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Zinc Gluconate

Evidence Level
Moderate
4 Clinical Trials
3 Documented Benefits
3/5 Evidence Score

Zinc gluconate is zinc bound to gluconic acid, one of the forms most often found in supplements and the most common form in zinc lozenges. Zinc is an essential mineral needed by hundreds of enzymes and for normal immune function. In a crossover study in 12 men, zinc gluconate gave somewhat higher blood zinc levels than zinc oxide, though the gluconate dose was about 15 percent larger. Its best-known use is as a lozenge dissolved in the mouth at the first sign of a cold: an adult trial found symptoms cleared in a median 4.4 days versus 7.6 on placebo, but a trial in children found no difference, and a recent Cochrane review rated the evidence that zinc shortens colds as low certainty. Lozenges often cause bad taste and nausea. The adult upper limit is 40 mg of zinc a day, and the lozenge schedules exceed it, so they are meant for a few days only. Never use zinc in the nose.

Studied Dose Lozenges: 13.3 mg zinc every 2 hours while awake in the positive adult trial; pooled lozenge trials used 80 to 207 mg/day for a few days. Daily use: the adult upper limit is 40 mg/day.
Active Compound Zinc gluconate (zinc salt of gluconic acid); labels and doses refer to elemental zinc.

Benefits

Upper respiratory comfort: lozenges studied for symptom duration

In 100 adults starting lozenges within 24 hours of cold symptoms, symptoms cleared in a median 4.4 days versus 7.6 on placebo, but a 249-child trial found no difference. A pooled analysis of four gluconate lozenge trials found colds 28% shorter, while a recent review of all zinc forms rated the evidence low certainty.

Supported by Trial 1, Trial 3

Normal immune function

Zinc is an essential mineral that plays a role in immune function, and it is needed by hundreds of enzymes and for protein and DNA synthesis and wound healing. Most people in the United States get enough from food. Taking 50 mg or more a day for weeks can reduce immune function and copper absorption.

Supported by Trial 1, Trial 2

Absorption compared with other zinc forms

In a 14-day crossover study in 12 healthy men, zinc gluconate gave an 18% higher peak and 8% higher total blood zinc level than zinc oxide, though the gluconate group got about 15 percent more zinc. In a tracer study in 15 adults, about 61% of the zinc was absorbed from gluconate and from citrate, versus 50% from oxide. These are absorption measures, not health outcomes.

Supported by Trial 1, Trial 2

Mechanism of action

1

Contact with the mouth and throat (proposed)

Zinc lozenges are dissolved slowly in the mouth, and the gluconate trials that reported shorter colds used this route. The authors of the positive adult trial stated that how zinc acts on cold symptoms remains unknown.

2

Enzyme and immune roles

Zinc is required for the activity of hundreds of enzymes and takes part in immune function, protein and DNA synthesis, wound healing and cell division. Zinc gluconate supplies the same zinc as other forms once absorbed.

Clinical trials

1
Zinc gluconate lozenges in adults with a new cold
PubMed

Randomized, double-blind, placebo-controlled trial of lozenges with 13.3 mg zinc from zinc gluconate every 2 hours while awake, started within 24 hours of symptoms (Mossad et al. 1996, Ann Intern Med).

100 employees of the Cleveland Clinic (50 zinc, 50 placebo).

Symptoms cleared in a median 4.4 days on zinc versus 7.6 days on placebo (p < 0.001), with fewer days of cough, headache, hoarseness, nasal congestion and sore throat. Side effects were more common on zinc (90% vs 62%), including bad taste (80% vs 30%) and nausea (20% vs 4%).

2
Zinc gluconate lozenges in children and teenagers: no difference
PubMed

Randomized, double-masked, placebo-controlled trial of 10 mg zinc gluconate glycine lozenges taken 5 or 6 times a day, started within 24 hours of symptoms (Macknin et al. 1998, JAMA).

249 students in grades 1 to 12 in two Cleveland-area school districts.

Time to resolution of cold symptoms did not differ (median 9 days in both groups, p = 0.71), and none of the 9 symptoms improved. Bad taste (60.2% vs 37.9%) and nausea (29.3% vs 16.1%) were more common on zinc.

3
Pooled analysis of zinc acetate and zinc gluconate lozenges
PubMed

Meta-analysis of seven placebo-controlled lozenge trials using more than 75 mg zinc a day (Hemila 2017, JRSM Open).

575 people with naturally acquired colds.

