Heavy Metals in Collagen Supplements: What Testing Shows, What It Means Per Scoop, and How to Check a Product

Written by Dimitrun Irene. Updated October 29, 2026.

Collagen supplements can contain trace amounts of lead, arsenic, cadmium and mercury, but the published testing shows most products sit well below safety limits, and the problem is concentrated in a minority of products rather than in collagen as a category. The best independent data come from two sources. In 2020 the Clean Label Project tested 30 collagen products bought on Amazon and found measurable arsenic in 64%, lead in 37% and cadmium in 17%, with 4 products (13%) exceeding the strict California thresholds it used. In 2025 Italian researchers measured marine collagen supplements and found arsenic averaging 0.59 mg/kg and lead 0.13 mg/kg, with no sample above EU legal limits and every estimated daily dose below tolerable intakes. Metals get into collagen because collagen comes from animal bone, hide, skin and scales, tissues that accumulate whatever the animal was exposed to. This guide translates the lab numbers into micrograms per scoop, explains why arsenic in fish collagen is less worrying than it sounds, and shows how to check a product before you buy.

Collagen supplements are made from the connective tissue of cattle, pigs, chickens or fish: hides, bones, skin and scales. Bone is a reservoir for lead, which the body stores there in place of calcium, and fish accumulate arsenic and mercury from seawater and their diet. Extraction in hot water pulls collagen out of these tissues, and some of the minerals come with it. Hide- and skin-derived collagen generally carries less mineral than bone-derived collagen, because skin does not store lead the way bone does, and processing steps such as demineralisation with acid, filtration and ion exchange remove much of what remains. The finished peptide powder is therefore only as clean as two things: the raw material and the purification. Neither is visible on a standard label. How bovine peptides are made, from hide to powder, is covered in bovine collagen peptides, and the differences between animal sources in marine vs bovine collagen peptides.

The two main studies reach compatible conclusions from different angles. The Clean Label Project, a non-profit, used California's Proposition 65 levels, which are among the strictest in the world and are designed to trigger warning labels, not to mark the boundary of harm. On that basis 13% of products failed; one chocolate-flavoured collagen protein exceeded both the cadmium threshold (9.17 µg against 4.1 µg) and the lead threshold (1.57 µg against 0.5 µg) per serving. Industry groups criticised the work as a non-peer-reviewed white paper and the arsenic headline as sensational, since none of the 64% of products with measurable arsenic exceeded the 10 µg threshold used. The 2025 Italian study was peer-reviewed and focused on marine collagen, the source most people worry about; it found the same broad picture of low-level presence, wide variation between brands, and no product above EU legal limits.

Laboratory results are reported in milligrams per kilogram of powder, which is meaningless to anyone holding a scoop. The conversion is simple: multiply the mg/kg figure by the grams you take and you get micrograms. A 10 g scoop of a powder with 0.13 mg/kg of lead delivers 1.3 µg of lead. The table applies the average values from the 2025 study to common doses and sets them against the limits that regulators and testers use.

Two caveats keep this honest. Averages hide the outliers, and the products that failed in testing were the outliers; a single bad product can contain several times the average. And context matters: everyone already has a background exposure to lead and arsenic from ordinary food and water, so a supplement adds to an existing exposure rather than creating a new one. The useful takeaway is that a clean product at a normal dose adds very little, while a poorly sourced product at a high dose, or several collagen products stacked together, can add a meaningful share. The practical upper limit on how much collagen to take is discussed in can you take too many collagen peptides and on our collagen overdose page.

Arsenic is the metal most often found in collagen, particularly in fish collagen, and it makes the most alarming headlines. The chemistry softens the picture. Arsenic in seafood is mostly organic arsenic, chiefly arsenobetaine, which the body excretes largely unchanged and which is considered of low toxicity. The form regulators set strict limits for is inorganic arsenic, found in groundwater and rice. Standard tests report total arsenic, which lumps the two together; that is why ConsumerLab's method screens for total arsenic at 10 µg per day and only then measures the inorganic fraction. A marine collagen with a high total-arsenic figure may contain very little of the toxic form. That does not mean arsenic can be ignored, but it does mean a total-arsenic number on a marine product needs the inorganic figure beside it before it means much.

The evidence does not support a blanket rule that one animal is always cleaner. The 2025 study found significant variation between brands, and neither study showed that the animal source alone predicted the result. What does hold is that tissue matters (skin and hide rather than bone), that smaller, shorter-lived fish accumulate less mercury than large predators, and that testing beats assumptions. The 'grass-fed' label, often marketed as cleaner, describes how the cattle were raised, not what a lab found in the powder, as explained in grass-fed collagen.

The full checklist for choosing a collagen product, including dose, type and source, is in how to choose collagen peptides.

Heavy metals in collagen supplements are real but usually small. Independent testing finds traces of arsenic, lead and cadmium in many products, most comfortably below safety limits, with a minority, about one in eight in the largest US test, exceeding California's strict thresholds. Lead is the metal to watch, bone sources and flavoured protein blends carry more risk, and arsenic in marine collagen is mostly a low-toxicity organic form. Ask for a certificate of analysis, convert it to micrograms per scoop, prefer third-party certified products, and keep the dose to the 10 to 15 g the trials used rather than stacking products. How collagen peptides are made and what they are is explained in what collagen peptides are, and how the collagen types compare in multi-collagen peptides explained.

This article summarizes published testing and regulations for general information. It does not recommend any product.