the yield of a specific constituent in making a "standardised" product, sometimes a similar process is used with poor quality raw material to reach the desired "standardisation specification". Which is obviously a shame in the context of holistic phytochemistry.

      I think it is important that practitioner awareness of some of the issues is increased, because at the end of the day, clinical effectiveness is intimately linked with the quality of the medicines we use. And each and every one of our patients deserves the best medicine we can give them.

  2. Reply

    Maya

    November 2, 2018

    Hello,
    Very helpful information. Thank you.
    I am a little confused..
    I have 1000 kg Nettle (for example) and I want to make liquid extract from it, the ratio will be 1:4
    So,what should be the quantity ot obtained liquid extract? 4000kg or am I wrong?

    • Reply

      Ian Breakspear

      November 4, 2018

      Hi Maya!
      Thanks for your comments.
      Yes, essentially your calculations are correct. If you have 1000kg of dry herb material, and desire to make a 1:4, then the quantity of final liquid will be 4000L (because it is a liquid extract, we generally measure the output in volume rather than mass/weight). Obviously though that would be a HUGE batch! ;-)

  3. Reply

    Maya

    November 5, 2018

    Thank you so much, Mr. Breakspear :-)
    What about dry extracts? There is other calculation or it is the same? (If I have 1000 kg raw material) I will get 4000L liquid extract but if I want dry extract, I should evaporate the solvent and what is the ratio there?

    • Reply

      Ian Breakspear

      November 5, 2018

      Hi Maya,

      Pleasure! With dry extracts the principles are the same, however if the extract is a solid or semi-solid, then the final extract mass (instead of volume) is used in the ratio. As an example, say you have 10kg of dry herbal material, and you extract it using whatever choice of solvents, then evaporate the liquid until you have 2kg of dry extract, you would have a 10:2 (i.e. 10kg of dry material, producing 2kg of extract), or as it would usually be written, a 5:1 (i.e. 5kg producing 1 kg).

      Of course the concentration step is a major confounding factor in the actual activity - whilst you might have a 5:1 mathematically, the real question is do you actually have an extract that is 5 times stronger than the original dry material? Whilst obviously the choice of solvent and method of extraction plays a role here, the concentration step adds another factor, and the outcome is largely dependent upon the active chemistry of the plant. For example, if the actives are volatile, then using heat and/or vacuum concentration will result in not just the solvent being removed, but also a large proportion of the actives. Likewise if the actives are unstable at higher temperatures, then you have to be very careful to ensure that those temperatures are not reached otherwise the constituents will degrade.

      It is for these reasons that many of the concentrates sold on the world herbal materials market and incorporated into powders and tablets and capsule, often don't work in clinical practice as well as you'd expect. Many clinicians don't realise this, and companies rarely discuss this issue openly. Of course there are exceptions (often where the company has invested considerable money and time into research and development, including benchtop and clinical research) but overall these are the exceptions, rather than the rule.

  4. Reply

    Joanna

    November 14, 2018

    Hi Mr. Breakspear, please help me with an argument regardind the follwings: I have two extracts, an 10:1 extract and an 5:1 extract from which I obtain the same mass of solid extract, let's say, 5g of solid extract. In terms of comparison, could I say that the 10:1 ratio is more concentrated than the other, just because I use more herb? Taking into account that the final extract quantity is the same, I would actually presume that the 5:1 extract is obtained from a herb of a higher quality, rather than say that the first one is more concentrated.
    Thank you very much and I am looking forward for your opinion!

    • Reply

      Ian Breakspear

      November 16, 2018

      Hi Joanna!
      Yes, the 10:1 is definitely more concentrated than the 5:1 - if you have 5g of a 10:1 extract, then it is equivalent to 50g of dry herb, whereas 5g of a 5:1 would be equivalent to 25g of dry herb.

      However it is important to know this is a simple mathematical relationship - it does not take into account the raw material quality, or the efficiency of the extraction. It is certainly possible to have 5g of a 5:1 made efficiently from good raw material, which is more efficacious than 5g of a 10:1 made with less-than-ideal solvents and methodology and poor quality raw material.