Colds were 33% shorter overall (95% CI 21% to 45%): 40% in three acetate trials and 28% in four gluconate trials, a difference between the salts that was not significant. Doses above 100 mg a day did not work better.

4
Cochrane review of zinc for colds
PubMed

Cochrane systematic review of 34 placebo-controlled trials (8,526 participants) of any zinc form for preventing or treating colds (Nault et al. 2024, Cochrane Database Syst Rev).

Children and adults; gluconate lozenges were the most common form in the treatment trials.

Used as treatment, zinc may shorten colds by about 2.4 days (low-certainty evidence, high heterogeneity) and probably raises the risk of non-serious side effects (RR 1.34). Zinc may have little or no effect on preventing colds.

Side effects and drug interactions

Common Potential side effects

Lozenges: bad taste and nausea are common. In the adult trial, 80% of the zinc group reported bad taste and 20% nausea; in the children's trial, mouth or throat discomfort and diarrhea were also more frequent on zinc.
Too much zinc can cause nausea, dizziness, headaches, stomach upset, vomiting and loss of appetite. Taking 50 mg or more a day for weeks can reduce copper absorption and immune function and lower HDL cholesterol. The adult upper limit is 40 mg a day (NIH ODS).
The lozenge schedules used in cold trials provide 50 mg or more of zinc a day (more than 75 mg in the pooled adult trials), above the 40 mg upper limit, so keep them to the few days of a cold.
Loss of smell: zinc gluconate nasal gel has caused loss of smell, reported in a series of 17 patients. Do not use zinc products in the nose.

Important Drug interactions

Quinolone and tetracycline antibiotics: zinc may interact with them (NIH ODS). Ask your pharmacist how far apart to take them.
Penicillamine: zinc may interact with it (NIH ODS).
Some diuretics increase zinc loss in the urine (NIH ODS).
Iron: taking 25 mg or more of supplemental iron at the same time as zinc can reduce zinc absorption (NIH ODS).

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Frequently asked questions about Zinc Gluconate

What is zinc gluconate?

Zinc gluconate is zinc bound to gluconic acid. It is one of the most common zinc forms in supplements and is the form most often used in cold lozenges.

Is zinc gluconate good for colds?

Results are mixed. Lozenges started within 24 hours shortened symptoms in an adult trial but not in a trial in children, and a 2024 Cochrane review rated the evidence that zinc shortens colds as low certainty. The lozenge must dissolve slowly in the mouth, and bad taste and nausea are common.

How much zinc gluconate should I take?

Doses are given as elemental zinc. The adult upper limit for daily use is 40 mg. The lozenge schedules in cold trials gave 50 mg or more a day, and more than 75 mg in the pooled adult trials, so they are meant for a few days only.

When should I take zinc gluconate?

Do not take it at the same time as an iron supplement of 25 mg or more, which can reduce zinc absorption. If you take a quinolone or tetracycline antibiotic, ask your pharmacist how to space them. For cold lozenges, let them dissolve slowly in the mouth.

What is Zinc Gluconate used for?

Zinc Gluconate is researched primarily for Immune Support and Respiratory Health. In 100 adults starting lozenges within 24 hours of cold symptoms, symptoms cleared in a median 4.4 days versus 7.6 on placebo, but a 249-child trial found no difference.

Is Zinc Gluconate safe, and does it have side effects?

Side effects and cautions reported for Zinc Gluconate include: Lozenges: bad taste and nausea are common. In the adult trial, 80% of the zinc group reported bad taste and 20% nausea; in the children's trial, mouth or throat discomfort and diarrhea were also more frequent on zinc. It may also interact with some medications. Zinc Gluconate is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Zinc Gluconate interact with any medications?

Possible interactions include: Quinolone and tetracycline antibiotics: zinc may interact with them (NIH ODS). Ask your pharmacist how far apart to take them. Penicillamine: zinc may interact with it (NIH ODS). If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Zinc Gluconate?

