Protocols › Zinc

Zinc for colds

Goal: What trials of zinc lozenges used to make colds shorter.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 10 Nov 2026
Dose

Zinc gluconate lozenges gave 45 to 276 mg of zinc a day in the trials of a 2024 Cochrane review.[1] An earlier review found an effect only with more than 75 mg a day.[2]

Form

Lozenges of zinc gluconate, zinc acetate or zinc orotate. Gluconate lozenges were the most common.[1]

When to take

In one trial, adults started within 24 hours of the first symptoms and took one lozenge every 2 to 3 waking hours.[2]

How long

4.5 to 21 days for gluconate lozenges.[1]

What studies found

In 8 trials with 972 people, colds lasted 2.37 days less with zinc, with low certainty. Zinc did not clearly prevent colds.[1] A 2012 review found the effect in adults (2.63 days), not in children.[3]

Ask a doctor first

These doses are above the US upper limit for adults of 40 mg a day. Taken for weeks, 50 mg or more a day can lower copper absorption.[2] In a 2012 review of cold trials, zinc taken by mouth caused more bad taste and nausea than placebo.[3] Zinc and quinolone or tetracycline antibiotics can block each other's absorption.[2]

Ask a doctor or pharmacist first if you take antibiotics, penicillamine or a thiazide diuretic.[2]

References

  1. Zinc for prevention and treatment of the common cold. Nault D, Machingo TA, Shipper AG, Antiporta DA, Hamel C, Nourouzpour S, et al. Cochrane Database Syst Rev, 2024. PMID 38719213
  2. Zinc: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  3. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. Science M, Johnstone J, Roth DE, Guyatt G, Loeb M CMAJ, 2012. PMID 22566526