What Not to Take With Zinc (and What's Fine)

Don't take zinc at the same time as iron supplements of 25 mg or more, tetracycline or quinolone antibiotics, or penicillamine. Also avoid 50 mg or more a day for weeks, which can interfere with copper absorption¹.

Calcium and magnesium are weaker, dose-dependent conflicts. The rest of the usual "never take together" lists are mostly a matter of spacing doses. This guide covers each pairing for zinc, with the trial numbers.

These pairings have the strongest support for avoiding or separating doses:

• Iron supplements of 25 mg or more: taken at the same time, they can lower zinc absorption and plasma zinc¹.
• Tetracycline and quinolone antibiotics: zinc and the antibiotic can bind in the gut, which can block absorption of both¹.
• Penicillamine: zinc can reduce its absorption and action, so take them at least 1 hour apart¹.
• Zinc doses of 50 mg or more a day for weeks: these can interfere with copper absorption, immune function and HDL cholesterol¹.
• Zinc nasal gels: a 17-patient case series and a 25-patient clinic review tie intranasal zinc gluconate gel to loss of smell^{2, 3}.

Calcium, magnesium and phytate-rich foods depend on the dose and the meal, as the sections below show.

Iron mostly lowers zinc absorption when both are swallowed together as supplements, and the effect largely disappears when they come with a meal. In 11 adults with an ileostomy, zinc absorption fell from 44% with no iron to 26% with 100 mg of iron and 23% with 400 mg⁴.

An older isotope study found the same dependence on timing. At an iron-to-zinc ratio of 25:1, zinc absorption from water dropped to 34%, but the same ratio given with a meal showed no inhibition⁵. Heme iron at a 3:1 ratio did not inhibit zinc⁶.

In a trial of 13 iron-replete pregnant women, 100 mg of iron a day with meals caused no detectable harm to zinc metabolism⁷.

Does zinc block iron too?

Sometimes, at the right ratio. A review found that zinc reduced iron absorption when both were given as a fasting solution, starting at a 1:1 zinc-to-iron ratio with a 10 mg iron dose. The effect was not seen in a hamburger meal, formula or milk⁸.

Trials of daily zinc give mixed answers. In 11 young women with low iron stores, 22 mg of zinc a day for 6 weeks lowered ferritin and transferrin saturation⁹. But 20 mg a day between meals for 2 months did not change iron absorption or status in 44 Chilean women¹⁰. A review of supplementation trials concluded that zinc alone has no clinically important negative effect on iron status, although iron indicators improve less when the two are given together¹¹.

If you are treating iron deficiency, take iron and zinc at different meals. Iron absorption also depends on what else is on the plate.

It can at supplement doses, but the trials disagree. In 18 postmenopausal women, adding about 468 mg of calcium a day as milk or a calcium phosphate supplement cut net zinc absorption and zinc balance by about 2 mg a day¹². In a second study in the same paper, a 600 mg calcium carbonate supplement taken with a meal halved zinc absorption, and an extra 7.8 mg of zinc offset the loss¹².

In 9 women, plasma zinc after a 4.5 mg zinc dose was much lower with 600 mg of calcium as carbonate or citrate than with zinc alone¹³.

Other trials found no effect:

• Whole-diet study in 10 women: diets with about 700 or 1,800 mg of calcium a day gave the same zinc absorption¹⁴.
• Balance study in adult men: calcium intakes from 200 to 2,000 mg a day did not change zinc balance¹⁵.

The practical reading is that the evidence is mixed for both milk-type food calcium and supplements: one balance study found an effect from each, and two others found none. The cautious option is to take a calcium supplement at a different meal from zinc. Our guide to taking zinc, magnesium and calcium together covers the schedule, and the calcium page covers the mineral itself.

Yes, at high doses taken for weeks or longer. The upper limit for adults is 40 mg of zinc a day, and 50 mg or more over weeks can interfere with copper absorption¹.

