Zinc (picolinate vs gluconate vs bisglycinate)
Summary
Zinc supplements come as gluconate, sulfate, acetate, citrate, picolinate, bisglycinate and oxide salts; labels list elemental zinc. Citrate and gluconate were absorbed similarly (about 61%) and oxide less (50%). Zinc lozenges shortened colds by about 2 days in low-certainty trials, without lowering cold risk. Adult intake above 40 mg/day (the UL) can lower copper status.
Key facts
- Gluconate, sulfate, acetate (most common), citrate, picolinate, bisglycinate, oxide; lozenges for colds[1]
- Citrate ≈ gluconate (about 61% absorbed); oxide lower (50%). Picolinate and bisglycinate advantages come from single small studies (grade D)[1][3][4][5]
- Cold duration with lozenges ↓ (B); cold risk ↔ (C); fasting blood sugar markers ↓ (B); progression of an age-related eye condition with a zinc + antioxidant formula ↓ (B)[2][6][7]
- 10–80 mg/day elemental zinc in the trials graded here; cold lozenge trials 45–276 mg/day of zinc gluconate for up to 3 weeks[3][7][2]
- RDA 11 mg (men), 8 mg (women); 11–12 mg in pregnancy and breastfeeding. UL 40 mg/day[1]
- Quinolone and tetracycline antibiotics, penicillamine, thiazide diuretics; iron supplements ≥25 mg taken at the same time[1]
- 1 Cochrane review, 1 meta-analysis, 1 large randomized trial and 3 small absorption studies[2][6][7][3][4][5]
- 7 graded human outcomes on this page
- October 9, 2026
How it works
EstablishedZinc is required for the catalytic activity of hundreds of enzymes and plays roles in immune function, protein and DNA synthesis, wound repair and cell signaling (established). For colds, researchers propose that zinc in lozenges acts locally in the mouth and throat on rhinovirus binding and inflammation (proposed).[1]
What the human research says
Human trials only, one row per outcome. The form column shows what each trial actually tested. Grades follow our evidence-grading policy.
At a glance: strongest evidence per outcome
| Outcome | Grade | Effect | Strongest evidence | Rows |
|---|---|---|---|---|
| Healthy aging | Grade B | Worsened | RCT · n = 3,640 · 2001 | 1 row |
| Metabolic | Grade B | Worsened | Meta-analysis · n = 1,700 · 2019 | 1 row |
| Immune | Grade B | Worsened | Systematic review · n = 972 · 2024 | 5 rows |
Every graded row
| Outcome | Effect | Grade | Best evidence | PMID |
|---|---|---|---|---|
| Progression of an age-related eye condition (AREDS formula) | Worsened | Grade B | RCT · n = 3,640 · 2001 Adults aged 55–80 with age-related macular degeneration or its early signs (AREDS) Form: zinc oxide, alone or with antioxidants (plus copper) · Dose: 80 mg zinc/day (with 2 mg copper), alone or with vitamins C and E and beta carotene · Duration: Average 6.3 years Antioxidants plus zinc lowered the odds of advanced AMD (OR 0.72; 99% CI 0.52-0.98). Zinc alone did not reach significance overall (OR 0.75; 99% CI 0.55-1.03) but did in the higher-risk subgroup. | 11594942 (opens PubMed)Source [7] |
| Fasting blood sugar and related markers | Worsened | Grade B | Meta-analysis · n = 1,700 · 2019 32 placebo-controlled interventions in 14 countries, including people with and without diabetes Form: various zinc salts · Dose: Varied across trials · Duration: Varied across trials Fasting glucose fell by 14.15 mg/dL and HbA1c by 0.55% versus control; 2-hour glucose, fasting insulin, insulin resistance and hs-CRP also fell. Effects on fasting glucose varied with diabetes status and the zinc formulation. | 31161192 (opens PubMed)Source [6] |
| Length of a cold when zinc is started after symptoms begin | Worsened | Grade B | Systematic review · n = 972 · 2024 8 treatment trials in people with the common cold Form: mostly zinc lozenges (gluconate or acetate); some syrups, tablets or nasal products · Dose: Zinc gluconate lozenges 45–276 mg/day across lozenge trials · Duration: 4.5–21 days Colds were 2.37 days shorter on average (MD -2.37; 95% CI -4.21 to -0.53), low-certainty evidence with very high heterogeneity (I² 97%). Non-serious side effects such as nausea were more common with zinc (RR 1.34). | 38719213 (opens PubMed)Source [2] |