      This is why dry herb equivalency calculations are important, but cannot always be relied upon when comparing products. It is also why many herbalists find better results from 1:1 or 1:2 liquid extracts than some tablets, even when using the same dry herb equivalent amount. It is not because of better absorption, but because in creating the concentrate to go in the tablet, the desired phytochemical profile has been sacrificed in order to get a more impressive looking drug extract ratio.

  5. Reply

    Dorota

    January 7, 2019

    Dear Mr. Breakspear, could you be so kind and please help me with an calculation regardind the follwings: I have the following composition and I would like to know the final amount of 1 tbl.
    Rhodiola rosea 5% rosavins standard RR05S
    o Part of the plant used: root
    o Active titration: 5% rosavins
    o Plant extract ratio: dry extract 7-10/1 (native extract)
    o Quantity per unit: 144 mg
    o Quantity of equivalent dry plant per unit: 1008 mg
    Which type of calculation I can use for this mathematical case?
    Thank you very much for your help and reply!

    • Reply

      Ian Breakspear

      January 11, 2019

      Hi!

      Interesting question, but one which I cannot answer completely due to the fact that a tablespoon is a measurement of volume not mass, so without some kind of density value for the powdered extract, it is impossible to calculate exactly. But I can help you towards finding the solution yourself.

      Firstly we should consider some background explanation of the specifications you have provided. The drug extract ratio is declared as 7-10:1 which means that there is some variation in dry herb quantity used batch to batch in the extraction process. In this case, the variation means that between 7kg and 10kg of dry herb is used to make 1kg of final extract. This variation is likely necessary in order to ensure that each batch can be standardised for 5% rosavins, as natural raw material will have a natural variation in constituent concentration from harvest to harvest, or depending upon where it is grown.

      The information you provide says that the "quantity per unit" is 144mg, although what "unit" they are referring to is unclear. What is clear is that they say for that "unit" it is equivalent to 1008mg of dry herb material. This means that they are basing their calculation off the bottom end of the drug extract ratio - i.e. 7:1, rather than the upper end of 10:1. In case you need it, the mathematics for this calculation are:

      X (dry herb quantity) = 1008mg
      Y (extract quantity) = 144mg

      DER = X divided by Y = 7 (i.e. the drug extract ratio is 7:1)

      Now to the crux of your question: how much herbal material is in one tablespoon? You can only calculate this by converting the measurement of a tablespoon into a measurement of mass. Therefore what I would suggest is that you obtain a proper tablespoon measurement (you can often purchase these at cooking supply stores - but check whether they are meaning a US or an Imperial tablespoon measure as there is a slight difference in volume), and a set of digital scales. After placing a cup or dish on the scale and zeroing the scale, carefully measure out 5 tablespoons of your Rhodiola powder and put them in the cup/dish, then note the weight reading on the scale. Divide this by 5 and then you have the weight of powder per tablespoon (I'm suggesting doing 5 tablespoons rather than one to improve accuracy, as most digital kitchen scales are slightly less accurate at low weights). If you then divide this by 144mg then multiply by the DER (7) you'll have the dry herb equivalency of Rhodiola in one tablespoon of this extract.

      These calculations should work unless there is some complication in what they refer to as a "unit" in their statement "quantity per unit". It is possible that they define a unit as a tablespoon or a teaspoon or some other measurement, and that in that "unit" there is 144mg of extract and the rest of the volume is made up of an excipient. Hopefully this is declared on the label or the product specifications - if it is not, then there is no way of calculating the dry herb amount in a tablespoon.

      I hope this helps!

  6. Reply

    James Maloney

    January 16, 2019

    Hi Ian, Could you please let me know if I have calculated this correctly please. From dried herbs to a liquid extract. 70mg of powdered herbs = 1.4ml in liquid extract if the liquid is 1:2?

