Zinc Supplements: Who Needs Them, What Trials Show, and the Copper Risk

Zinc is a mineral your body uses for immune cells, wound repair, taste and hundreds of enzymes. Adult men need 11 mg a day and women 8 mg, mostly from meat, seafood, dairy, beans and whole grains. Supplement labels list elemental zinc, the zinc itself, not the weight of the whole compound (NIH ODS). This guide covers adults.

The short version

• Colds, in adults and children who already have one (zinc against placebo): about 2 days shorter in 8 treatment trials (Nault 2024); in 7 lozenge trials giving 80 mg a day or more, colds were about a third (33%) shorter (Hemilä 2017). B Grade B.
• Daily zinc to avoid colds (adults and children, against placebo): little or no difference. B Grade B (Nault 2024).
• Macular degeneration, adults with intermediate disease (against placebo): a high-dose zinc and antioxidant formula slowed the slide to late disease. B Grade B (Evans 2023).
• Acne (against placebo, or an antibiotic): fewer inflamed spots in small trials, about half the effect of minocycline. B Grade B (Verma 1980; Dreno 2001).
• Too much for too long: copper deficiency, with anemia and spinal cord damage, in case series and drug-safety reports. C Grade C for harm (Dutta 2026; Chen 2024).

Who is likely to be low in zinc?

Most people in the US get enough zinc from food. Those more likely to run short include people with Crohn's, ulcerative colitis or coeliac disease, weight-loss surgery that bypasses part of the gut, a vegetarian or vegan diet, alcohol use disorder or sickle cell disease (studied mainly in children), older adults who eat little, and anyone pregnant or breastfeeding (NIH ODS). Across 26 studies, vegetarians had slightly lower zinc intakes and blood zinc than meat eaters, and vegans more so (Foster 2013). In 12 studies (2,529 people), blood zinc fell during the first year after gastric bypass but not clearly after sleeve gastrectomy (Zhu 2026). If you are pregnant or breastfeeding, take the amount your midwife or obstetric team advises.

Low zinc can dull taste and smell and, in older adults, slow wound healing and change thinking and mood (NIH ODS). Blood tests are imperfect: readings shift with age, sex, time of day and illness. Among 70 hospital patients prescribed zinc, 48% had low readings probably caused by illness or low blood protein, not true deficiency (Duncan 2015).

Do zinc lozenges help a cold?

B Grade B: yes, if you start early (people with a cold, against placebo). Pooling 8 treatment trials of zinc in various forms (972 people; the review's 34 trials included 12 in children), colds ended 2.37 days sooner on zinc, at low certainty because the trials varied so much (Nault 2024). In 7 lozenge trials (575 people with natural colds), colds were 33% shorter; acetate (40%) and well-made gluconate (28%) lozenges did not differ clearly (Hemilä 2017). The form and dose matter: the researchers behind the acetate trials advise lozenges that release zinc ions, started within 24 hours of the first symptoms and used for less than 2 weeks, and an earlier analysis found low-dose lozenges had no effect (Hemilä 2015). More in cold and flu season supplements and the common cold.

The lozenge trials gave 80 to 92 mg of zinc a day, and two gave about 200 mg, with no extra benefit above 100 mg (Hemilä 2017). That is above the adult upper limit of 40 mg a day, because weeks of high doses can drain copper; ask a pharmacist or clinician before using lozenge doses, keep them to the days of a cold, and don't go above 40 mg for longer without blood tests (NIH ODS; check your stack).

B Grade B: daily zinc did not clearly cut colds (against placebo). The risk of catching one barely changed (risk ratio 0.93, 9 trials, 1,449 people, low certainty); minor side effects, the review's examples being an unpleasant taste or stomach cramps, were more common with zinc for colds (risk ratio 1.34, 16 trials, 2,084 people) (Nault 2024), and nausea was one of the minor side effects named in another review (Hunter 2021). The zinc page shows D for the risk of upper respiratory infections, from one trial; these 9 pooled trials support B for little or no effect.

Does zinc help your immune system?

