Citrus magnesium, commonly known as magnesium citrate, is a widely used supplement combining elemental magnesium with citric acid. Valued for its good bioavailability, it supports over 300 enzymatic reactions in the body, including muscle function, cardiovascular health, and energy production. Whilst generally well-tolerated, magnesium citrate can cause side effects, particularly affecting the gastrointestinal system. Understanding these potential adverse effects, recognising warning signs, and knowing who should avoid supplementation is essential for safe use. This article examines the common and serious side effects of citrus magnesium, identifies at-risk groups, and provides practical guidance for minimising adverse reactions whilst maintaining therapeutic benefit.

What Is Citrus Magnesium and How Does It Work?

Citrus magnesium typically refers to magnesium citrate, a widely used form of magnesium supplement that combines elemental magnesium with citric acid (not simply citrus-flavoured products). This formulation is valued for its relatively good bioavailability compared to some other magnesium salts, meaning the body can absorb and utilise it more efficiently. Magnesium citrate is available over-the-counter in various forms including tablets, capsules, powders, and liquid preparations, often with added citrus flavouring to improve palatability.

Magnesium is an essential mineral involved in over 300 enzymatic reactions throughout the body. It plays crucial roles in muscle and nerve function, blood glucose control, protein synthesis, and bone health. The citrate form works through multiple mechanisms: it helps maintain normal muscle contraction and relaxation, supports cardiovascular function by regulating heart rhythm, and contributes to energy production at the cellular level. Additionally, magnesium citrate has osmotic laxative properties, drawing water into the intestines, which explains its use for relieving constipation.

In the UK, magnesium citrate is used both as a dietary supplement to address magnesium deficiency and as an ingredient in licensed bowel-cleansing products (often combined with other substances) before certain medical procedures. The NHS recommended daily intake for magnesium is approximately 300mg for men and 270mg for women. When taken as a supplement, typical doses range from 200-400mg of elemental magnesium daily. The NHS advises not exceeding 400mg of supplemental magnesium per day unless under medical supervision.

When purchasing supplements, it's important to check labels carefully to distinguish between the total weight of the compound and the amount of elemental magnesium it contains. Different magnesium formulations contain varying percentages of elemental magnesium, which is the active component.

Common Side Effects of Citrus Magnesium

The most frequently reported side effects of magnesium citrate involve the gastrointestinal system, largely due to its osmotic properties and the body's limited capacity to absorb large amounts of magnesium at once. Diarrhoea is the most common adverse effect, occurring when magnesium draws excess water into the intestinal tract. This effect is dose-dependent and typically develops within hours of ingestion, particularly when taking higher doses or when first starting supplementation.

Other common gastrointestinal side effects include:

• Abdominal cramping and discomfort – often mild to moderate and usually temporary

• Nausea – particularly when taken on an empty stomach or in liquid form

• Bloating and flatulence – resulting from altered gut motility

• Loose stools – even at therapeutic doses in sensitive individuals

Some people experience a metallic or bitter taste in the mouth, especially with liquid formulations. This is generally harmless but can be unpleasant. Taking the supplement with food or diluting liquid preparations may help reduce this effect.

These common side effects are typically mild and self-limiting, often resolving as the body adjusts to supplementation. They are more likely to occur with higher doses (above 400mg elemental magnesium daily) or when magnesium citrate is specifically used as a laxative at therapeutic doses. Most individuals tolerate standard supplemental doses well, particularly when introduced gradually and taken with meals.

The NHS advises not exceeding 400mg of supplemental magnesium per day, as higher doses commonly cause diarrhoea. If gastrointestinal symptoms persist beyond the first week of use or significantly impact daily activities, it is advisable to reduce the dose or consult a healthcare professional about alternative magnesium formulations.

