A few rules cover most of what matters. Take iron and calcium at different times. Keep iron away from tea and coffee. Take psyllium ½–1 hour apart from other supplements. Count your total zinc and vitamin D from all products: in studies, copper was affected at 50 mg of zinc a day or more for weeks. That is the point where copper is affected, not a safe level.
Several warnings online are myths or apply only at high doses. Magnesium did not change calcium absorption in studies. Vitamin C does not destroy vitamin B12. Vitamin D does not have to be taken with K2. Folic acid hides low B12 only at high doses.
Some Stivits multi-nutrient products contain calcium and iron, or calcium and zinc, in the same tablet. This guide explains what that means and how to combine Stivits products. If you take medicines, ask a doctor or pharmacist before adding supplements.
Only a few pairs need different timing: calcium with iron, tea or coffee with iron, and psyllium with other supplements. Zinc and copper is a question of dose, not timing.
| Pair | What happens | Does it matter at supplement doses | What to do |
|---|---|---|---|
| Calcium + iron | In a single meal, 165–600 mg of calcium cut iron absorption by 50–60%. In another study, 400 mg of calcium carbonate cut it from 15.8% to 4.7% | Yes for that one dose. Over months, no change in iron status in people with normal iron | Take them at different times |
| Tea or coffee + iron | Polyphenols in these drinks bind non-haem iron. 20–50 mg of polyphenols cut absorption by 50–70%, tea by 79–94% | Yes | Take iron apart from tea and coffee |
| Psyllium + other supplements | Slows absorption of what is taken at the same time | Regulatory advice, not the result of randomised trials | Take them ½–1 hour apart |
| Zinc + copper | High zinc blocks copper absorption | At 50 mg of zinc a day or more for weeks | Add up zinc from all products |
| Calcium + zinc | 600 mg of calcium cut absorption of 7.3 mg of food zinc by 50%. An extra 7.8 mg of zinc made up for it | Yes for that one dose. Long-term effect not shown | Taking them at different times is an option |
| Iron + zinc | 25 mg of iron or more lowers zinc absorption | Moderate. A 2005 review found no reason to avoid taking them together | Together is acceptable |
| Calcium + magnesium | 826 mg of magnesium did not change calcium absorption. The reverse direction was not tested directly | The EU Scientific Committee on Food: no competition under physiological conditions | Together is fine |
| Zinc + magnesium | 142 mg of zinc a day lowered magnesium absorption | Not shown at lower amounts | No action at usual amounts |
| Vitamin C + iron | Vitamin C increases iron absorption. The effect is strong in a single meal and weak across the whole diet | People with iron overload should ask a doctor | Together is fine for most people |
| Vitamin D + vitamin K2 | No harmful interaction. The role of K2 alongside D is unclear | Neither has to be taken with the other | Together or separately |
| Vitamin E + vitamin K | High-dose vitamin E can work against vitamin K. This was seen at 1000 IU a day for 12 weeks | Mainly relevant with anticoagulant medicines | Ask a doctor or pharmacist if you take anticoagulants |
| Folic acid + vitamin B12 | A large folic acid intake can hide low B12 in a blood test | Clearly above 5 mg, partly at 1–5 mg, rarely below 1 mg | No action at usual doses |
| Melatonin + valerian | No documented interaction was found in the sources checked | Absence of evidence is not proof of safety | Ask a doctor or pharmacist if you take any medicines |
You can, but iron absorption from that dose will be lower, so it is better to take them at different times. In a single meal, 165–600 mg of calcium reduced iron absorption by 50–60% (Hallberg, 1991). In another study, 400 mg of calcium carbonate lowered iron absorption from 15.8% to 4.7% (Minihane, 1998). The NIH Office of Dietary Supplements advises taking them at different times.
Long-term results look different. In longer studies, 1,200 mg of calcium a day for 6 months did not change iron stores or haemoglobin. Neither did 500 mg a day for 1 year in 113 girls. The EU Scientific Committee on Food also noted that the effect is not repeated in long studies with up to 2,000 mg of calcium. These studies were in people with normal iron. If you have been diagnosed with iron deficiency, ask your doctor or pharmacist what to take and when. This guide is not for treating any condition.