| Chance of catching a cold with regular zinc | No effect | Grade C | Systematic review · n = 1,449 · 2024 9 prevention trials Form: zinc in various oral forms · Dose: Varied across trials · Duration: Up to 5–18 months of follow-up in some trials Little or no reduction in the risk of developing a cold (RR 0.93; 95% CI 0.85 to 1.01), low-certainty evidence. | 38719213 (opens PubMed)Source [2] |
| Zinc absorption: citrate vs gluconate vs oxide | Mixed | Grade D | Crossover RCT · n = 15 · 2014 Healthy young adults, fasting Form: zinc citrate vs zinc gluconate vs zinc oxide · Dose: 10 mg elemental zinc, single test doses · Duration: Single-dose isotope tests Median 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. | 24259556 (opens PubMed)Source [3] |
| Zinc status markers: picolinate vs citrate vs gluconate | Improved | Grade D | Crossover RCT · n = 15 · 1987 Healthy volunteers Form: zinc picolinate vs zinc citrate vs zinc gluconate vs placebo · Dose: 50 mg elemental zinc/day · Duration: 4 weeks per period Hair, 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. | 3630857 (opens PubMed)Source [4] |
| Zinc absorption: bisglycinate vs gluconate | Improved | Grade D | PK study · n = 12 · 2007 Healthy female volunteers Form: zinc bisglycinate vs zinc gluconate · Dose: 15 mg elemental zinc, single administration · Duration: Single doses with a 7-day washout Bisglycinate gave 43.4% higher oral bioavailability of zinc than gluconate, based on serum zinc levels. | 18271278 (opens PubMed)Source [5] |
Forms
| Form | Elemental % | Absorption (human data) | GI tolerance | Studied for |
|---|---|---|---|---|
| Zinc gluconate | 14.3%[9] | About 61% absorbed in young adults, similar to citrate and higher than oxide.[3][1] | Nausea and mouth irritation reported in lozenge trials.[2][8] | Cold lozenge trials; absorption comparisons |
| Zinc citrate | 34.2%[9] | 61.3% vs 60.9% for gluconate in a head-to-head isotope study (no difference).[3] | No form-specific tolerance data in our sources.[1] | Absorption comparison |
| Zinc picolinate | 21.1%[9] | One 1987 crossover trial (n=15) found higher hair, urine and red-cell zinc than citrate or gluconate; serum zinc did not differ.[4] | No form-specific tolerance data in our sources.[1] | Zinc status markers in healthy adults |
| Zinc bisglycinate (glycinate) | 30.6%[9] | 43.4% higher bioavailability than gluconate in a single-dose study of 12 women.[5] | Described as well tolerated in that study.[5] | Bioavailability |
| Zinc oxide | 80.3%[9] | 49.9% absorbed vs about 61% for citrate and gluconate; some people absorbed almost none.[3][1] | No form-specific tolerance data in our sources.[1] | AREDS eye-health formula |
| Zinc sulfate and zinc acetate | 22.7%[9] | No head-to-head human data in our sources.[1] | No form-specific tolerance data in our sources.[1] | Among the most common supplement forms; acetate used in some cold lozenges |
- Zinc oxide803 mg
- Zinc citrate342 mg
- Zinc bisglycinate (glycinate)306 mg
- Zinc sulfate and zinc acetate227 mg
- Zinc picolinate211 mg
- Zinc gluconate143 mg
Compound weight → elemental zinc
500 mg zinc gluconate ≈ 72 mg elemental zinc
Studied doses, daily needs and limits
Doses studied in human trials ranged from 10 to 80 mg/day of elemental zinc, from single test doses to about 6 years. The 80 mg/day eye-health trial was supervised, included copper, and is twice the adult UL of 40 mg/day.[3][4][7][2][1]
Intake reference: Adult RDA: 11 mg/day for men and 8 mg/day for women; 11 mg in pregnancy and 12 mg while breastfeeding (ages 19+). Adult UL: 40 mg/day from food and supplements.[1] The UL is based on zinc's adverse effect on copper status. It does not apply to people receiving zinc under medical care. NIH ODS fact sheet (updated January 6, 2026).
