Can you take calcium and magnesium together? Yes, these essential minerals can be safely combined in your supplement routine. Calcium and magnesium are often formulated together and play complementary roles in bone health, muscle function, and metabolic processes. Whilst they may compete for absorption at very high doses, this does not preclude concurrent use. In the UK, healthcare professionals typically assess dietary intake first, recommending supplements only when diet is insufficient. Individual requirements vary based on age, gender, dietary habits, and underlying health conditions. Before starting any supplement regimen, consult your GP or registered dietitian, particularly if you have existing medical conditions, are pregnant or breastfeeding, or take medications that might interact with these minerals.

Can You Take Calcium and Magnesium Together?

Yes, calcium and magnesium can be taken together, and many people do so safely as part of their daily supplement routine. These two essential minerals are often combined in a single supplement formulation, and there is no official contraindication to taking them concurrently. Both minerals play vital roles in maintaining bone health, muscle function, and numerous metabolic processes throughout the body.

However, it is important to understand that calcium and magnesium can compete for absorption in the digestive tract when taken in very high doses at the same time. This potential interaction does not mean they cannot be taken together, but rather that attention should be paid to dosage and timing. The body requires both minerals for optimal function, and deficiency in either can lead to significant health consequences.

The decision to take calcium and magnesium together should ideally be based on individual requirements, which may vary depending on dietary intake, age, gender, and underlying health conditions. In the UK, healthcare professionals typically assess dietary calcium intake first and recommend supplements only when diet is insufficient. For bone health, the focus is usually on ensuring adequate calcium and vitamin D rather than routine magnesium co-supplementation. Before starting any supplement regimen, it is advisable to discuss your specific needs with a GP or registered dietitian, particularly if you have existing medical conditions, are pregnant or breastfeeding, or take other medications that might interact with these minerals.

How Calcium and Magnesium Work in the Body

Calcium is the most abundant mineral in the human body, with approximately 99% stored in bones and teeth, where it provides structural support and strength. The remaining 1% circulates in blood and soft tissues, playing critical roles in muscle contraction, nerve transmission, blood clotting, and enzyme function. Calcium homeostasis is tightly regulated by parathyroid hormone (PTH), vitamin D, and calcitonin, which work together to maintain serum calcium levels within a narrow physiological range.

Magnesium, the fourth most abundant mineral in the body, is involved in over 300 enzymatic reactions. Approximately 50-60% of the body's magnesium is stored in bone, whilst the remainder is found in soft tissues and a small amount in extracellular fluid. Magnesium is essential for energy production (ATP synthesis), protein synthesis, DNA and RNA synthesis, and the regulation of neuromuscular function. It also plays a crucial role in maintaining normal heart rhythm and supporting immune function.

The relationship between calcium and magnesium is complex and interdependent. Magnesium is required for the proper metabolism and utilisation of calcium, including the activation of vitamin D, which in turn enhances calcium absorption. Magnesium also influences the secretion and action of PTH, the primary regulator of calcium homeostasis. Conversely, adequate calcium status can affect magnesium balance. These minerals work synergistically in muscle contraction and relaxation: calcium triggers muscle contraction, whilst magnesium promotes relaxation. This balance is particularly important in cardiac and smooth muscle function, where disruption can lead to cramping, spasms, or arrhythmias.

Benefits of Taking Calcium and Magnesium Together

Both calcium and magnesium are essential for bone health, though in the UK, guidance focuses primarily on ensuring adequate calcium and vitamin D intake for bone health maintenance. Calcium is a key component of bone matrix, and adequate intake is associated with improved bone mineral density and reduced risk of osteoporosis. Research suggests that magnesium deficiency may impair calcium metabolism and contribute to bone fragility, even when calcium intake is adequate. However, it's important to note that routine combined calcium and magnesium supplementation is not specifically recommended in UK clinical guidelines for osteoporosis prevention.

Regarding cardiovascular health, the evidence for combined supplementation remains inconclusive. Magnesium helps regulate vascular tone and blood pressure, whilst calcium is involved in cardiac muscle contraction. Some observational studies suggest associations between magnesium status and cardiovascular outcomes, but there is no established UK recommendation for a specific calcium-to-magnesium ratio in the diet or from supplements. Current evidence does not support routine magnesium supplementation for cardiovascular prevention in the general population.

For muscle function and neuromuscular health, the complementary roles of calcium (contraction) and magnesium (relaxation) in muscle physiology mean that deficiency in either mineral can lead to muscle cramps, spasms, or weakness. Athletes and older adults, who may be at higher risk of deficiencies, might benefit from ensuring adequate intake of both minerals. Some individuals report improvements in sleep quality and reduction in symptoms of restless legs syndrome with magnesium supplementation, though robust clinical evidence for these effects is limited. As with all supplements, benefits should be weighed against individual needs and potential risks, with a focus on addressing confirmed deficiencies rather than speculative benefits.

