The most bioavailable form of copper supplement — chelated to glycine for better absorption and gentler digestion. This guide covers everything you need to know.
Copper bisglycinate is a chelated form of copper used in dietary supplements, in which one copper ion is bonded to two molecules of the amino acid glycine. It is one of several copper compounds available on the supplement market — alongside copper gluconate, copper citrate, copper sulfate, and others — and is widely marketed as the most bioavailable form. This guide examines that claim in detail, sets out what the evidence actually shows, and provides a practical reference on dose, timing, safety, deficiency, and how copper bisglycinate compares to other copper forms.
This is an encyclopedic reference, not a sales page. Every factual claim is sourced to a public document — the NIH Office of Dietary Supplements, the Institute of Medicine’s Dietary Reference Intakes, peer-reviewed journals, and government toxicology profiles. Where the evidence is limited or animal-only, this guide says so plainly.
Copper bisglycinate is a copper-amino-acid chelate. The compound consists of a bivalent copper ion (Cu²⁺) bonded to two molecules of glycine, the simplest amino acid. The bond is a coordinate covalent bond formed at both the carboxyl group and the α-amino group of each glycine molecule, producing a stable ring-like structure around the central copper ion.
The chemical formula is Cu(C₂H₄NO₂)₂. The compound is sometimes also written as copper(II) bisglycinate, copper diglycinate, or — when commercial branding is involved — by the trade name TRAACS® Copper Bisglycinate Chelate, a patented form manufactured by Balchem (formerly Albion Laboratories) and used by many supplement brands including Thorne.
Copper itself is an essential trace mineral. Adults require small but regular amounts to maintain dozens of copper-dependent enzymes — including cytochrome c oxidase in the mitochondrial electron transport chain, superoxide dismutase in antioxidant defense, lysyl oxidase in collagen and elastin crosslinking, and ceruloplasmin in iron metabolism. The recommended dietary allowance set by the Institute of Medicine is 900 micrograms per day for adults.
In inorganic copper supplements such as copper sulfate or copper oxide, the copper ion is paired with a non-organic counterion. Once such compounds enter the digestive tract, the copper ion dissociates and becomes vulnerable to competing reactions: it can bind with dietary phytates, oxalates, and tannins; it can compete with zinc and iron at intestinal transporters; and it can participate in unwanted oxidation reactions that may irritate the gastrointestinal lining.
Chelation is meant to address these problems. Bonding copper to two glycine molecules — a 1:2 metal-to-ligand ratio — produces a stable ring structure that shields the copper ion from these interactions as it transits the stomach and reaches the small intestine. The theoretical result is improved tolerability and improved absorption. The first part of that claim (tolerability) is reasonably well supported in practice. The second part (improved absorption) is more nuanced than most marketing copy suggests.
Glycine bonding protects the copper from reacting with other dietary inhibitors in the stomach. This allows it to be absorbed directly into the bloodstream, making it far more effective than other forms.
Unlike elemental copper or copper sulfate, which can cause stomach upset, copper bisglycinate is known for being exceptionally gentle on the digestive system.
Most supplement-industry copy describes copper bisglycinate as “the most bioavailable form” of copper. This is a defensible directional claim but a poorly substantiated quantitative one. The published research breaks down into three categories.
The strongest peer-reviewed bioavailability data on copper glycinate comes from ruminant nutrition research. A 2007 study published in the Journal of Animal Science (Hansen et al.) found that copper bisglycinate showed approximately 140–150% relative bioavailability compared to copper sulfate in steers fed diets high in antagonistic sulfur and molybdenum, measured by plasma copper, liver copper, and ceruloplasmin.
A 2025 review in Nutrients examined copper bisglycinate’s behavior in cell culture and discussed its mechanism. The authors confirm that copper bisglycinate is widely assumed to have higher bioavailability than copper sulfate because of its chelated structure, but they note that detailed bioavailability work in humans is sparse.
Human randomized controlled trials specifically comparing copper bisglycinate against other copper forms with clinical endpoints are limited. A 2020 review from the University of Virginia GI Nutrition program noted that chelated copper products “claim to be more bioavailable, passing easily through intestinal tract and directly into bloodstream” but added the caveat: “no scientific proof available” in the form of definitive human bioavailability comparisons.
