Which Type of Zinc Is Best? Picolinate, Citrate, Gluconate and Oxide

No type of zinc has been shown in a trial to do more for your health than another. The forms differ in how much zinc they carry by weight and, in one small fasting study of 15 adults, in the share absorbed, but no study has linked any form to a better outcome.¹ The NHS says you need "about: 9.5mg a day for men (aged 19 to 64 years), 7mg a day for women", and "Do not take more than 25mg of zinc supplements a day unless advised to by a doctor".² All seven forms are permitted in Great Britain, and once absorbed the body treats zinc the same whichever salt carried it.³ Part of the Wellgard zinc guide and the vitamins and minerals guide.

What are the different types of zinc?

The second word on the label names the partner zinc is bound to. Picolinate, citrate, gluconate and acetate are zinc bound to picolinic, citric, gluconic and acetic acid. Bisglycinate, also sold as glycinate or "chelated zinc", is zinc held between two molecules of the amino acid glycine. Sulphate is a mineral salt, the form many older trials used. Oxide is zinc and oxygen alone, the most concentrated form, dissolving in stomach acid rather than water. Sixteen zinc compounds are permitted in Great Britain, lactate, malate and pidolate among them.³

How do the forms compare?

The table is alphabetical; the evidence does not support a ranking. Zinc per 100 mg is calculated from formula weights and shifts with the water in the crystal; use the label's figure.

What did the absorption study actually find?

In 2014, 15 healthy adults took 10 mg of zinc as citrate, gluconate and oxide in turn, without food, in a randomised crossover with isotope tracers.¹ Median absorption was 61.3% from citrate, 60.9% from gluconate and 49.9% from oxide; citrate and gluconate did not differ, oxide was lower (P < 0.01), and three of the 15 absorbed little or no zinc from oxide. The authors confined their conclusion to oxide "given as a supplement without food", and no form was tested with a meal, as most multi-nutrient products are.¹ As a dose rises the percentage absorbed falls while the total absorbed still rises.⁶ What we don't know is whether the gap holds with food, at label doses daily, or changes anything a person would notice.

What is the evidence for zinc picolinate?

One study from 1987. Fifteen volunteers took picolinate, citrate, gluconate (50 mg of zinc a day) and placebo for four weeks each.⁵ Hair, urine and red-cell zinc rose significantly on picolinate and did not change on the others; serum zinc did not change on any. That is indirect status markers in 15 people, at twice the NHS supplement line, never repeated with the isotope method, and picolinate was not in the 2014 study. There is no official copper ratio for 50 mg of picolinate; the NHS line is 25 mg of supplemental zinc a day, whatever the form.² See what is zinc picolinate.

What about bisglycinate, glycinate and "chelated" zinc?

Bisglycinate and glycinate are the same compound, and "chelated" describes the bond to glycine, not a result. The evidence is one study: 12 healthy women took a single 15 mg dose as bisglycinate and as gluconate, a week apart; measured from serum zinc, bioavailability was 43.4% higher after bisglycinate, and both were well tolerated.⁴ One dose and one blood curve in 12 people, not a tracer study, not weeks of use. Bisglycinate is zinc; the mg figure beside it is what you get. No absorption comparison is an authorised claim for any form, so no label may make one.

What are zinc sulphate and zinc acetate used for?

Sulphate shows why salt weight misleads: in one trial 220 mg of zinc sulphate supplied 50 mg of zinc.⁷ The 2014 tracer study did not include it.¹ Acetate and gluconate are the lozenge forms. In the 2024 Cochrane review of 34 trials in 8,526 people, zinc taken once a cold had started may have shortened it by about 2.4 days (low certainty), with more side effects such as an unpleasant taste and stomach upset; zinc gluconate was given at 45 to 276 mg a day for 4.5 to 21 days.⁸ Across seven trials at more than 75 mg a day, acetate and gluconate did not differ significantly.⁹ Those doses are several times the NHS 25 mg line, in short courses under trial conditions; no daily zinc supplement is a cold remedy, and the lawful wording is that zinc contributes to the normal function of the immune system. Does zinc help with colds goes through the trials.

Does the form change side effects?

Nausea with zinc is about the dose and an empty stomach, not the salt. In a six-week trial of 47 volunteers taking 150 mg of zinc a day as sulphate, symptoms from headaches to vomiting were reported by 84% of the women and 18% of the men.⁷ The UK Expert Group on Vitamins and Minerals found them "particularly apparent when the supplements were taken with little or no food".¹⁰ People online describe the same: fine with breakfast, sick within minutes alone. None of the comparison studies measured nausea at label doses, so no form can be called easier on the stomach; the evidence supports a meal. Copper depends on total zinc, not the form: the NHS says "Taking high doses of zinc reduces the amount of copper the body can absorb. This can lead to anaemia and weakening of the bones"; the Expert Group placed the effect at supplemental doses of 50 mg a day and above^{2, 10} (see can you take too much zinc).