Recommended Dosages and Timing

The recommended daily intake for calcium in the UK is 700 mg for adults aged 19-64, which can typically be obtained through a balanced diet including dairy products, fortified plant-based alternatives, green leafy vegetables, and fish with edible bones. For bone health, UK guidance (including from the National Osteoporosis Guideline Group) recommends assessing dietary calcium intake first and supplementing only if diet is insufficient to achieve adequate total intake. When supplementation is needed, it should be tailored to fill the gap between dietary intake and requirements, rather than routinely prescribing high doses.

For magnesium, the UK Reference Nutrient Intake (RNI) is 300 mg for men and 270 mg for women aged 19-64. Dietary sources include nuts, seeds, whole grains, legumes, and green leafy vegetables. When supplementation is necessary, doses typically range from 200-400 mg daily. The UK Expert Group on Vitamins and Minerals advises that supplemental magnesium up to 400 mg daily is unlikely to cause harm, though it can cause diarrhoea due to its osmotic effect.

Regarding timing and absorption considerations, there is no officially recommended ratio of calcium to magnesium intake in the UK. To maximise absorption, consider the following strategies: take calcium supplements in divided doses of no more than 500 mg at a time, as absorption efficiency decreases with larger single doses; calcium carbonate is best absorbed with food, whilst calcium citrate can be taken with or without food; magnesium supplements are generally well absorbed and can be taken with meals to reduce gastrointestinal side effects. If taking high doses of both minerals, spacing them several hours apart may improve absorption, though this is not always necessary at standard supplementation levels. Always follow the specific instructions provided with your supplement or as advised by your healthcare professional.

Potential Interactions and Side Effects

Whilst generally safe when taken at recommended doses, calcium and magnesium supplements can cause side effects and interact with various medications. Common adverse effects of calcium supplementation include constipation, bloating, and gastrointestinal discomfort. Excessive calcium intake (above 1,500 mg daily from supplements) may increase the risk of kidney stones in susceptible individuals and has been associated with cardiovascular concerns in some studies, though evidence remains inconclusive. Magnesium supplements commonly cause loose stools or diarrhoea, particularly at doses exceeding 400 mg daily, due to magnesium's osmotic effect in the intestine.

Important drug interactions must be considered. Calcium can significantly reduce the absorption of several medications, including:

• Bisphosphonates (e.g., alendronic acid for osteoporosis) – should be taken at least 30 minutes before calcium

• Levothyroxine (thyroid hormone replacement) – separate by at least 4 hours

• Certain antibiotics (tetracyclines, quinolones) – separate by 2-3 hours before or 4-6 hours after taking these antibiotics

• Iron supplements – calcium inhibits iron absorption; separate by at least 2 hours

Magnesium can interact with:

• Bisphosphonates – reducing their absorption

• Certain antibiotics (tetracyclines, quinolones) – forming complexes that reduce effectiveness

• Diuretics – some increase magnesium loss, whilst others (potassium-sparing types) may increase magnesium retention

Long-term use of proton pump inhibitors (PPIs) can cause hypomagnesaemia (low blood magnesium), as highlighted in MHRA Drug Safety Updates. If you take PPIs and develop symptoms like muscle cramps or weakness, your GP may check your magnesium levels.

Individuals with impaired kidney function should exercise particular caution, as the kidneys regulate mineral excretion. Accumulation of calcium or magnesium can occur in chronic kidney disease, potentially leading to serious complications including hypercalcaemia or hypermagnesaemia. Always inform your GP and pharmacist about all supplements you are taking to avoid potentially harmful interactions.

When to Seek Medical Advice

Consult your GP before starting calcium and magnesium supplements if you have any of the following conditions: chronic kidney disease, parathyroid disorders, heart rhythm abnormalities, kidney stones (current or previous), sarcoidosis, or any condition affecting calcium metabolism. Individuals taking multiple medications should also seek professional advice to assess potential interactions and ensure safe supplementation. If you are pregnant or breastfeeding, speak with your GP, midwife or pharmacist before starting any supplements, as your requirements may differ.

Call 999 or go to A&E immediately if you experience symptoms that may indicate serious mineral imbalance, including:

• Severe muscle weakness or paralysis

• Irregular heartbeat or palpitations

• Severe abdominal pain or persistent vomiting

• Confusion or altered mental state

• Extreme fatigue or lethargy

• Difficulty breathing

• Chest pain

These symptoms could indicate hypercalcaemia (excess calcium) or hypermagnesaemia (excess magnesium), both of which require prompt medical assessment. Hypercalcaemia may also cause increased thirst and frequent urination.

Contact your GP for routine advice if you experience: persistent constipation or diarrhoea after starting supplements, symptoms suggestive of deficiency (such as muscle cramps, tingling, or bone pain) despite supplementation, or if you are unsure about appropriate dosing for your individual circumstances. For urgent concerns that aren't life-threatening, contact NHS 111 for advice.

Regular monitoring may be appropriate for certain groups, including older adults on long-term supplementation, individuals with malabsorption conditions (such as coeliac disease or inflammatory bowel disease), and those taking medications that affect mineral metabolism. A registered dietitian can provide personalised advice on optimising mineral intake through diet and appropriate supplementation. If you experience any suspected side effects from supplements, report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk). Remember that supplements should complement, not replace, a balanced diet rich in calcium and magnesium from natural food sources.

Frequently Asked Questions