Take iron at a different time from tea and coffee. Polyphenols in these drinks bind non-haem iron: 20–50 mg of polyphenols cut iron absorption by 50–70%, and tea cut it by 79–94% (Hurrell, 1999). None of the Stivits products that contain iron include tea, coffee or guarana.
Yes. Zinc lowers copper only at high doses, so what matters is the amount, not the timing. According to the NIH Office of Dietary Supplements, the problem appears at 50 mg of zinc a day or more for weeks. At about 60 mg a day a copper-dependent enzyme decreased; in Fischer (1984) it was lower at 2 × 25 mg a day for 6 weeks. No source sets a rule for a 'zinc to copper ratio'.
If you take more than one product with zinc, add up the zinc from all of them, and do not combine several zinc products without asking a doctor or pharmacist. Seven Stivits products contain both zinc and copper, at up to 20 mg of zinc per daily serving.
Take psyllium ½–1 hour apart from other supplements. Psyllium forms a gel and can slow the absorption of what is taken at the same time. The ½–1 hour interval comes from the European Medicines Agency herbal monograph EMA/HMPC/199774/2012. It is regulatory advice, not the result of randomised trials. If you take medicines, ask a doctor or pharmacist about timing.
Take psyllium with plenty of water. Do not take it just before going to bed or if you have difficulty swallowing.
Myth 1: calcium and magnesium compete. In a study by Spencer (1994), 826 mg of magnesium did not change calcium absorption. The EU Scientific Committee on Food (2006) wrote that this competition 'is not the case under physiological conditions'. The reverse question, whether calcium lowers magnesium absorption, has not been tested directly.
Myth 2: vitamin C destroys vitamin B12. This idea came from early laboratory work. Later studies (Newmark, 1976; Marcus, 1980) did not confirm it and traced the result to a flaw in the measuring method, not to what happens in the body.
Myth 3: vitamin D must always be taken with K2. Not established. The NIH Office of Dietary Supplements describes the role of vitamin K alongside vitamin D as unclear. Vitamin D contributes to the normal absorption/utilisation of calcium and phosphorus. Vitamin K contributes to the maintenance of normal bones. Each claim applies to that vitamin on its own. A varied and balanced diet and a healthy lifestyle are important.
Myth 4: folic acid at usual doses hides low vitamin B12. According to the EU Scientific Committee on Food, folic acid clearly hides low B12 in blood tests above 5 mg a day, partly at 1–5 mg, and rarely below 1 mg. The highest amount of folate in any Stivits product is 800 µg. If you follow a vegan diet or suspect low B12, ask a doctor.
Myth 5: beta-carotene pushes out lutein. A study by Nierenberg (1997) did not confirm this. Beta-carotene has a separate warning for smokers. In the ATBC trial, 20 mg of beta-carotene a day increased lung cancer in male smokers. In the CARET trial, 30 mg of beta-carotene with retinol a day increased lung cancer in smokers and in people exposed to asbestos. Smokers are advised to avoid beta-carotene supplements (NIH Office of Dietary Supplements). Stivits Grippan Grapefruit MAX contains 2 mg of beta-carotene per 8 g serving.
Take iron products at a different time from calcium products and from multivitamins that contain calcium. Iron Complex contains 27 mg of iron as bisglycinate, 10 mg of zinc and 1.2 mg of copper. Pregnancy Plus contains 24 mg of iron; pregnant women should ask a doctor or midwife before taking iron. Take either one at a different time of day from Calcium + Vitamin D3 (450 mg of calcium per tablet), from Calcium+Magnesium+Zinc+D3 and from multivitamins with calcium, and with water rather than tea or coffee.
Four Stivits multi-nutrient products contain calcium and iron in the same tablet: Multivitamins and Minerals (260 mg calcium, 5 mg iron), Women's Vits Premium (250 mg and 7.5 mg), Hair Formula With Biotin (270 mg and 10 mg) and Skin, Hair & Nails Formula (278 mg and 1 mg). In single-meal studies, calcium at this level lowered iron absorption; these tablets themselves were not tested. In long-term studies, iron status in people with normal iron did not change.
Several Stivits products also contain calcium and zinc together, for example Men's Premium Complex (400 mg calcium, 7.5 mg zinc) and the multivitamins above. In a single-meal study, 600 mg of calcium lowered zinc absorption; a long-term effect was not shown.