    • Reply

      Ian Breakspear

      January 24, 2019

      Hi James.
      Not quite - the only issue you've made is in regards to units of measurement, which is a very common mistake when first working out these calculations. The best bet is to convert the milligram quantity to grams if you are wanting extract equivalency in millilitres. So 70mg = 0.07g

      Then apply the calculation as stated in my blog post above and the equivalent dosage of a 1:2 would thus be 0.14mL (so you got the numbers correct, just out by a factor of 10 as a result of the units issue).

  7. Reply

    Manish

    January 17, 2019

    I want to know about hedera helix. I want to make syrup of hedera helix (ivy leaf) equivalent to 43.75 mg/ml dry leaf extract.
    My extract ratio is 10:1

    • Reply

      Ian Breakspear

      January 24, 2019

      Hi Manish,

      I'm assuming you're starting with dry powder 10:1 extract, then intend to mix and dilute it with a sugar and water mixture to turn it into a syrup.

      Firstly you need to work out how much 10:1 you need to be equivalent to 43.75mg of dry leaf. So this part of the problem is a dry herb to extract conversion. Therefore you divide the dry herb amount by the extract ratio, which gives you 4.375mg of the 10:1 extract. Thus you will need to ensure that in each millilitre of the final syrup there is 4.375mg of the 10:1 extract.

      The next step is scaling this up to a quantity which would be relevant to prepare yourself. So as an example, let's say you wanted to produce a litre of the syrup. This is 1000mL of syrup. Therefore you will need 1000 x 4.375mg of the 10:1 extract, or 4375mg, which of course is 4.375g. You would add this to your mixing vessel, and then add enough pre-prepared syrup base to bring the final volume up 1000mL. It is important for accuracy that you don't just add 1000mL of syrup - that would mean the total end volume would be 1000mL plus whatever volume the 4.375g of 10:1 consumed, which would mean that there would in fact be slightly less that 43.75mg of dry leaf equivalent per millilitre. Whilst in this case the difference would be minute, it is a good habit to be accurate when possible.

  8. Reply

    Dakota

    February 7, 2019

    Hi Ian! This is a great article! I just finished a course of study as a student of herbal medicine. I generally work with herbs by dry weight in the form of infusions and decoctions. I also generally measure out my amounts in terms of ratio of parts, for example:

    2 parts red clover bud
    1 part nettle leaf
    1 part raspberry leaf
    .5 part peppermint leaf

    That way it is flexible regardless of the size of batch. But I have someone that wants me to break it down into milligrams per dose. I am certain I am over-thinking this entirely, mostly because math has never been my strength.

    Do you have any advice as to how to simply the process? Thanks.

    • Reply

      Ian Breakspear

      February 9, 2019

      Hi!

      If you're using a ratio of parts by dry weight (and not volume), then you are part way there in your calculations.

      The key to the next step in the calculations is knowing how your patient measures out their dose, or how you've stipulated for them to measure it out. Are they using volume (i.e. 2 heaped teaspoons, or similar)? If that is the case, you need to take your mixed herbs, and measure out how much a teaspoon (or whatever volume measurement you are stipulating in your dosage for the patient) weighs. I'd suggest using sensitive digital kitchen scales, putting a container on the scales and zeroing them, then adding 10 teaspoons of the mix into the container. Note the weight on the scales, then divide by 10 to get the average weight of a teaspoon.

      Now let's say your teaspoon of mixture ends up weighing 3g (just as an example). You would divide that by 4.5 which is how many "parts" by weight are in that teaspoon, giving you a result of 0.67 (rounded).

      You then apply this to the number of parts of each herbs:

      2 parts red clover x 0.67 = 1.34g
      1 part nettle x 0.67 = 0.67g
      1 part raspberry x 0.67 = 0.67g
      0.5 part peppermint x 0.67 = 0.34g

      Total = 3.02g (just over 3g due to the rounding)

      So if the patient is using 2 teaspoons per cup, or 5 teaspoons to make a day's decoction, or whatever, you can now work out how much herb they are getting in that cup, or in that day's decoction. Obviously to convert to milligrams, multiply all the results - which are in grams - by 1000.