C Grade C: one small trial in older adults (against placebo). In 50 healthy adults aged 55 to 87, 45 mg of zinc a day as zinc gluconate for a year meant fewer infections and higher blood zinc than placebo (Prasad 2007). That trial dose tops the 40 mg adult limit, and months above it can lower copper, so take that much only with a clinician's advice and blood tests (NIH ODS). A 2021 review that found fewer respiratory infections in adults had pooled zinc by mouth with nasal zinc (Hunter 2021). The zinc page shows no effect on respiratory infection risk, from one trial; the trial here counted all infections in older adults.

C Grade C: no clear help for COVID-19 (against usual care). In 214 adults with COVID-19 at home, 10 days of high-dose zinc gluconate, with or without vitamin C, did not shorten symptoms; the trial stopped early (Thomas 2021).

Does zinc help acne?

B Grade B: a modest help for inflamed spots, less than an antibiotic. We keep B, as our zinc and acne pages do, because several controlled trials found some benefit, though they are small and old. In small placebo-controlled trials from 1978 to 1989, 17 of 29 people with acne (58%) improved on zinc sulphate over 12 weeks, against none on placebo (Verma 1980), and 30 mg of zinc a day as zinc gluconate lowered inflammation scores (Dreno 1989). In a third trial of 52 people, zinc helped only pustules, and half of those on it had nausea, vomiting or diarrhea (Weimar 1978). In 332 people with inflamed acne, 30 mg of zinc a day for 3 months cut inflamed spots by more than two thirds in 31%, against 63% on the antibiotic minocycline (Dreno 2001). A 2023 review of oral acne supplements flagged stomach side effects with zinc (Shields 2023). One older trial gave 600 mg of zinc sulphate a day (Verma 1980), which supplies far more zinc than the 40 mg limit; long courses like that can cause copper deficiency, so only under a clinician. See the acne protocol.

Does zinc slow macular degeneration?

B Grade B: yes, for adults with intermediate age-related macular degeneration (AMD), against placebo. AMD damages the centre of the retina and blurs central vision. In AREDS, 3,640 adults aged 55 to 80 took 80 mg of zinc (as zinc oxide) with 2 mg of copper, antioxidants (vitamins C and E and beta-carotene), both, or placebo for an average of 6.3 years; advanced AMD was less likely on the combination (odds ratio 0.72), and zinc alone came close (0.75) (AREDS 2001). A 2023 Cochrane review rated this moderate certainty, mostly from AREDS: about 78 fewer people per 1,000 with intermediate AMD reached late AMD on the formula, and only about 4 fewer per 1,000 with early AMD (Evans 2023). In AREDS2, lowering the zinc dose made no apparent difference to progression (AREDS2 2013); NIH ODS gives that dose as 25 mg, calls the finding preliminary, and says the National Eye Institute still advises 80 mg (NIH ODS).

The 80 mg is a trial dose for diagnosed AMD, on an eye doctor's advice. Upper limit for adults: 40 mg of zinc a day, since taking more for months can bring on copper deficiency; take more only with blood tests or your clinician's advice (NIH ODS; check your stack). People on the zinc versions were admitted to hospital for urinary problems more often (11.1% against 7.6%), most clearly men (grade C for harm, Johnson 2007). Beta-carotene versions brought more lung cancers (2.0% against 0.9%), mostly in former smokers (AREDS2 2013). See the macular degeneration protocol.

Does zinc help wounds and ulcers heal?

C Grade C: no clear benefit for leg ulcers (oral zinc sulphate against placebo). In 4 small trials in people with venous leg ulcers, healing did not clearly differ (risk ratio 1.22); the review's 6 trials (183 people) were small and poorly reported (Wilkinson 2014). For pressure sores, a 2024 Cochrane review called the evidence on a drink combining protein, arginine, zinc and antioxidants very uncertain for avoiding new sores (Langer 2024). In 200 malnourished adults with pressure sores, such a drink shrank them more than a matched drink did (60.9% against 45.2% in 8 weeks), but zinc's own part can't be separated (Cereda 2015). See wound healing and the wounds and burns protocol.

Does zinc lower blood sugar?

