When to take

Short answer

No time of day has been shown to be superior for everyone for taking zinc. The more concrete points are these: a supplement taken between meals raises blood zinc more than zinc taken with food, but high intake can upset the stomach; 25 mg or more of elemental iron and some antibiotics can interact with zinc; intranasal zinc products have been associated with loss of smell. The product instructions and the physician’s plan take priority. ^{[1] [2]}

Is zinc taken fasting or with food?

Two results should be read together. First, the BOND zinc panel reports that plasma zinc responds more to a supplement taken between meals than to additional zinc from food; that is, the reflection in blood level is more marked when taken apart from a meal. Second, phytate in plant foods reduces zinc absorption, and absorption from mixed meals is lower than from meals containing only animal foods. ^{[2] [1]}

On the other hand, when zinc is taken in high amounts it can cause nausea, dizziness, headache, stomach upset, vomiting and loss of appetite. ^[1] Whether taking the supplement with food reduces nausea has not been reported as a measured result; absorption can decrease with mixed meals. In a person with stomach complaints, timing is evaluated together with the product instructions and a pharmacist or physician.

In short: there is no general rule of “best fasting” or “best with food”; there is a balance between absorption and tolerance.

Can zinc and iron be taken at the same time?

NIH reports that taking supplements containing 25 mg or more of elemental iron at the same time as a zinc supplement can reduce zinc absorption and plasma zinc level. In contrast, iron in fortified or enriched foods does not block zinc absorption. ^[1]

This information is a reason for people who use both iron and zinc supplements to look at product labels; it is not a usage schedule. While iron deficiency treatment is ongoing, the timing of the two supplements is planned together with a physician. The content of multivitamin and mineral products also needs to be included in the total.

NIH’s zinc fact sheet does not specify a one-hour interval between zinc and calcium or magnesium supplements. Taking calcium and iron supplements at different times of day appears in NIH’s iron fact sheet; that very high amounts of zinc can impair magnesium absorption is covered in the magnesium guide.

Detailed guideWhen to take iron medication? Tea, calcium and drug intervals→

How should intervals with antibiotics and other drugs be?

NIH’s interactions section states the following. ^[1]

The ciprofloxacin drug information (MedlinePlus) gives a longer interval for this antibiotic: it states that antacids and multivitamins containing zinc, iron, calcium or magnesium are taken at least 6 hours before or 2 hours after ciprofloxacin. ^[6] These intervals do not replace the drug’s package insert or the physician’s instructions. When zinc supplements are considered in people who use medications regularly, a pharmacist’s or physician’s opinion makes it easier to notice interactions.

Zinc forms: gluconate, sulfate, acetate, citrate, picolinate

NIH says that forms such as zinc sulfate, zinc acetate and zinc gluconate are found in supplements. In the “Supplement Facts” section of the label, the amount of elemental zinc is written, not the weight of the whole compound. ^[1]

For this reason, “50 mg of zinc gluconate” and “50 mg of elemental zinc” are not the same thing. The elemental zinc amount on the label is the number to be compared with the upper limit together with that from food.

In terms of absorption, in young adults absorption from zinc citrate and zinc gluconate supplements is similar (about 61%), and from zinc oxide it is 50%. ^[1] Other forms such as picolinate are seen on labels; the sources of this guide do not compare these forms, and no conclusion can be drawn about the superiority of one form over another. Before the product form, the purpose (completing daily intake, treating a diagnosed deficiency or a specific condition) needs to be determined.

In what time window were zinc lozenges studied in colds?

NIH states that zinc in lozenge or syrup form appears to shorten duration when taken shortly after symptoms begin. In one of the studies it reports, 50 adults, starting within 24 hours of symptom onset, took a zinc acetate lozenge (13.3 mg zinc) or placebo every 2–3 hours while awake throughout symptoms, and the cold was shortened by 3 days in the lozenge group. In another study (273 adults, experimental cold), zinc gluconate lozenges (13.3 mg zinc) given every 2–3 hours while awake, six lozenges per day in total, shortened duration by 1 day, while acetate lozenges with lower amounts (5.0 and 11.5 mg) showed no effect; in a third study, no lozenge showed an effect. ^[1]

The 2024 Cochrane review reports that gluconate was the most common form in lozenge studies, and that zinc gluconate was given at 45–276 mg per day for 4.5–21 days. In treatment studies, a mean shortening of 2.37 days (low certainty) and an increase in non-serious side effects (RR 1.34) were found. ^[3]

What is described here are study conditions; it is not a recommendation on how much, how often and for how long to use. NIH states that no general recommendation can be given for the most suitable amount, form and timing. In the 273-person study reported by NIH, six 13.3 mg lozenges per day add up to about 80 mg of elemental zinc; this is above the adult upper limits of 40 mg/day (NIH) and 25 mg/day (EU SCF). For this reason, short-term study conditions cannot be carried over to long-term use; with long-term high intake there is also a separate risk of copper deficiency.

Intranasal zinc

Alexander and Davidson reported 17 patients who experienced loss of smell after using intranasal zinc gluconate gel; the loss of smell had been noticed within about 48 hours. Because this risk stands out in place of the question of the “right time” for intranasal zinc products, this guide does not recommend intranasal use. ^[5]

At what time of day should a blood test be done?

If zinc level is to be measured, the time of blood draw matters. In an analysis of 4,347 people in the US, serum zinc was about 9.7 µg/dL lower in samples taken in the afternoon and about 15.3 µg/dL lower in samples taken in the evening than in samples taken in the morning. ^[4] For this reason, the time of blood draw is taken into account in interpreting the result; if a supplement was taken recently, telling the physician makes interpretation easier.

What is known and not known about timing?

Known: intake between meals raises blood zinc more, phytate reduces absorption, high amounts can upset the stomach, and 25 mg or more of elemental iron and some antibiotics interact with zinc. Not known: the effect of time of day on long-term health outcomes, a suitable interval with calcium, a clinically meaningful difference between forms, and the most suitable amount and duration in colds.

This guide does not recommend a personal dose or schedule. When supplements are considered, reviewing the elemental zinc amount on the label and the medications and products used at the same time with a health professional is the safest route.

Detailed guideZinc: overview, deficiency and upper limit→ Detailed guideZinc benefits: which effects are supported?→ Detailed guideZinc deficiency symptoms and risk groups→ Detailed guideWhich foods contain zinc?→