What Is Fulvic Acid?

Fulvic acid is the fraction of humic substances that stays dissolved in water at every pH. Humic substances are what remains when microorganisms have spent a very long time breaking plant and animal matter down in soil, water, peat and rock; soil scientists sort the result into three fractions by solubility, and fulvic acid is the smallest, most soluble and most acidic of the three. It is not a single compound. It is a family of small organic molecules, rich in oxygen and in acidic groups, that bind metal ions and move them, which is why it appears in fertilisers, in water chemistry, and on the label of every jar of shilajit.

That is the definition, and everything the supplement trade says about fulvic acid is an extension of one part of it: the metal binding. This article explains the chemistry that gives the substance its name, how the percentage on a label is measured and why two laboratories can disagree about the same jar, where fulvic acid comes from in supplements, what the mineral-carrier idea is and how far it has been tested in people, and where the honest evidence stops. If you want to know what the number on a label is worth as a buying signal, that is a separate question and it has its own article.

Humic substances, and the test that sorts them

The International Humic Substances Society, which maintains the reference samples the field calibrates against, describes humic substances as “major components of the natural organic matter in soil and water as well as in geological organic deposits such as lake sediments, peats, brown coals and shales.” They are the dark, complex material that gives topsoil its colour and river water its tea tint. They form when plant material is broken down by microbes about as far as it will go and the fragments recombine into large, irregular molecules that no longer resemble anything that was alive.

Nobody can write a structural formula for a humic substance the way you can for glucose, because there is no single molecule to draw. So chemists defined the fractions by what they do in the laboratory rather than by what they are. The IHSS procedure extracts humic material from soil with a strong base, then acidifies the extract. In the society’s own words, “Humic acids are insoluble at low pH, and they are precipitated by adding strong acid”, while the fraction that stays dissolved is the fulvic acid, and “Humin cannot be extracted with either a strong base or a strong acid.”

So the three fractions are:

Fraction	Behaviour in water	Typical size
Humin	insoluble at any pH	largest, tightly bound to mineral matter
Humic acid	dissolves in alkali, precipitates at pH 1 to 2	intermediate, roughly 5 to 10 kDa in the shilajit literature
Fulvic acid	dissolves at every pH	smallest, hundreds to a few thousand daltons

A 2012 review of shilajit in the International Journal of Alzheimer’s Disease sets out the same division and adds the sizes: humic acid “is soluble in water under alkaline conditions and has a molecular weight of 5 to 10 kDa”, while fulvic acids are smaller and remain in solution across the pH range. That size difference is not a detail. It is why fulvic acid can do things in solution that humic acid cannot, and why it is the fraction people care about.

The word “acid” is literal. Fulvic molecules carry many carboxyl and phenolic groups, which give up protons in water, which makes a fulvic solution acidic, and which are also the sites where metal ions attach. Small, soluble and covered in charged groups: those three properties explain everything else on this page.

Why it binds minerals, and what that means in soil

In soil, fulvic acid is part of how minerals move. Metal ions such as iron, zinc, copper and manganese are poorly soluble on their own in most soils; bound to a small organic molecule with several acidic groups, they form a soluble complex that water can carry and a root can take up. This is ordinary, well-described soil chemistry, and it is why humate products from lignite and leonardite deposits are sold to farmers as soil conditioners: they keep trace elements in a form plants can reach.

The 2026 study of shilajit in the Journal of Trace Elements in Medicine and Biology shows the same chemistry inside the resin. Twelve samples were analysed by ICP-MS coupled to size-based separation, and the authors found that “most metals were associated with low-molecular-weight” complexes. In other words, the calcium, magnesium, iron and zinc in shilajit are not sitting there as free salts; they are attached to the fulvic and other small organic fractions. Calcium, the most abundant element, was found as a complex with lactic acid. The mineral content of shilajit and the fulvic content are not two separate facts about the material. They are the same fact seen from two sides.

That is the honest version of the “fulvic acid carries minerals” statement. It is true of the material in the jar. Whether it is true inside a person is a different question, addressed below.