B Grade B: small drops in blood sugar markers, mostly in people with diabetes, against placebo. Don't stop, skip or swap a diabetes medicine for zinc. A 2019 review of 32 placebo-controlled comparisons (1,700 people) found lower fasting and after-meal blood sugar and HbA1c (a 3-month average) on zinc, most clearly in people with diabetes (Wang 2019). Wang 2019 pooled several trials from a research group whose trials have been retracted or questioned (one has since been retracted). Two earlier reviews without those trials found the same small fall in fasting blood sugar (Capdor 2013; Jayawardena 2012). A 2026 review found less insulin resistance but no clear change in blood sugar or HbA1c; 5 of its 18 trials came from that group, and LDL cholesterol rose slightly (Loaiza-Giraldo 2026). New cases of diabetes went uncounted: a Cochrane review found 3 small trials in adults with insulin resistance, none reporting them (El Dib 2015). See supplements for blood sugar.

Does zinc help mood, taste, hair or testosterone?

• Depression, added to antidepressants: grade C. In 5 placebo-controlled trials, scores fell a little, but not when trials were split by size (da Silva 2021). See supplements and antidepressants.
• Taste problems: grade C. In people whose taste loss was unexplained or due to low zinc, zinc beat placebo on taste tests in 3 trials (366 people), on very low-quality evidence (Kumbargere Nagraj 2017).
• Hair loss: grade D. Of 15 people with patchy hair loss (alopecia areata) and low zinc, 9 improved, with no comparison group and no statistically clear result (Park 2009). See supplements for hair loss.
• Testosterone: grade D, and only if you are low. It rose in 9 older men with marginal zinc deficiency, with no placebo group (Prasad 1996); in 14 exercising young men who ate enough zinc, a high-dose zinc and magnesium product left it unchanged (grade C, Koehler 2009). Our zinc page shows C for a small rise in free testosterone in athletes, from small trials; in this trial of men who already ate enough zinc, it did not change. See supplements for low testosterone.

What is the best form of zinc?

C Grade C, absorption only: head-to-head studies measured zinc in the blood, not health. In 15 healthy adults, zinc citrate and zinc gluconate were absorbed equally (about 61%) and zinc oxide less (50%); three people absorbed little or none from oxide (Wegmüller 2014). After one dose in 12 women, zinc bisglycinate gave 43% more zinc in the blood than gluconate (Gandia 2007), and over 4 weeks in 15 people, picolinate raised hair, urine and red-cell zinc while citrate and gluconate did not (Barrie 1987). For colds, the tested forms are acetate and gluconate lozenges; AREDS used zinc oxide tablets.

When should you take zinc, and what shouldn't you take it with?

No trial has compared times of day for a health outcome. C Grade C (absorption studies): iron of 25 mg or more taken at the same time can lower zinc absorption (NIH ODS), and in 11 young women with low iron stores, 22 mg of zinc a day for 6 weeks lowered ferritin, the iron-store marker (Donangelo 2002). In adults aged 21 to 69, a 600 mg calcium supplement taken with a meal halved zinc absorption from that meal (Wood 1997). Take zinc, iron and calcium at different times; see iron supplements. Beans and whole grains contain phytates, which bind zinc (NIH ODS).

What we'd skip

• Nasal zinc gels, sprays and swabs: lost sense of smell, sometimes for good (FDA 2009).
• Daily zinc all winter to avoid colds: little or no effect (Nault 2024).
• Zinc for male fertility: in 2,370 men in couples having fertility treatment, folic acid plus zinc did not raise live births (34% against 35% on placebo), slightly raised sperm DNA damage and upset more stomachs, and sperm count and movement did not improve; the trial combined zinc with folic acid, and the zinc page's grade C rows rest on smaller trials (Schisterman 2020); see supplements for low sperm count.
• More than 40 mg a day for months without a clinician: in one hospital audit, most patients prescribed zinc got doses high enough to lower copper, and only 2 of 70 had copper checked (Duncan 2015).