Recommended intake and upper limit by age and sex
| Age | Male | Female | Pregnancy | Lactation | Upper limit (UL) |
|---|---|---|---|---|---|
| 0–6 months (AI) | 2 mg | 2 mg | — | — | 4 mg |
| 7–12 months | 3 mg | 3 mg | — | — | 5 mg |
| 1–3 years | 3 mg | 3 mg | — | — | 7 mg |
| 4–8 years | 5 mg | 5 mg | — | — | 12 mg |
| 9–13 years | 8 mg | 8 mg | — | — | 23 mg |
| 14–18 years | 11 mg | 9 mg | 12 mg | 13 mg | 34 mg |
| 19+ years | 11 mg | 8 mg | 11 mg | 12 mg | 40 mg |
Dose math: how much compound supplies that much zinc
| Form (elemental %) | 8 mg zinc8 mg/day: adult RDA, women | 11 mg zinc11 mg/day: adult RDA, men | 40 mg zinc40 mg/day: adult upper limit (a ceiling, not a target) |
|---|---|---|---|
| Zinc gluconate (14.3%) | ≈ 60 mg compound | ≈ 80 mg compound | ≈ 280 mg compound |
| Zinc citrate (34.2%) | ≈ 20 mg compound | ≈ 30 mg compound | ≈ 120 mg compound |
| Zinc picolinate (21.1%) | ≈ 40 mg compound | ≈ 50 mg compound | ≈ 190 mg compound |
| Zinc bisglycinate (glycinate) (30.6%) | ≈ 30 mg compound | ≈ 40 mg compound | ≈ 130 mg compound |
| Zinc oxide (80.3%) | ≈ 10 mg compound | ≈ 10 mg compound | ≈ 50 mg compound |
| Zinc sulfate and zinc acetate (22.7%) | ≈ 40 mg compound | ≈ 50 mg compound | ≈ 180 mg compound |
Interactions
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
Medicines
- Quinolone and tetracycline antibioticsNIH fact sheetZinc and the antibiotic can bind in the gut and lower absorption of both. ODS notes that taking the antibiotic at least 2 hours before or 4–6 hours after zinc minimizes this.[1]
- PenicillamineNIH fact sheetZinc can reduce the absorption and action of penicillamine; ODS advises separating them by at least 1 hour.[1]
Medicines that can lower levels
- Thiazide diureticsNIH fact sheetIncrease urinary zinc excretion and lower serum zinc.[1]
Other supplements
- Iron supplements (25 mg or more)NIH fact sheetTaken at the same time as zinc, can reduce zinc absorption and plasma zinc. Iron in fortified foods does not meaningfully interfere.[1]
- CopperNIH fact sheetZinc at 50 mg/day or more for weeks can interfere with copper absorption and lead to low copper status.[1]
Who should be careful
- High intakes
- Above the 40 mg/day UL, zinc can cause nausea, vomiting, stomach upset and headaches. At 50 mg/day or more for weeks it can lower copper status, reduce immune function and lower HDL cholesterol. Overuse of zinc-containing denture creams has caused copper-deficiency nerve problems.[1]
- Groups more likely to be low
- People with gastrointestinal disorders or bariatric surgery, vegetarians and vegans, pregnant and breastfeeding women, older breastfed infants, children with sickle cell disease and people with alcohol use disorder are more likely to have low zinc status.[1]
- Medicines
- Some antibiotics, penicillamine and thiazide diuretics interact with zinc; ODS advises people on these medicines to discuss zinc with their clinician.[1]
- Before you start
- Talk to your pharmacist or clinician before adding this supplement, especially if you take prescription medicines, are pregnant or breastfeeding, or have a chronic health condition.[1]
Talk to your pharmacist or clinician before starting a supplement, especially if you take prescription medicines.
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Articles about Zinc (picolinate vs gluconate vs bisglycinate)
Plain-English answers to common questions, built on the evidence above.
Frequently asked questions
Which form of zinc is absorbed most?
Head-to-head human data are limited. In an isotope study, citrate and gluconate were absorbed about equally (61%) and oxide less (50%). Single small studies reported advantages for picolinate (1987, n=15) and bisglycinate (2007, n=12), but neither has been confirmed in larger trials.[3][4][5][1]
How much elemental zinc is in zinc gluconate?
About 14%: 50 mg of zinc gluconate supplies roughly 7 mg of zinc. Citrate is about 34%, bisglycinate about 31%, picolinate about 21% and oxide about 80% zinc by weight. US supplement labels list elemental zinc.[9][1]
Does zinc help with colds?
Zinc lozenges started after symptoms begin shortened colds by about 2 days on average in a 2024 Cochrane review, but the evidence is low certainty and trials varied widely. Regular zinc did not clearly lower the chance of catching a cold. Nausea and mouth irritation were more common with zinc.[2]
Can too much zinc cause problems?
Yes. The adult UL is 40 mg/day. Weeks at 50 mg/day or more can lower copper status, reduce immune function and lower HDL cholesterol.[1]
Should zinc and iron be separated?
ODS reports that iron supplements of 25 mg or more taken at the same time as zinc can reduce zinc absorption. Iron added to fortified foods does not meaningfully interfere.[1]
Sources
- [1]Zinc: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2026. fact-sheet
- [2]Zinc for prevention and treatment of the common cold.. Cochrane Database Syst Rev, 2024. systematic-review
- [3]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. crossover-RCT
- [4]Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans.. Agents Actions, 1987. crossover-RCT
- [5]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. PK-study
- [6]Zinc supplementation improves glycemic control for diabetes prevention and management: a systematic review and meta-analysis of randomized controlled trials.. Am J Clin Nutr, 2019. meta-analysis
- [7]A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8.. Arch Ophthalmol, 2001. RCT
- [8]Zinc for the prevention or treatment of acute viral respiratory tract infections in adults: a rapid systematic review and meta-analysis of randomised controlled trials.. BMJ Open, 2021. meta-analysis
- [9]Zinc gluconate, citrate, picolinate, bisglycinate, oxide and sulfate heptahydrate: molecular formulas and weights. PubChem, NCBI, 2026. database
What changed
- First draft. Every evidence-row PMID checked with NCBI E-utilities (esummary + efetch abstract) and re-read in an independent adversarial pass.
- Added intake table from the NIH ODS fact sheet (checked Oct 9 2026), cost-per-studied-dose method, labeled analysis derived from cited rows.