How do you read a zinc label?

Four checks answer "which zinc supplement is best".

1. Find the elemental figure. UK labels state the mineral, so "zinc (as zinc citrate) 10 mg" means 10 mg of zinc; "zinc gluconate 50 mg" alone is about 7 mg of zinc.
2. Read the % NRV. The reference value is 10 mg, so 150% is 15 mg and a "high strength" 25 mg tablet is 250%, the whole NHS allowance on its own.^{2, 13}
3. Add up every product that contains zinc. Two zinc-carrying products can together pass 25 mg. How much zinc a day gives the UK amounts by group.
4. Take it with a meal if zinc has ever made you feel sick, and follow the NHS on medicines: for ciprofloxacin, "Leave 2 hours in between taking supplements and your dose of ciprofloxacin tablets or liquid"; zinc may not mix well with doxycycline, so tell your pharmacist, as with penicillamine.¹¹ Iron at two or three times the zinc dose, swallowed together, substantially reduced zinc uptake.¹² In pregnancy, breastfeeding and for children, stay within the NHS amounts and ask a GP, midwife or pharmacist.² See what should you not take with zinc.

The wording a label may carry is the same for every form, for example "Zinc contributes to the normal function of the immune system" and "Zinc contributes to the maintenance of normal skin". Symptoms belong with a GP, not a choice of form: see signs of zinc deficiency; vitamin C and zinc together covers the commonest pairing.

Frequently asked questions

What is zinc carnosine?

Zinc bound to the dipeptide carnosine. A "gastric comfort" wording for it was refused on the Great Britain nutrition and health claims register, so no label may make it, and no study compares its absorption with other forms. Digestive symptoms are for a GP or pharmacist.

Is it better to take zinc glycinate at night or in the morning?

No trial compares times of day for any form (when is the best time to take zinc; does zinc help you sleep). Take it with a meal if it has upset your stomach, at a different time from an iron tablet and two hours from ciprofloxacin.^{11, 12} Liquids and sprays: the same rule, elemental zinc per serving.²

Is zinc oxide safe, and is it banned?

It is on the permitted list for food supplements in Great Britain and the EU.³ In the one fasting study it was absorbed less than citrate and gluconate, with absorbed zinc still rising with dose; it was not tested with food.^{1, 6} Creams and sunscreens are a separate use.

Sources

1. Wegmüller R, et al. Zinc absorption by young adults from supplemental zinc citrate is comparable with that from zinc gluconate and higher than from zinc oxide. Journal of Nutrition, 2014. PubMed 24259556.
2. NHS. Vitamins and minerals: others, including zinc and copper. nhs.uk.
3. Directive 2002/46/EC on food supplements, Annex II, as retained in Great Britain. legislation.gov.uk.
4. Gandia P, et al. A bioavailability study comparing two oral formulations containing zinc (Zn bis-glycinate vs. Zn gluconate) after a single administration to twelve healthy female volunteers. International Journal for Vitamin and Nutrition Research, 2007. PubMed 18271278.
5. Barrie SA, et al. Comparative absorption of zinc picolinate, zinc citrate and zinc gluconate in humans. Agents and Actions, 1987. PubMed 3630857.
6. King JC. Does zinc absorption reflect zinc status? International Journal for Vitamin and Nutrition Research, 2010. PubMed 21462113.
7. Samman S, Roberts DC. The effect of zinc supplements on plasma zinc and copper levels and the reported symptoms in healthy volunteers. Medical Journal of Australia, 1987. PubMed 3547053.
8. Nault D, et al. Zinc for prevention and treatment of the common cold. Cochrane Database of Systematic Reviews, 2024. PubMed 38719213.
9. 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. PubMed 28515951.
10. Expert Group on Vitamins and Minerals. Safe Upper Levels for Vitamins and Minerals, 2003. UK Government Web Archive.
11. NHS. Ciprofloxacin, and doxycycline, with other medicines and herbal supplements. nhs.uk; nhs.uk.
12. Solomons NW, Jacob RA. Studies on the bioavailability of zinc in humans: effects of heme and nonheme iron on the absorption of zinc. American Journal of Clinical Nutrition, 1981. PubMed 7223699.
13. Retained Regulation (EU) No 1169/2011, Annex XIII, nutrient reference values. legislation.gov.uk.

This article is general information, not medical advice. Keep supplemental zinc under 25 mg a day unless a doctor advises otherwise, tell your pharmacist about zinc if you take medicines, and see a GP about symptoms.