Where fulvic acid comes from in supplements

There are three commercial sources, and the source matters more than the percentage.

Shilajit. The humic exudate that seeps from mountain rock in the Himalaya, Hindu Kush, Altai and Caucasus, described in full in what is shilajit. The 2012 review puts its humic content at around 60 to 80 per cent, with fulvic acid dominant, alongside dibenzo-alpha-pyrones and a mineral fraction. The European Commission’s novel food consultation on mumijo, the European name for the same material, describes it as “characterised by the humic and fulvic acids, non-humic components (e.g. dibenzo-alpha-pyrones) and diverse other minerals it contains”, and records that it is not a novel food when used in food supplements because Czechia documented its use in supplements before 1997.

Leonardite and humate deposits. Oxidised lignite, mined in North America, Europe and elsewhere, is the source of most agricultural humic and fulvic products and of many “fulvic mineral” drops. The chemistry is the same class of molecule from a different geological history, usually with a lower fulvic fraction and a different metal profile.

Peat and aquatic humic material. Bog water, peat extracts and some mineral waters carry dissolved humic substances. A 2003 paper in BioFactors on humic substances in Danish drinking water is a useful reminder that these molecules are ordinary in the environment: iodine in Danish groundwater was found bound to humic substances leached from marine sediments, and the authors note that humic material from coal and shale in other parts of the world has been reported to interfere with thyroid function in populations drinking it. The source geology decides what the fulvic fraction carries.

For a buyer the practical rule is simple. The fulvic percentage tells you how much of one fraction is present. The source, and the laboratory report on that specific batch, tell you what came with it, and the heavy metals article is where that is dealt with.

Fulvic acid in food and water

A question that comes up in several languages is whether fulvic acid is in food. Strictly, yes, in traces: any vegetable grown in humus-rich soil and any unfiltered water from a peaty catchment carries some dissolved humic material, which is where the tea colour of upland streams comes from. But it is not a nutrient with a dietary reference value, no food is a meaningful source of it, and no public health body recommends an intake of it. The plants that grew in fulvic-rich soil took up the minerals the fulvic acid delivered; they did not take up the fulvic acid as a nutrient for you.

The Danish drinking water study is the clearest illustration of how ordinary these molecules are in the environment. The authors describe humic substances as “heterogeneous mixtures of naturally occurring molecules, produced by decomposition of plant and animal tissues”, found in groundwater across the country, and note that the amount and the character of the humic material depended on the sediments the water had passed through. Fulvic acid is not exotic. It is the background chemistry of soil and water, and the supplement trade sells a concentrated form of it from one of three geological sources.

That framing matters for expectations. A concentrated fulvic extract is a concentrated version of something in every glass of stream water, not a vitamin the modern diet has lost, and any page that describes it as a missing nutrient is describing something that does not exist.

How the percentage is measured, and why laboratories disagree

Because fulvic acid is defined by a separation procedure rather than a formula, the number you get depends on the procedure you run. Four families of method are in use: the classical alkaline extraction and acid precipitation, gravimetric methods that weigh what is left, spectrophotometric methods that read colour or ultraviolet absorbance, and chromatographic methods such as HPLC that separate the fraction and quantify it against a standard. The colourimetric methods in particular are known to over-read on dark materials, because anything that absorbs light at the measured wavelength counts as fulvic acid whether it is or not. A jar advertised at “80 per cent fulvic acid” by one method may read 40 per cent by another, and neither laboratory has made a mistake.

This is why a percentage without a method is not a measurement. Our supplier’s laboratory certificate for the resin we sell reports 73.8 per cent fulvic acid and 14.7 per cent humic acid, and it names the method, HPLC, on the same line. It also reports 14.3 per cent moisture and 11.8 per cent ash, so the reader can see that the fulvic and humic figures together account for roughly nine tenths of the material and the mineral fraction for about a tenth. That is what a usable number looks like: a value, a method, a batch, a laboratory. The label-literacy question, what a stated percentage is worth and what to ask a seller, is the subject of fulvic acid benefits, which names the methods and how far two of them overstate.