• Case report: a 57-year-old man who took large amounts of over-the-counter zinc for more than 18 months developed microcytic anemia, which corrected after he stopped¹⁶.
• Prescribing review: of 70 patients prescribed zinc, 62% received doses high enough to cause copper deficiency. Plasma copper was measured in only 2, and 9% developed unexplained anemia and 7% neurological symptoms typical of copper deficiency¹⁷.
• Denture cream: products with 17 to 34 mg of zinc per gram have caused copper deficiency and nerve damage when used heavily for years, and four patients were described in one case series^{1, 18}.

Some high-dose zinc products add copper. The eye-disease trial formula paired 80 mg of zinc with 2 mg of copper, and adults aged 50 to 80 at high risk of advanced macular degeneration had a 25% lower risk after 5 years¹. Ask a clinician before adding copper yourself. If you take 50 mg or more of zinc under medical care, ask about checking copper. See the copper page and copper deficiency for symptoms.

At high doses, yes. In 3 groups of adult men, 142 mg of zinc a day lowered magnesium absorption and balance¹⁹.

A lower dose also had an effect. In 25 postmenopausal women, 53 mg of zinc a day for 90 days increased magnesium losses in feces and urine and lowered magnesium balance²⁰.

Both trials used doses above the 40 mg upper limit¹, so they do not show that lower supplement doses cause a problem. If your diet is already low in magnesium, a high-dose zinc supplement is the situation to avoid. See what not to take with magnesium for the other side.

Antibiotics

Tetracycline and quinolone antibiotics can bind zinc in the gut. Taking the antibiotic at least 2 hours before or 4 to 6 hours after the zinc supplement minimizes this¹. In a crossover study of 7 volunteers, 45 mg of zinc taken with 500 mg of tetracycline cut tetracycline levels by about 30%, while doxycycline absorption did not change significantly²¹.

A review of quinolone interactions found that chelation with minerals occurred in 22% to 76% of patients prescribed fluoroquinolones, with zinc having a smaller effect than antacids and iron²². See antibiotics and supplements for what else to space.

Penicillamine

Zinc can reduce the absorption and action of penicillamine, a drug for rheumatoid arthritis and Wilson disease. Keep them at least 1 hour apart¹.

Thiazide diuretics

These are not a conflict to space but a reason zinc can run low. Thiazides such as chlorthalidone and hydrochlorothiazide increase zinc excretion in urine¹. In a randomized trial, total urinary zinc rose by 60% during thiazide treatment²³. A systematic review of 8 small studies found that ACE inhibitors, angiotensin receptor blockers and thiazides may lower zinc levels²⁴. Ask your prescriber before adding zinc, and don't treat a low result with a high dose on your own.

Diet and alcohol also affect zinc. Phytate, the storage form of phosphorus in beans, nuts and whole grains, binds zinc in the gut. In a stable-isotope study of young men, zinc absorption fell from 34.0% on a basal diet to 17.5% when phytate was added to reach a phytate-to-zinc molar ratio of 15²⁵. A systematic review found that ratios above 15 lowered fractional zinc absorption by 0.14, to 45% of the control value²⁶.

Soaking beans, grains and seeds before cooking can reduce this binding¹. Alcohol lowers zinc absorption and raises urinary zinc loss, and low zinc status is seen in 30% to 50% of people with alcohol use disorder¹. Inflammatory bowel disease and bariatric surgery also raise the risk of low zinc¹.

What are the warning signs of zinc deficiency?

The signs vary by age. In children they include diarrhea, slowed growth and hair loss. In older adults they can include slow wound healing and changes in thinking, and deficiency at any age can disturb taste and smell¹. These signs overlap with many other conditions, so see our zinc deficiency page and ask about testing. Blood zinc is an imperfect test: levels vary with sex, age and time of day, and below 70 mcg/dL in women or 74 mcg/dL in men suggests inadequate status¹.

The daily recommendation for adults is 11 mg for men and 8 mg for women, and the upper limit is 40 mg¹.

Children's limits are much lower: 7 mg at ages 1 to 3, 12 mg at 4 to 8, 23 mg at 9 to 13 and 34 mg at 14 to 18, including in pregnancy¹. Check any dose for a child with a pediatrician, and with a clinician if you are pregnant. The limits do not apply to zinc given as medical treatment under a physician's care¹. For adults, a 30 mg supplement is below the limit. A 50 mg tablet is above it, which is why taking one every day for weeks is the pattern linked to copper problems¹.

