Supplement analysis backed by scientific evidence · PT

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Moderate evidenceImmunity

Zinc Gluconate

The most common zinc salt in cold lozenges. It shortens colds when the total daily zinc dose is high enough and treatment starts early, though the trial record is inconsistent and the lozenges taste unpleasant.

Evidence last reviewed: August 2026

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What the science says

  • Shorter colds at adequate zinc doses Moderate evidence

    A meta-analysis comparing zinc acetate and zinc gluconate lozenges found that both salts shortened colds when total daily zinc was around 80–90 mg, with no significant difference between the two salts. Low-dose gluconate lozenges did not show a benefit, which explains much of the inconsistency in older trials.

  • Earlier meta-analyses were mixed Moderate evidence

    A 1997 meta-analysis of zinc salt lozenges found the evidence conflicting and dose-dependent. A 2013 Cochrane review reported reduced cold duration but was later withdrawn over methodological concerns, so it should not be cited as current support.

  • Prevention is not established Limited evidence

    The trials tested lozenges started within about a day of symptom onset as treatment. Taking zinc gluconate continuously to avoid catching colds has much weaker support and carries the risk of copper depletion.

Dosage & safety

Studied doseLozenges providing 13–23 mg of elemental zinc, dissolved slowly in the mouth every two to three hours while awake, for a total of roughly 75–100 mg per day. Start within 24 hours of the first symptoms and stop after about a week.
SafetyBad taste, nausea and mouth irritation are common and cause many people to stop. Doses of this size are safe for a few days but not for continuous use — sustained high zinc intake causes copper deficiency, anaemia and neurological problems. Zinc reduces absorption of tetracycline and quinolone antibiotics. Never use intranasal zinc products, which have caused permanent loss of smell.

Scientific references

Where to buy

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