Maximize Your Intake: What should you not take with magnesium?

October 23, 2025 •

5 min read

It is estimated that up to 50% of the U.S. population consumes less than the recommended daily allowance for magnesium. To ensure your body can properly absorb and utilize this vital mineral, it's crucial to understand what you should not take with magnesium, as certain substances can hinder its effectiveness and lead to poor health outcomes.

Quick Summary

Certain foods high in oxalates and phytates, along with beverages containing caffeine, alcohol, and phosphoric acid, can impede magnesium absorption. High doses of other minerals like calcium and iron can create competition for uptake. Several medications also interact with magnesium, necessitating careful timing to maximize benefits and avoid complications.

Key Points

Avoid High-Dose Calcium: Large amounts of calcium can compete with magnesium for intestinal absorption, so space out your doses of these two minerals by a few hours.
Separate High-Dose Iron: Iron and magnesium can interfere with each other's absorption, especially in high doses. Take them at different times of the day for optimal efficacy.
Mind Oxalate-Rich Foods: Compounds in foods like spinach and beets can bind to magnesium. Consume these foods separately from your supplement intake to maximize absorption.
Limit Caffeine and Alcohol: Both caffeine and alcohol are diuretics that increase magnesium excretion. It's best to separate their consumption from your magnesium supplement by at least one to two hours.
Be Cautious with Specific Medications: Certain antibiotics, bisphosphonates, and PPIs can affect magnesium absorption or levels. Always consult your doctor or pharmacist about timing and potential interactions.
Prefer Well-Absorbed Forms: Opt for magnesium supplements like citrate or glycinate, which are generally better absorbed by the body than less bioavailable forms like magnesium oxide.
Strategize Supplement Timing: Taking magnesium in the evening may aid sleep, while separating conflicting nutrients like calcium and iron is crucial for overall absorption.

Why Magnesium Absorption Matters

Magnesium is an essential mineral involved in over 300 biochemical reactions in the body, supporting everything from nerve and muscle function to heart health and energy production. However, the amount of magnesium absorbed from food and supplements can be highly variable, with some estimates suggesting that only 35-40% of dietary magnesium is typically absorbed. This rate can be further compromised by specific foods, drinks, other supplements, and medications. Knowing how these substances interact with magnesium is key to optimizing your intake, whether from diet or supplements.

Foods and Compounds That Impede Absorption

Several naturally occurring compounds in food can bind to magnesium in the digestive tract, making it less available for absorption. Separating your magnesium intake from these items can be a simple but effective strategy.

Oxalates: Found in high concentrations in certain foods like spinach, rhubarb, and beets, oxalates can bind to minerals, including magnesium. Research has shown that magnesium absorption was significantly lower from a meal with spinach compared to one with low-oxalate greens like kale. Cooking these vegetables can help reduce their oxalate content, but for optimal absorption, it's still best to time your supplement dose away from a large meal containing these foods.
Phytates: Present in whole grains, beans, and nuts, phytic acid can also chelate, or bind, to minerals. While phytates primarily affect iron and zinc, they can also slightly interfere with magnesium uptake. Soaking, sprouting, or fermenting beans and grains can help reduce their phytate levels.
Insoluble Fiber: While fermentable (soluble) fiber may actually enhance magnesium absorption, large quantities of insoluble fiber from sources like bran can reduce the amount of magnesium your body absorbs. It is recommended to space out high-fiber supplements and magnesium doses by at least two hours.

Beverages to Avoid with Magnesium

Certain drinks can either interfere directly with absorption or cause an increase in magnesium excretion from the body.

Caffeine: As a mild diuretic, caffeine can increase urinary excretion of magnesium, potentially reducing the mineral's overall retention. For best results, allow at least one to two hours between consuming caffeinated beverages like coffee or tea and taking your magnesium supplement.
Alcohol: Chronic alcohol consumption can negatively impact magnesium in multiple ways. It increases urinary loss, reduces absorption in the gut, and can impair kidney function. Heavy drinking is strongly associated with low magnesium levels and can undermine the effectiveness of supplementation.
Carbonated Drinks: Colas and other soft drinks contain phosphoric acid. This compound can increase magnesium loss through the kidneys, and the high sodium content of some sodas can exacerbate this effect.

Potential Interactions with Other Supplements and Minerals

Some essential minerals compete with magnesium for absorption pathways in the digestive system. Balancing your intake is crucial for maximizing the benefits of each.

High-Dose Calcium: Although magnesium aids calcium absorption, taking them together in high doses can lead to competition. A calcium-to-magnesium ratio higher than 2:1 is linked to certain metabolic risks. To prevent this competition, separate your calcium and magnesium supplements by at least a few hours.
High-Dose Iron: Iron can inhibit magnesium absorption, and vice versa, as they use similar transport mechanisms in the gut. For optimal efficacy of both, it is best to take them at separate times of the day—for example, iron in the morning and magnesium in the evening.
High-Dose Zinc: While low doses of zinc and magnesium can be taken together, high-dose zinc supplementation can interfere with magnesium absorption. For best results, space out high-dose zinc supplements from your magnesium.