      I hope that helps!

  9. Reply

    marianne

    February 17, 2019

    Hi Ian,

    Thank you for this very helpful article. I have a complicated question & one that I am unable to figure out. Please could you help me if possible? I am trying to find how much a 300mg Hypericum LI160 tablet (Jarsin brand) would be in 1:2 45% Hypericum perforatum tincture equivalent? The only data I can get on the Jarsin tablet is 300mg dried extract from Hypericum perforatum (3-6:1); Extract Methanol 80% (v/v). Even an approximation would be extremely useful! Many thanks in advance. Marianne

    • Reply

      Ian Breakspear

      March 10, 2019

      Hi!

      Yes this one is a bit complicated. Jarsin 300 (or LI 160) is a standardised extract, and as the specifications indicate, the DER can vary between 3:1 to 6:1 in order to ensure consistency from batch to batch (given that raw Hypericum can vary from harvest to harvest). Therefore direct comparison to a 1:2 of Hypericum is difficult, and some would say questionable as even if the dry herb quantity could be matched, the extraction methods are different, and obviously raw material sources would likely be different.

      But if you are looking for an approximation, the way I would normally look at it is that the DER range and go in the middle - so this would be a 4.5:1 (i.e. 4.5kg of dry Hypericum would make 1kg of final extract).

      If each tablet has 300mg of this extract, that would mean that it would be approximately equivalent to 4.5 x 300mg = 1,350mg of dry Hypericum (or 1.35g).

      To convert this to a 1:2, you would then apply the formulae I have outlined in the blog post - i.e. dry herb quantity divided by DER. So this would be 1.35g divided by 1/2 = 2.7mL of a 1:2 would be roughly equivalent to 1 tablet. If you were converting this to a weekly dosage as most herbalists and naturopaths do, you would need to consider how many tablets of Jarsin 300 is recommended per day. This is usually 3 tablets per day. So you'd be looking at 8.1mL of a 1:2/day or approximately 55mL/week (which is quite high when you consider the manufacturer's recommendations for most 1:2's on the Australian marketplace).

      Remember though that this is very much an approximation.

      Hope that helps!

  10. Reply

    Jill

    February 22, 2019

    Hi Mr Breakspear, Your post is very clear thank you for sharing. I am wondering about fresh plant extracts though? How can I be sure about how many grams of herb I am taking if I am taking a 1:1 extract of a plant that has a 50% water content. So if I put 100g of chickweed in 100ml of 95% ethanol and took a 5ml dose would i be getting 2.5g of chickweed? or would i have to do some other equation to account for the water content?

    • Reply

      Ian Breakspear

      March 10, 2019

      Hi Jill,

      If you are extracting fresh plant (as opposed to just fresh juicing it), then more calculations need to be conducted as the general consensus is to declare DER as dry herb to final extract, not fresh herb to final extract.

      However an argument can be made for declaring it as a fresh plant. So in your example if you took 100g of chickweed, and added 100mL of 95% ethanol (and stuck it in all in a blender for example), you would then measure out the final quantity of liquid after filtering and pressing. Let's say you ended up with 140mL (some water and ethanol is always lost in the process), then you would have the equivalent of 100g of fresh chickweed in 140mL of final extract. This would equate to a 1:1.4 extract of fresh plant. So in a 5mL dose you would have the equivalent of 3.5g of fresh chickweed (i.e. 5mL x 1/1.4).

      If you wanted to look at dry herb equivalence then you need to do more processing and calculations. This involves taking a small sample of fresh chickweed, then you weigh it, and then heat it in a low oven until it is full dry. Then weigh it again and calculate the percentage lost in the drying process. This then enables you to convert fresh to dry herb equivalencies (it also enables you to know exactly how much water is in the fresh plant, and thus when you add the 95% ethanol it and blend the fresh herb, it also enables you to do the full calculation of the percentage ethanol in the final extract). I won't go into all of these calculations here - perhaps that might be the topic of a future blog post if there is the demand! ;-)

      Hope this helps.


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