Zinc for Colds: What to Know Before Taking It

Quick answer

Zinc is an essential mineral the immune system needs. Zinc lozenges started within 24 hours of the first cold symptoms may shorten a cold by about a day or two, according to some trials. However, the latest Cochrane review (2024) found the evidence to be low certainty overall, and side effects such as a bad taste and nausea were common.

Zinc does not prevent colds in well-nourished people, and taking high doses for weeks can cause copper deficiency. Zinc nasal sprays and gels have been linked to permanent loss of smell and should never be used.

Why zinc might help

Zinc is needed for normal immune cell function. In the lab, zinc ions can stop the most common cold viruses (rhinoviruses) from multiplying and from attaching to cells in the nose and throat. The theory behind lozenges is that slowly dissolving zinc in the mouth releases zinc ions directly where the virus is active.

What the research says

• Earlier reviews found that zinc lozenges started within 24 hours reduced the length of colds, with some analyses suggesting a reduction of about a third in adults.
• The 2024 Cochrane review, which included over 30 trials, concluded that zinc may shorten colds slightly but that the evidence was of low certainty, trial designs varied widely, and the benefit was uncertain. Zinc did not clearly prevent colds.
• Formulation matters. Lozenges using zinc acetate or zinc gluconate with no citric acid or other ingredients that bind zinc seemed to work better in some analyses. Many commercial products do not release much free zinc.
• Children: evidence in children is very limited and inconsistent.

How to use zinc for a cold

If you want to try zinc lozenges:

1. Start within 24 hours of the first symptoms. Starting later is unlikely to help.
2. Choose zinc acetate or zinc gluconate lozenges. Avoid products where citric acid, tartaric acid or similar ingredients appear near the top of the list.
3. Let the lozenge dissolve slowly in your mouth; don't chew or swallow it whole.
4. Typical trial doses were around 75 to 100 mg of elemental zinc a day in total, split into one lozenge every 2 to 3 hours while awake.
5. Stop after 5 to 7 days, or when symptoms clear.

These doses are above the long-term upper limit for adults (40 mg a day), which is why they should only be used briefly.

Food sources of zinc include meat, shellfish (especially oysters), dairy, eggs, pumpkin seeds, nuts, beans and whole grains. Most people eating a varied diet get enough.

Possible side effects and interactions

Short-term side effects of lozenges:

• Bad or metallic taste, which is very common
• Nausea, especially on an empty stomach
• Mouth irritation

Long-term high doses (more than 40 mg a day for weeks or months):

• Copper deficiency, which can cause anaemia and nerve damage
• Lower "good" HDL cholesterol
• Weakened immune function

Interactions:

• Antibiotics: zinc reduces absorption of tetracyclines (such as doxycycline) and quinolones (such as ciprofloxacin). Take the antibiotic at least 2 hours before or 4 to 6 hours after zinc.
• Penicillamine (for Wilson's disease or rheumatoid arthritis): zinc reduces its absorption
• Thiazide diuretics increase zinc loss in urine

Who should be careful

• Children: use only doses on child-specific products and check with a pharmacist
• Pregnant or breastfeeding women: don't exceed the upper limit without medical advice
• People taking antibiotics or penicillamine (see timing above)
• People already taking multivitamins or other zinc supplements: add up your total

When to see a doctor

Most colds go away in 7 to 10 days. See a doctor if:

• Symptoms last more than 10 days or improve and then get worse again
• You have a high fever, or a fever lasting more than three days
• You have difficulty breathing, chest pain or wheezing
• You have severe sinus pain, ear pain, or a very sore throat with difficulty swallowing
• You have a long-term condition such as asthma, COPD, heart disease or a weakened immune system and symptoms are worsening
• You notice a loss of smell that does not return after the cold

Frequently asked questions

Can zinc prevent colds?

There is no good evidence that zinc supplements prevent colds in people who already get enough zinc.

Is zinc in multivitamins enough?

For general health, yes. The doses used for treating colds are much higher and short-term.

Can I take zinc and vitamin C together?

Yes. There is no harmful interaction. Vitamin C taken regularly may slightly shorten colds, but starting it after a cold begins has shown little benefit.

Why does zinc make me nauseous?

Zinc irritates the stomach lining, especially on an empty stomach. Lozenges dissolving slowly in the mouth may be easier to tolerate than tablets, and eating something beforehand helps.

References

• NIH Office of Dietary Supplements. Zinc: fact sheet for health professionals. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
• Nault D, et al. Zinc for prevention and treatment of the common cold. Cochrane Database of Systematic Reviews, 2024.
• 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.
• US Food and Drug Administration. Warnings on three Zicam intranasal zinc products, 2009.