The NIH fact sheet mentions a Cochrane review of HIV trials that included one weekly 90 mg dose for 6 months, but it reports no copper outcome for that regimen¹. We found no trial of weekly dosing that tested copper, so we can't say. The 40 mg upper limit and the 50 mg threshold for copper effects are daily figures¹.

Can zinc raise PSA levels?

We did not find a trial that measured PSA after zinc supplements. In 47,240 men followed for about 28 years, supplemental zinc was not linked to overall prostate cancer, but more than 75 mg a day went with a higher risk of lethal disease (hazard ratio 1.76)²⁷. In 5,089 US men, cadmium exposure went with higher PSA only at high dietary zinc intake (14.12 mg a day or more)²⁸. These are associations, so tell your clinician about any supplement before a PSA test.

Which fruit is rich in zinc?

None. Fruits and vegetables contain very little zinc, and half a cup of blueberries has about 0.1 mg. The richest foods are oysters (32 mg in 3 ounces of farmed Eastern oysters), beef (3.8 mg in 3 ounces of sirloin) and pumpkin seeds (2.2 mg in an ounce)¹. See our guide to foods high in zinc.

Few supplements need to be taken with zinc. The evidence covers combinations used in trials, not proven benefits of pairing.

• Copper: relevant when zinc is high or long-term. The eye-disease formula that slowed macular degeneration combined 80 mg of zinc with 2 mg of copper¹.
• Vitamin C: in the same eye-disease formula, with 500 mg of vitamin C alongside the zinc¹. We found no study showing that vitamin C blocks zinc absorption.
• A meal: food removed the iron effect on zinc absorption in the older isotope study⁵.

Lozenge or syrup zinc taken shortly after a cold starts is the use with the most support¹. A meta-analysis of 7 lozenge trials in 575 people, mostly using 80 to 92 mg of zinc a day, found colds were 33% shorter, with no evidence that doses above 100 mg a day work better²⁹.

The overall picture is less clear than that headline. A 2012 meta-analysis of 17 trials (2,121 people) found colds shorter by 1.65 days, with very high heterogeneity, and more bad taste (RR 1.65) and nausea (RR 1.64) with zinc³⁰. The 2024 Cochrane review of 34 studies (8,526 people) found zinc may do little or nothing to prevent colds (RR 0.93), and it may shorten an existing cold by about 2.4 days with low-certainty evidence³¹. The NIH fact sheet says lozenges or syrup shorten a cold but do not reduce its severity¹.

These lozenge doses are about twice the 40 mg upper limit and were used for days while a cold lasted, not for weeks. The evidence does not set a recommended dose, and the Cochrane review found probably more non-serious side effects with zinc treatment (RR 1.34)³¹. Longer use at that level risks copper depletion.

For the full picture see zinc for cold prevention. For COVID-19, results conflict: a trial of 470 patients found fewer ICU admissions with zinc³², while a trial of 214 outpatients found no benefit from 10 days of 50 mg zinc gluconate, 8,000 mg of ascorbic acid or both³³.

No trial we found compared morning with night, so choose the time that keeps zinc away from the things above. Separating doses is what the evidence supports. A sample day, as one reasonable arrangement and not a tested protocol:

• Breakfast: iron, if you take it.
• Lunch: calcium, if you take it.
• Dinner: zinc, with food.
• Antibiotic days: the antibiotic at least 2 hours before or 4 to 6 hours after zinc¹.

For a wider schedule that includes other vitamins, see when to take vitamins. For the immune angle, see the immune system hub.

Supplements in this guide

• Zinc
• Iron
• Copper
• Calcium
• Magnesium
• Vitamin C

We searched PubMed for human studies of zinc with iron, calcium, copper, magnesium, antibiotics and diuretics, and for zinc in colds, COVID-19 and prostate health. We read the NIH Office of Dietary Supplements zinc fact sheet and 32 journal records, and cited all of them. We prioritized randomized trials, controlled metabolic studies and systematic reviews, and used case reports only for rare harms.

