How much can zinc actually shorten a cold?
The best evidence shows that zinc can cut the length of a cold by roughly 2 days, but only if you start taking it soon after symptoms begin. A 2024 Cochrane review — the largest and most rigorous analysis of the topic, pooling 19 treatment trials with nearly 1,000 participants — found that people who took zinc had colds that were, on average, 2.37 days shorter than those on placebo [1]. That is a meaningful difference for most people. A separate 2013 Cochrane review of 16 trials reported a smaller but still significant reduction of about 1 day [4]. The variation likely comes from differences in zinc dose and formulation across studies.
Does zinc prevent colds or make symptoms less severe?
No — zinc does not appear to prevent colds, and its effect on symptom severity is weak at best. The 2024 Cochrane review looked at 9 prevention trials involving over 1,400 people and found that zinc did not significantly reduce the risk of catching a cold [1]. When it comes to severity, the same review found that zinc had little or no effect on how bad symptoms felt [1]. A 2025 study in school-aged children did report lower severity scores in the zinc group, but that was a single small trial [3]. Overall, the strongest evidence says zinc does not make you feel much better while you are sick — it just helps you get over it faster.
What is the catch? Side effects and formulation matter
The main downside is that zinc often causes unpleasant side effects, and not all formulations work equally well. The 2024 Cochrane review found that people taking zinc for a cold were about 34% more likely to report non-serious side effects like bad taste, nausea, or stomach cramps [1]. A 2021 trial of zinc acetate lozenges found that 63% of participants reported some adverse effect, compared to only 31% in the placebo group [5]. That same trial also found no benefit from the lozenges, possibly because the dose (13 mg zinc, 6 times per day) was lower than the 75 mg/day or more that earlier research suggests is needed [4][5]. So if you try zinc, you need a high enough dose — typically at least 75 mg/day of elemental zinc from lozenges — and you have to tolerate the taste.
About These Sources
This answer is built on 5 peer-reviewed studies — published from 2013 to 2025, 2 from 2024 or later, 2 in Q1 journals — selected as the most relevant from 5 studies that passed quality screening, drawn from 40 papers retrieved from a database of over 500 million.
Sources used in this answer
Zinc for prevention and treatment of the common cold
In a 2024 Cochrane review of 34 randomized controlled trials (19 treatment, 15 prevention) involving 8,526 participants, zinc shortened cold duration by about 2.37 days when used for treatment, but did not prevent colds and increased non-serious side effects by 34%.
Vitamin C reduces the severity of common colds: a meta-analysis
A 2023 meta-analysis of 10 trials found that vitamin C reduced cold severity by 15%, but this paper is about vitamin C, not zinc, and is not directly relevant to the question.
Efficacy of Zinc Supplementation in Reducing the Severity and Duration ofCommon Cold in School-Aged Children: A Prospective Study
A 2025 prospective study of 120 school-aged children found that 15 mg/day of zinc sulfate reduced cold duration from 6.1 to 4.2 days and lowered recurrence rates from 30% to 15%.
Zinc for the common cold.
A 2013 Cochrane review of 16 therapeutic trials (1,387 participants) found that zinc shortened cold duration by about 1 day and reduced the odds of still being symptomatic after 7 days, but increased side effects like bad taste and nausea.
Zinc acetate lozenges for the treatment of the common cold: a randomised controlled trial.
A 2021 randomized controlled trial of 87 adults in Finland found that zinc acetate lozenges (13 mg, 6 times/day for 5 days) did not speed recovery from the common cold, and 63% of zinc users reported adverse effects.