What has been tested in people

Here the chemistry ends and the claims begin, so it is worth being precise about the boundary.

The strongest human data on fulvic acid come from shilajit trials, because shilajit is mostly fulvic acid and it is the form people take. Those trials are audited one by one in shilajit benefits; in outline, they measured retention of strength after fatigue in young men, androgen levels in middle-aged men, a collagen synthesis marker, gene expression in muscle and skin, skin blood flow, bone mineral density in postmenopausal women with osteopenia, and time to bone union after surgery, in groups of 25 to 160 people, over 28 days to 48 weeks. Those are results about a whole resin, not about fulvic acid in isolation, and none of them measured mineral absorption.

On fulvic acid itself, a 2018 review in the Journal of Diabetes Research by Winkler and Ghosh is candid about the state of the field. The authors set out to examine “the available peer-reviewed research on fulvic acid” and “its anecdotal health claims”, and their summary is that “available research has been minimal”. They describe the anecdotal claims, that fulvic acid modulates immune function, influences the oxidative state of cells and affects gut function, as claims from traditional use and from cell and animal work, and they call for research rather than reporting results. A review that concludes by asking for trials is telling you the trials have not been done.

That leaves the mineral absorption claim, the one on every label, in a specific state. The chemistry is established: fulvic acid binds minerals into soluble complexes, in soil and in the jar. The physiology is unproven: no controlled human trial has shown that a mineral taken with fulvic acid is absorbed better than the same mineral taken without it. The claim is reasonable. It is not demonstrated, and under Regulation (EC) 1924/2006 no health claim for fulvic acid is authorised in the EU, which the European Food Safety Authority’s register makes easy to check. Any page that tells you fulvic acid “increases absorption by 60 per cent” or similar is quoting a figure that does not exist in the human literature.

What is not known, and who should be careful

Dose. There is no established dose of fulvic acid as such. The shilajit trials used 250 mg to 1,000 mg of whole resin or extract per day, and a 73.8 per cent resin at 300 mg delivers roughly 220 mg of fulvic acid, but nobody has titrated fulvic acid alone in people. Practical dosing is covered in how to take shilajit.

Long-term use. The longest shilajit trial ran 48 weeks and reported no serious adverse events at 250 mg or 500 mg per day. Beyond a year there is no evidence either way.

Iron. Fulvic-bound iron is still iron. Shilajit is iron-bearing, and anyone with haemochromatosis or another iron-overload condition should not take it or any fulvic product derived from it.

Thyroid. The BioFactors paper is the reason to mention it: humic substances from certain geological sources have been associated with thyroid disturbance in populations drinking them in water over years. That is a population observation about environmental exposure, not a finding about supplements, and no supplement trial has reported a thyroid signal. If you have a thyroid condition or take thyroid medication, it is a reason to speak to a doctor first rather than a reason to panic.

Pregnancy, breastfeeding, children, medication. No data. Avoid in pregnancy and breastfeeding, do not give to children, and ask a doctor or pharmacist before combining with prescribed medication.

Contamination. This is the one that actually matters. Fulvic acid from a purified, tested source has no established toxicity at supplement doses. Fulvic acid from an untested source can arrive with lead, arsenic, mercury and thallium, because the same chemistry that binds nutrient minerals binds toxic ones. The molecule is not the risk. The source is.

The short version

Fulvic acid is the water-soluble fraction of humic substances, the small, acidic, metal-binding molecules left after plant matter has decomposed for a very long time. It is defined by a solubility test, not a formula, so a percentage means nothing without the method beside it. It is the largest component of shilajit and the reason shilajit’s minerals are in a soluble, bound form. Its ability to carry minerals is established in soil and in the jar and untested in people, and no health claim for it is authorised in Europe.

If that is the honest version you were looking for, what a fulvic percentage on a label is actually worth is the next page, how to take shilajit is the practical one, and the heavy metals question is the one that decides whether a given jar is worth opening. Our shilajit resin is sold with the HPLC figures and the metal panel on the same certificate, linked from the page.