Evidence explainerZinc (picolinate vs gluconate vs bisglycinate)

Zinc Picolinate, Citrate or Gluconate? The Absorption Data, and Why More Zinc Can Cost You Copper

Zinc labels compete on form and milligrams. The head-to-head data is thin, the elemental math matters more than the salt, and the real risk is quietly taking too much.

By Kymata Health editorial teamPublished October 9, 2026Last reviewed October 9, 2026

Medical review pending. Written by our editorial team from the studies cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • In an isotope study, zinc citrate and gluconate were absorbed about equally (61.3% vs 60.9%), and oxide less (49.9%) [1].
  • Advantages for picolinate (1987, 15 people) and bisglycinate (2007, 12 women) come from single small studies [2][3].
  • Labels list elemental zinc: gluconate is about 14% zinc, citrate about 34%, oxide about 80% [4][5].
  • The adult upper limit is 40 mg/day; weeks at 50 mg/day or more can lower copper status [5].

The evidence, graded

Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.

  • Grade DMixedZinc absorption: citrate vs gluconate vs oxideZinc (picolinate vs gluconate vs bisglycinate) · Crossover RCT · n=15 · 2014 · PMID 24259556Median fractional absorption was 61.3% from citrate and 60.9% from gluconate (no difference), but 49.9% from oxide (significantly lower). Three participants absorbed little or no zinc from oxide.
  • Grade DImprovedZinc status markers: picolinate vs citrate vs gluconateZinc (picolinate vs gluconate vs bisglycinate) · Crossover RCT · n=15 · 1987 · PMID 3630857Hair, urine and red-blood-cell zinc rose significantly only with picolinate; none changed with citrate, gluconate or placebo. Serum zinc did not rise significantly with any form.
  • Grade DImprovedZinc absorption: bisglycinate vs gluconateZinc (picolinate vs gluconate vs bisglycinate) · PK study · n=12 · 2007 · PMID 18271278Bisglycinate gave 43.4% higher oral bioavailability of zinc than gluconate, based on serum zinc levels.

What the absorption studies show

The best comparison used isotope tracers in 15 fasting young adults given 10 mg of zinc [1]. Median absorption was 61.3% from citrate, 60.9% from gluconate and 49.9% from oxide, and three people absorbed little or none from oxide [1].

A 1987 crossover trial in 15 volunteers found that hair, urine and red-cell zinc rose only with picolinate at 50 mg/day, though serum zinc did not rise significantly with any form [2]. A 2007 single-dose study in 12 women reported 43.4% higher bioavailability from bisglycinate than gluconate [3]. Neither result has been confirmed in larger trials, so we grade both D.

The number on the label

US labels list elemental zinc, the zinc itself [5]. By weight, zinc gluconate is about 14% zinc, picolinate about 21%, bisglycinate about 31%, citrate about 34% and oxide about 80% [4]. So 50 mg of zinc gluconate supplies roughly 7 mg of zinc [4].

How much is enough, and how much is too much

The adult RDA is 11 mg/day for men and 8 mg/day for women [5]. The upper limit is 40 mg/day from food and supplements, set because of zinc’s effect on copper [5]. Above it, nausea, vomiting, stomach upset and headaches become more likely, and 50 mg/day or more for weeks can lower copper status, reduce immune function and lower HDL cholesterol [5].

Overuse of zinc-containing denture creams has caused copper-deficiency nerve problems, a reminder that zinc adds up from unexpected places [5].

Medicines and other supplements

Iron absorption has its own quirks; see iron pills without the stomach upset. For colds specifically, read zinc for colds.

  • Quinolone and tetracycline antibiotics: take the antibiotic at least 2 hours before or 4 to 6 hours after zinc [5].
  • Penicillamine: separate by at least 1 hour [5].
  • Thiazide diuretics increase zinc loss in urine [5].
  • Iron supplements of 25 mg or more taken at the same time can reduce zinc absorption [5].

Keep reading

Full monographs

Related articles

Browse the full Supplement & Nutrient Encyclopedia or all supplement articles.

References

  1. [1]Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. J Nutr, 2014. PMID 24259556
  2. [2]Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents Actions, 1987. PMID 3630857
  3. [3]A bioavailability study comparing two oral formulations containing zinc (Zn bis-glycinate vs. Zn gluconate) after a single administration to twelve healthy female volunteers. Int J Vitam Nutr Res, 2007. PMID 18271278
  4. [4]Zinc gluconate, citrate, picolinate, bisglycinate, oxide and sulfate heptahydrate: molecular formulas and weights. PubChem, NCBI, 2026.
  5. [5]Zinc: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2026.

Zinc (picolinate vs gluconate vs bisglycinate) and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. This page has no product or affiliate links.

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