Take Psyllium Husk 300g, Psyllium Husk 500g, GASTROPSYL and other products with psyllium, such as Detox Formula, ½–1 hour apart from other Stivits supplements.
Taking Vitamin C 1000 mg with Iron Complex is fine for most people: vitamin C increases iron absorption. A varied and balanced diet and a healthy lifestyle are important. Calcium+Magnesium+Zinc+D3 puts calcium and magnesium in one tablet, which is not a problem.
Zinc 25 mg contains 25 mg of zinc per tablet. Add up the zinc from all your products and do not combine several zinc products without asking a doctor or pharmacist. Vitamin D3 2000 IU, Vitamin K2 100 mcg and Vitamin K2 100 mcg + D3 4000 IU can be taken separately or together; count vitamin D from all your products.
Ask a doctor or pharmacist before adding supplements if you take medicines. If you take anticoagulants (blood thinners such as warfarin), ask your doctor before taking any vitamin K, including K2, and before taking vitamin E. Ask before combining melatonin or valerian with sedative medicines. If you have been diagnosed with iron deficiency or iron overload, or you are pregnant, ask your doctor what to take and when.
Only a few pairs need different timing: iron with calcium, iron with tea or coffee, and psyllium with other supplements (½–1 hour apart). Zinc and copper is about dose: in studies, copper was affected at 50 mg of zinc a day or more for weeks. The Stivits guide lists which Stivits products contain calcium and iron together.
Yes, calcium and magnesium can be taken together. In a study, 826 mg of magnesium did not change calcium absorption, and the EU Scientific Committee on Food (2006) wrote that competition between them 'is not the case under physiological conditions'. Stivits Calcium+Magnesium+Zinc+D3 combines both in one tablet.
Calcium lowers how much iron you absorb from the same dose: 165–600 mg of calcium cut iron absorption by 50–60% in a single meal. Long-term studies showed no change in iron status in people with normal iron. The NIH Office of Dietary Supplements advises taking them at different times, and that is how to combine Stivits Iron Complex with Stivits calcium products.
Yes, take iron at a different time from tea and coffee: tea cut iron absorption by 79–94% when drunk together. Stivits products that contain iron include no tea, coffee or guarana.
Vitamin C can be taken with iron: vitamin C increases iron absorption. The effect is strong in a single meal and weak across the whole diet. People with iron overload should ask a doctor. A varied and balanced diet and a healthy lifestyle are important. Stivits Iron Complex can be taken with Stivits Vitamin C 1000 mg.
Yes, zinc and copper can be taken together. In studies, zinc lowered copper at 50 mg a day or more for weeks; that is where copper is affected, not a safe level. Seven Stivits products contain zinc and copper together, at up to 20 mg of zinc per daily serving. Add up the zinc from all your Stivits products and do not combine several zinc products without asking a doctor or pharmacist.
Yes. Iron at 25 mg or more lowers zinc absorption somewhat, but a 2005 review found no reason to avoid taking them together. Stivits Iron Complex contains 27 mg of iron and 10 mg of zinc in one tablet.
No. The role of vitamin K alongside vitamin D is unclear, according to the NIH Office of Dietary Supplements. Vitamin D contributes to the normal absorption/utilisation of calcium and phosphorus on its own. A varied and balanced diet and a healthy lifestyle are important. Stivits sells D3 and K2 separately and as one tablet.
No. The idea came from early laboratory work; later studies in 1976 and 1980 traced the result to a flaw in the measuring method. Stivits Vitamin C 1000 mg and Stivits B12 products can be taken on the same day.
Take psyllium ½–1 hour apart from other supplements, with plenty of water. This follows the European Medicines Agency herbal monograph EMA/HMPC/199774/2012. It applies to Stivits Psyllium Husk, GASTROPSYL and Detox Formula.
Yes, but take them at different times of day. Stivits Multivitamins and Minerals contains 260 mg of calcium, which lowers iron absorption from the same dose. Stivits Iron Complex contains 27 mg of iron.
We found no documented interaction between melatonin and valerian in the sources we checked, but absence of evidence is not proof of safety. The US National Center for Complementary and Integrative Health advises against combining valerian with sedative medicines. If you take any medicines, ask a doctor or pharmacist before combining Stivits Melatonin 1 mg with Stivits Valerian root.