Safety and interactions

• Upper limit for adults: 40 mg of zinc a day from food and supplements. Above it, zinc can cause copper deficiency, and 50 mg or more a day for weeks can also weaken immunity and lower HDL ("good") cholesterol; go higher only with blood tests or your clinician's advice (NIH ODS). Lozenges, multivitamins and immune or hair blends add up: check your stack; see do you need a multivitamin?
• Copper deficiency: in 37 published cases, extra zinc (about 50 mg a day or more, for weeks to years, mostly from supplements or denture creams) caused anemia in nearly all, often with low white blood cells; blood counts usually recovered on stopping zinc and taking copper, but nerve damage healed more slowly (Dutta 2026). Of 198 people with spinal cord damage from low copper (copper deficiency myelopathy), 39 had used zinc denture cream; only 24% improved with copper and 5% fully recovered (Chen 2024). See copper deficiency.
• Denture creams: some contain 17 to 34 mg of zinc per gram; harm has followed heavy use (70 g or more a week for years), and many creams are now zinc-free (NIH ODS).
• Never use zinc in your nose. In 2009, the FDA told people to stop using three nasal zinc cold products after more than 130 reports of lost smell, which may be long-lasting or permanent (FDA 2009). One clinic saw 17 people who felt burning after sniffing a zinc gel, then lost smell within 48 hours (Alexander 2006). Lozenges and tablets are a different route.
• Stomach and other effects: zinc often causes nausea; in trials for respiratory infections, about 1 extra person in 7 had a minor side effect such as nausea or mouth irritation (Hunter 2021). High intakes can cause nausea, vomiting, loss of appetite, stomach upset, dizziness and headaches (NIH ODS).
• Children: keep zinc tablets and lozenges out of their reach; if a child swallows several, call Poison Control (1-800-222-1222 in the US) or emergency services (Poison Control).
• Medicines. Don't stop, skip or swap a prescribed medicine; ask your prescriber or pharmacist about spacing.
  • Quinolone antibiotics such as ciprofloxacin: the label says to take the antibiotic at least 2 hours before or 6 hours after products containing zinc (DailyMed). In 12 healthy men, a multivitamin with zinc lowered ciprofloxacin levels (Polk 1989).
  • Tetracycline antibiotics: zinc preparations impair their absorption (DailyMed).
  • Penicillamine (for Wilson disease and rheumatoid arthritis): take it at least 1 hour apart from zinc (DailyMed).
  • Thiazide diuretics (water pills such as hydrochlorothiazide or chlorthalidone) raise zinc loss in urine (NIH ODS).
• Kidney disease or age 70 and over: among 2,646 Japanese drug-safety reports on adults taking zinc by mouth, 100 (3.8%) reported copper deficiency; it was reported more often with chronic kidney disease, higher doses or age 70 and over (Hiyama 2026). With kidney disease, ask your kidney team first.

When to see a doctor

• Soon, if you take zinc regularly or use a lot of denture cream: numbness or tingling in your feet or hands, an unsteady walk, falls or weak legs (possible spinal cord damage from copper deficiency), or tiredness, breathlessness and pale skin (possible anemia). Ask for copper and blood count tests.
• A cold that lasts more than 10 days, a high fever, or trouble breathing: see a doctor; see cold and flu season supplements.
• Loss of smell after a nasal product, or urinary pain, blood in the urine or trouble passing urine on high-dose zinc.
• Before starting: kidney disease, Wilson disease, penicillamine, a quinolone or tetracycline antibiotic, a thiazide diuretic, or a plan to take more than 40 mg a day.
• Signs of low zinc (taste or smell changes, slow healing) with a risk factor above: get tested rather than guessing.

Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. If you are pregnant or breastfeeding, ask your midwife or obstetric team. If you are under 18, ask a clinician.

FAQ

Should I take zinc every day? Only if you are likely to be low or a clinician advises it. Against placebo, daily zinc did not clearly cut colds (grade B). The adult upper limit is 40 mg a day; more for months can cause copper deficiency.

What is the best form of zinc? For a cold, the tested forms are zinc acetate or gluconate lozenges, begun within 24 hours. In 15 healthy adults, citrate and gluconate were absorbed equally and oxide less (grade C, absorption only).

Can I take zinc and iron together? Take them at different times. Iron of 25 mg or more taken with zinc can lower zinc absorption, and in 11 young women with low iron stores, daily zinc lowered those stores further (grade C).

Can too much zinc cause copper deficiency? Yes. Published cases link about 50 mg a day or more, over weeks to years, to anemia, low white cells and spinal cord damage (grade C, case series). Stay within 40 mg a day unless a clinician checks your copper.

Related pages

• Zinc · Copper · Copper deficiency · Common cold · Wound healing
• Acne protocol · Macular degeneration protocol · Wounds and burns protocol
• Cold and flu season · Hair loss · Low testosterone · Warts · Eczema · Iron · Multivitamins
• Check my stack · How we grade

Sources

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