NutraSmarts rates the evidence for Zinc Gluconate as Moderate (3 out of 5). It is backed by 4 study summaries and 8 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(8 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Mossad SB, Macknin ML, Medendorp SV, Mason P. Zinc gluconate lozenges for treating the common cold. A randomized, double-blind, placebo-controlled study. Ann Intern Med. 1996;125(2):81-8. doi: 10.7326/0003-4819-125-2-199607150-00001.PubMedUsed to support: Randomized, double-blind, placebo-controlled trial in 100 Cleveland Clinic employees with cold symptoms for less than 24 hours. Lozenges with 13.3 mg zinc from zinc gluconate every 2 hours while awake cut the median time to symptom resolution to 4.4 days versus 7.6 on placebo (p < 0.001). Side effects (90% vs 62%), bad taste (80% vs 30%) and nausea (20% vs 4%) were more common on zinc.
  2. Macknin ML, Piedmonte M, Calendine C, Janosky J, Wald E. Zinc gluconate lozenges for treating the common cold in children: a randomized controlled trial. JAMA. 1998;279(24):1962-7. doi: 10.1001/jama.279.24.1962.PubMedUsed to support: Randomized, double-masked, placebo-controlled trial in 249 students in grades 1 to 12 starting 10 mg zinc gluconate glycine lozenges 5 or 6 times a day within 24 hours of cold symptoms. Time to resolution did not differ (median 9 days in both groups, p = 0.71). Bad taste, nausea, mouth or throat discomfort and diarrhea were more common on zinc.
  3. Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. 2017;8(5):2054270417694291. doi: 10.1177/2054270417694291.PubMedUsed to support: Meta-analysis of seven placebo-controlled lozenge trials (575 participants) using more than 75 mg zinc a day. Colds were 33% shorter overall, 40% in three zinc acetate trials and 28% in four zinc gluconate trials; the difference between salts (12 percentage points, 95% CI -12 to +36) was not significant, and doses of 192 to 207 mg a day worked no better than 80 to 92 mg.
  4. Nault D, Machingo TA, Shipper AG, Antiporta DA, Hamel C, Nourouzpour S, Konstantinidis M, Phillips E, Lipski EA, Wieland LS. Zinc for prevention and treatment of the common cold. Cochrane Database Syst Rev. 2024;5(5):CD014914. doi: 10.1002/14651858.CD014914.pub2.PubMedUsed to support: Cochrane review of 34 placebo-controlled trials (8,526 participants) of zinc for colds. As treatment, zinc may shorten colds (mean difference -2.37 days, low-certainty evidence, high heterogeneity) and probably increases non-serious adverse events (RR 1.34, moderate certainty). As prevention, it may have little or no effect. Gluconate lozenges were the most common treatment form.
  5. Siepmann M, Spank S, Kluge A, Schappach A, Kirch W. The pharmacokinetics of zinc from zinc gluconate: a comparison with zinc oxide in healthy men. Int J Clin Pharmacol Ther. 2005;43(12):562-5. doi: 10.5414/cpp43562.PubMedUsed to support: Randomized crossover study in 12 healthy men aged 21 to 31 taking 20 mg zinc as zinc gluconate or 17.4 mg as zinc oxide daily for 14 days each. Peak plasma zinc was 18.3% higher and 24-hour exposure 8.1% higher with gluconate (both p < 0.05).
  6. Wegmüller R, Tay F, Zeder C, Brnic M, Hurrell RF. 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;144(2):132-6. doi: 10.3945/jn.113.181487.PubMedUsed to support: Randomized, double-masked, three-way crossover isotope study in 15 healthy adults given 10 mg zinc without food. Median fractional absorption was 61.3% from zinc citrate and 60.9% from zinc gluconate, not different from each other, and 49.9% from zinc oxide, which was significantly lower (P < 0.01).
  7. Alexander TH, Davidson TM. Intranasal zinc and anosmia: the zinc-induced anosmia syndrome. Laryngoscope. 2006;116(2):217-20. doi: 10.1097/01.mlg.0000191549.17796.13.PubMedUsed to support: Case series of 17 patients who lost or had reduced sense of smell after using an intranasal zinc gluconate gel sold for colds. All reported a burning sensation after sniffing the gel, followed by smell loss within 48 hours.
  8. NIH Office of Dietary Supplements Zinc: Fact Sheet for Health Professionals National Institutes of Health. ;Web page (not PubMed-indexed)..SourceUsed to support: Not PubMed-indexed: US government fact sheet. Zinc is needed by hundreds of enzymes and plays a role in immune function, protein and DNA synthesis and wound healing. Zinc gluconate is a common supplement form. Trials of zinc for colds have mixed results. Excess zinc causes nausea, dizziness, headaches and stomach upset; 50 mg or more a day for weeks can inhibit copper absorption and reduce immune function; the adult upper limit is 40 mg. Zinc may interact with quinolone and tetracycline antibiotics and penicillamine, some diuretics increase zinc loss, and iron of 25 mg or more taken at the same time can reduce zinc absorption.