Copper bisglycinate is plausibly better absorbed than inorganic copper forms, and it is consistently better tolerated. The case for superior absorption rests primarily on animal data and mechanistic reasoning. Human trials comparing it head-to-head against copper sulfate, copper gluconate, or copper citrate are limited. If you encounter a source that asserts “three times more bioavailable” or a similar specific multiplier in humans, it is overreaching what the published evidence supports.
The chemical formula is Cu(C₂H₄NO₂)₂. The compound is sometimes also written as copper(II) bisglycinate, copper diglycinate, or — when commercial branding is involved — by the trade name TRAACS® Copper Bisglycinate Chelate, a patented form manufactured by Balchem (formerly Albion Laboratories) and used by many supplement brands including Thorne.
Copper itself is an essential trace mineral. Adults require small but regular amounts to maintain dozens of copper-dependent enzymes — including cytochrome c oxidase in the mitochondrial electron transport chain, superoxide dismutase in antioxidant defense, lysyl oxidase in collagen and elastin crosslinking, and ceruloplasmin in iron metabolism. The recommended dietary allowance set by the Institute of Medicine is 900 micrograms per day for adults.
Several copper compounds are used in supplements. Each has different absorption characteristics, tolerability, and historical use.
| Form | Type | Tolerability | Notes |
|---|---|---|---|
| Copper bisglycinate | Chelated (amino acid) | Excellent | 1:2 copper-to-glycine ratio. Plausibly highest bioavailability based on animal data. Best for sensitive stomachs. |
| Copper glycinate | Chelated (amino acid) | Good | Sometimes used interchangeably with copper bisglycinate. May refer to a 1:1 ratio compound or be used loosely as a synonym. |
| Copper citrate | Organic salt | Moderate | Widely used in supplements. Reasonable absorption. Less protected against dietary inhibitors than chelated forms. |
| Copper gluconate | Organic salt | Moderate | Common in older supplement formulations. Adequate absorption. Inexpensive. |
| Copper sulfate | Inorganic salt | Poor at supplemental doses | Cheap and chemically reactive. Can cause GI irritation. More common in agricultural and industrial applications than human supplements. |
| Copper oxide | Inorganic | Poor | Very low bioavailability. Sometimes added to multivitamins as a cost-cutting measure. Avoid. |
| Elemental copper | Pure metal | Poor | Not used in human supplementation. Listed for completeness. |
Copper is a cofactor for a small but disproportionately important group of enzymes. It participates in dozens of physiological processes, and adequate copper status is required for normal function across multiple organ systems. The following are the most extensively documented roles.
Copper is required for cytochrome c oxidase, the terminal enzyme in the mitochondrial electron transport chain. Without adequate copper, mitochondrial ATP production is impaired. This is the biochemical basis for the fatigue commonly reported in copper deficiency.
Copper is part of copper-zinc superoxide dismutase (Cu/Zn SOD), one of the body’s primary enzymatic defenses against reactive oxygen species. SOD catalyzes the conversion of superoxide radicals into hydrogen peroxide, which is then further reduced by other enzymes.
Ceruloplasmin — a copper-dependent enzyme synthesized in the liver — is essential for iron mobilization. It oxidizes ferrous iron (Fe²⁺) to ferric iron (Fe³⁺), the form that can bind to transferrin and be transported through the bloodstream. Copper deficiency therefore presents in many cases as a functional iron deficiency anemia that does not respond to iron supplementation.
Lysyl oxidase, a copper-dependent enzyme, catalyzes the cross-linking of collagen and elastin fibers. These crosslinks are essential for the tensile strength of skin, the elasticity of blood vessels, and the integrity of bone matrix.
Tyrosinase — the enzyme that catalyzes the rate-limiting step of melanin synthesis — is copper-dependent. Premature graying of hair is a recognized sign of copper deficiency, and pale skin patches sometimes accompany deficiency.