The evidence is thin on practical questions: most interaction studies used single doses or small groups, and none compared morning with night. This guide was assembled on 2 November 2026 and is not medical advice.

1. National Institutes of Health, Office of Dietary Supplements. Zinc: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
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3. Davidson TM, et al. The Bradford Hill criteria and zinc-induced anosmia: a causality analysis. Arch Otolaryngol Head Neck Surg. 2010;136(7):673-6. doi:10.1001/archoto.2010.111
4. Troost FJ, et al. Iron supplements inhibit zinc but not copper absorption in vivo in ileostomy subjects. Am J Clin Nutr. 2003;78(5):1018-23. doi:10.1093/ajcn/78.5.1018
5. Sandström B, et al. Oral iron, dietary ligands and zinc absorption. J Nutr. 1985;115(3):411-4. doi:10.1093/jn/115.3.411
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18. Nations SP, et al. Denture cream: an unusual source of excess zinc, leading to hypocupremia and neurologic disease. Neurology. 2008;71(9):639-43. doi:10.1212/01.wnl.0000312375.79881.94
19. Spencer H, et al. Inhibitory effects of zinc on magnesium balance and magnesium absorption in man. J Am Coll Nutr. 1994;13(5):479-84. doi:10.1080/07315724.1994.10718438
20. Nielsen FH, et al. A moderately high intake compared to a low intake of zinc depresses magnesium balance and alters indices of bone turnover in postmenopausal women. Eur J Clin Nutr. 2004;58(5):703-10. doi:10.1038/sj.ejcn.1601867
21. Penttilä O, et al. Effect of zinc sulphate on the absorption of tetracycline and doxycycline in man. Eur J Clin Pharmacol. 1975;9(2-3):131-4. doi:10.1007/BF00614009
22. Lomaestro BM, et al. Absorption interactions with fluoroquinolones. 1995 update. Drug Saf. 1995;12(5):314-33. doi:10.2165/00002018-199512050-00004
23. Wester PO. Urinary zinc excretion during treatment with different diuretics. Acta Med Scand. 1980;208(3):209-12. doi:10.1111/j.0954-6820.1980.tb01179.x
24. Braun LA, et al. Pharmaco-nutrient interactions - a systematic review of zinc and antihypertensive therapy. Int J Clin Pract. 2013;67(8):717-25. doi:10.1111/ijcp.12040
25. Turnlund JR, et al. A stable isotope study of zinc absorption in young men: effects of phytate and alpha-cellulose. Am J Clin Nutr. 1984;40(5):1071-7. doi:10.1093/ajcn/40.5.1071
26. Bel-Serrat S, et al. Factors that affect zinc bioavailability and losses in adult and elderly populations. Nutr Rev. 2014;72(5):334-52. doi:10.1111/nure.12105
27. Zhang Y, et al. Zinc supplement use and risk of aggressive prostate cancer: a 30-year follow-up study. Eur J Epidemiol. 2022;37(12):1251-1260. doi:10.1007/s10654-022-00922-0
28. Fang Y, et al. Exposure to heavy metal elements may significantly increase serum prostate-specific antigen levels with overdosed dietary zinc. Ecotoxicol Environ Saf. 2024;272:116080. doi:10.1016/j.ecoenv.2024.116080
29. 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;8(5):2054270417694291. doi:10.1177/2054270417694291 Our study summary.
30. Science M, et al. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012;184(10):E551-61. doi:10.1503/cmaj.111990 Our study summary.
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32. Ben Abdallah S, et al. Twice-Daily Oral Zinc in the Treatment of Patients With Coronavirus Disease 2019: A Randomized Double-Blind Controlled Trial. Clin Infect Dis. 2023;76(2):185-191. doi:10.1093/cid/ciac807
33. Thomas S, et al. Effect of High-Dose Zinc and Ascorbic Acid Supplementation vs Usual Care on Symptom Length and Reduction Among Ambulatory Patients With SARS-CoV-2 Infection: The COVID A to Z Randomized Clinical Trial. JAMA Netw Open. 2021;4(2):e210369. doi:10.1001/jamanetworkopen.2021.0369 Our study summary.