Medications That Interact with Magnesium

Several types of prescription and over-the-counter medications can affect magnesium levels, either by reducing absorption or increasing excretion. Always consult a healthcare provider when taking supplements alongside medication.

Antibiotics: Certain antibiotics, particularly tetracyclines (e.g., doxycycline) and quinolones (e.g., ciprofloxacin), can form complexes with magnesium in the stomach, rendering both the antibiotic and the magnesium less effective. To prevent this, separate your antibiotic and magnesium dose by at least two hours.
Bisphosphonates: Used to treat osteoporosis, bisphosphonate medications (e.g., alendronate) can have their absorption reduced by magnesium. Taking them at least two hours apart is recommended.
Proton Pump Inhibitors (PPIs): Long-term use of PPIs (e.g., omeprazole, lansoprazole) can lead to low magnesium levels by impairing absorption. Patients on long-term PPI therapy may need to monitor their magnesium status.
Diuretics: Certain diuretics, such as loop and thiazide diuretics, can increase the loss of magnesium through urine. Conversely, potassium-sparing diuretics may increase magnesium levels. It is important to discuss your magnesium intake with your doctor if you are on diuretic therapy.

Comparison of Magnesium Interactions


Substance	Type of Interaction	Recommended Action
High-Dose Calcium	Competes for absorption pathways	Separate doses by at least a few hours.
High-Dose Iron	Competes for absorption mechanisms	Take at different times (e.g., iron in the morning, magnesium at night).
High-Dose Zinc	Can reduce absorption in high amounts	If taking high doses, separate intake.
Oxalate-Rich Foods	Binds to magnesium, reducing absorption	Consume away from supplement time; cooking helps.
Phytate-Rich Foods	Binds to minerals, including magnesium	Soak or sprout grains/beans; time supplements accordingly.
Caffeine	Acts as a diuretic, increasing excretion	Space intake by 1-2 hours.
Alcohol	Increases excretion and impairs gut absorption	Limit consumption, especially around supplementation.
Antibiotics	Forms complexes that reduce absorption	Separate doses by at least 2 hours.
PPIs	Long-term use can reduce absorption	Discuss monitoring magnesium levels with a doctor.

Conclusion: Optimizing Your Magnesium Intake

Magnesium is a cornerstone of good health, but its benefits can be maximized by being mindful of what you consume alongside it. By strategically timing your intake and avoiding known inhibitors, you can significantly improve the absorption and effectiveness of your magnesium supplements. Remember to consult a healthcare provider before beginning any new supplement regimen, especially if you are taking medications. Prioritizing these practices will ensure you get the most out of this crucial mineral and support your overall well-being. For a comprehensive guide on supplements, including magnesium, consult authoritative sources like the NIH Office of Dietary Supplements.

Additional Considerations for Magnesium Supplementation

Choosing the right form of magnesium, such as citrate or glycinate, can also enhance bioavailability compared to less-absorbed forms like magnesium oxide. Spacing your daily dose into smaller amounts may also improve tolerance and absorption, particularly for higher doses. While a balanced diet is the best source of nutrients, these targeted strategies for supplementation can help close any nutritional gaps and prevent negative interactions that may hinder magnesium's benefits.

Frequently Asked Questions

While magnesium helps regulate calcium, taking high doses of both at the same time can cause competition for absorption in the intestines. It is generally recommended to separate your intake by at least a few hours to ensure proper absorption of both minerals.

Spinach contains oxalates, which can bind to magnesium and reduce its absorption. While you shouldn't avoid these healthy foods entirely, consider taking your magnesium supplement away from a meal that heavily features them. Cooking can also help reduce oxalate levels.

Yes, caffeine acts as a mild diuretic and can increase the excretion of magnesium through urine. To minimize this effect, it's best to wait at least one to two hours after drinking coffee or tea before taking your magnesium supplement.

Yes, certain medications like some antibiotics (e.g., tetracyclines, quinolones), osteoporosis drugs (bisphosphonates), and long-term use of proton pump inhibitors (PPIs) can interfere with magnesium absorption or levels. Always discuss supplementation with your doctor or pharmacist.

Both iron and magnesium compete for similar absorption pathways in the digestive tract, which can reduce the effectiveness of both. It is best to take these supplements at different times of the day to ensure optimal absorption for each.

High-dose zinc can compete with magnesium for absorption, potentially reducing its effectiveness. While small amounts in a multivitamin are usually fine, separate high-dose zinc supplements from your magnesium dose.

To improve absorption, take your supplement with a meal to enhance bioavailability and minimize stomach discomfort. Also, choose well-absorbed forms like magnesium glycinate or citrate, and consistently take your supplement while spacing it out from conflicting substances.