Several copper-dependent enzymes participate in neurotransmitter synthesis, most notably dopamine β-hydroxylase, which converts dopamine to norepinephrine. Severe copper deficiency can produce ataxia, myelopathy, and neuropathy.
| Population | Daily intake |
|---|---|
| Adults 19+ years (men and women) | 900 mcg (0.9 mg) |
| Pregnant adults | 1,000 mcg (1.0 mg) |
| Lactating adults | 1,300 mcg (1.3 mg) |
| Tolerable Upper Intake Level (adults) | 10,000 mcg (10 mg) |
The Institute of Medicine’s Recommended Dietary Allowance (RDA) for copper, established in 2001 and reaffirmed by the NIH Office of Dietary Supplements, is as follows for adults.
Typical U.S. dietary intake of copper from food alone is approximately 1,400 mcg/day for men and 1,100 mcg/day for women, according to NHANES data referenced by the NIH ODS. This means most adults meet the RDA from food. Supplementation is most warranted when (a) intake is inadequate, (b) high-dose zinc supplementation is creating a competitive deficiency, or (c) absorption is impaired due to bariatric surgery or chronic GI conditions.
Most copper bisglycinate supplements supply 2 mg of elemental copper per capsule. This is above the 900 mcg RDA but well below the 10,000 mcg upper limit.
Severe copper deficiency is uncommon in healthy adults eating a varied diet, according to the NIH ODS. Suboptimal copper status is more common and may be present in people with high zinc intake, bariatric surgery, malabsorption syndromes, or longstanding restrictive diets. Established clinical signs include:
At recommended supplemental doses — typically 1–5 mg per day — copper bisglycinate is generally well tolerated. The chelated form is consistently described as gentler on the GI tract than copper sulfate, which can cause nausea and stomach irritation at supplemental doses. Chronic dietary copper toxicity in healthy adults is not considered a significant public health concern by the NIH or the ATSDR.
At very high acute doses (well above the 10 mg upper limit), copper supplementation can produce nausea, vomiting, abdominal pain, and diarrhea. The 10 mg upper limit set by the Institute of Medicine is based on protection against hepatic injury.
Copper bisglycinate is generally taken once daily. It is well tolerated on an empty stomach because of the chelated form, but many people prefer to take it with food, particularly a meal containing protein. Avoid taking it simultaneously with high-dose iron or zinc supplements; if you take all three, spacing them apart by several hours may help avoid competition for absorption.
Copper and zinc are reciprocal at the level of intestinal absorption. High zinc intake — particularly the 50–100 mg/day doses common in immune-support supplements — induces metallothionein in enterocytes. Metallothionein has higher binding affinity for copper than for zinc, so it preferentially traps copper, which is then lost when enterocytes are sloughed off. Over months, this can produce clinically significant copper deficiency.
This mechanism is well established and has been documented in clinical case reports and reviews. The British Journal of Clinical Pharmacology published a 2023 review (Duncan et al.) finding that zinc-induced copper deficiency is frequently missed and can produce irreversible neurological complications. If you supplement zinc above the RDA (8–11 mg/day) for an extended period, copper supplementation is reasonable to consider.
The two terms are often used interchangeably in the supplement industry. “Bisglycinate” specifies the 1:2 copper-to-glycine ratio. “Copper glycinate” may refer to the same compound or to a 1:1 ratio compound, depending on the manufacturer. Most products labeled “copper glycinate” are functionally copper bisglycinate.
Copper bisglycinate is more consistently tolerated and is plausibly better absorbed, particularly in the presence of dietary inhibitors. Copper sulfate is inorganic, dissociates in the stomach, and can cause GI irritation at supplemental doses. Most supplement companies have moved away from copper sulfate for these reasons.
Any time of day works. Many people take it with breakfast or another protein-containing meal. The chelated form does not require food for tolerability, but food can help if you have a sensitive stomach. Avoid simultaneous high-dose iron or zinc.
There is no single answer. Mild functional insufficiency may resolve in weeks. Established deficiency with hematological signs typically improves over 2–6 months of consistent supplementation. Neurological signs from severe, prolonged deficiency may only partially reverse — a strong argument for early correction.