Serious Side Effects and When to Seek Medical Help

Whilst serious adverse effects from magnesium citrate supplementation are uncommon in individuals with normal kidney function, hypermagnesaemia (elevated blood magnesium levels) can occur and potentially become life-threatening. This condition is most likely in people with impaired renal function, especially those with moderate to severe chronic kidney disease (eGFR <60, particularly <30 mL/min/1.73m²), as the kidneys are responsible for excreting excess magnesium. Early symptoms of magnesium toxicity include severe diarrhoea, nausea, and vomiting, which can progress to more serious manifestations.

Seek immediate medical attention (call 999 or go to A&E) if you experience any of the following:

• Severe or persistent diarrhoea lasting more than 48 hours, particularly if accompanied by dehydration signs (extreme thirst, reduced urination, dizziness)

• Irregular heartbeat or palpitations – magnesium affects cardiac conduction and excessive levels can cause arrhythmias

• Difficulty breathing or shortness of breath – indicating possible respiratory muscle weakness

• Severe muscle weakness or loss of reflexes

• Confusion, drowsiness, or altered mental state – suggesting significant electrolyte imbalance

• Severe abdominal pain or rectal bleeding

Allergic reactions to magnesium citrate are rare but possible. Signs include rash, itching, swelling (particularly of the face, tongue, or throat), severe dizziness, and difficulty breathing. Any suspected allergic reaction requires emergency medical assessment.

Individuals with kidney disease should avoid magnesium supplements unless specifically prescribed and monitored by a nephrologist or specialist. It's also important to review all sources of magnesium (including antacids, laxatives, and other supplements) to avoid cumulative intake.

Those taking certain medications (particularly those affecting kidney function or electrolyte balance, such as ACE inhibitors, ARBs, or potassium-sparing diuretics) should consult their GP before starting magnesium supplementation.

If you develop persistent symptoms that interfere with daily activities, or if common side effects do not improve after adjusting the dose or timing, contact your GP or pharmacist for advice. You can also report any suspected side effects to the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).

Who Should Avoid Citrus Magnesium?

Certain individuals should exercise caution or avoid magnesium citrate supplementation altogether due to increased risk of adverse effects or complications. People with kidney disease or impaired renal function represent the highest-risk group, as reduced kidney capacity to excrete magnesium can lead to dangerous accumulation. This includes those with chronic kidney disease (CKD) at any stage, acute kidney injury, or significantly reduced glomerular filtration rate (GFR). These individuals should only take magnesium supplements if specifically prescribed and monitored by a nephrologist or specialist.

Contraindications and cautions include:

• Bowel obstruction or suspected intestinal blockage – magnesium citrate's laxative effect could worsen the condition

• Severe inflammatory bowel disease during acute flares – may exacerbate diarrhoea and electrolyte imbalances

• Myasthenia gravis – high magnesium levels can interfere with neuromuscular transmission

• Heart block or severe cardiac conduction disorders – particularly if at risk of hypermagnesaemia

• Severe dehydration or electrolyte imbalances – should be corrected before starting supplementation

Pregnant and breastfeeding women should consult their midwife or GP before taking magnesium citrate supplements. Magnesium is generally considered safe during pregnancy at appropriate doses, and dietary intake is usually sufficient. Supplementation should only be undertaken with professional guidance.

Drug interactions are an important consideration. Magnesium citrate can interfere with the absorption of certain medications. Specific spacing is recommended:

• Bisphosphonates (osteoporosis treatments): Take bisphosphonate on an empty stomach; avoid magnesium the same morning

• Tetracyclines and quinolone antibiotics: Separate by 2-4 hours

• Thyroid medications (levothyroxine): Take at least 4 hours apart

• Iron supplements: Separate by at least 2 hours

• Some HIV medications (e.g., dolutegravir): Separate by several hours

Children and adolescents should not use magnesium salts as laxatives without medical advice.

Older adults may be more susceptible to side effects and should start with lower doses. Those with multiple chronic conditions or taking several medications require careful assessment before beginning magnesium supplementation to avoid potential interactions or complications.

How to Minimise Side Effects When Taking Citrus Magnesium

Several practical strategies can help reduce the likelihood and severity of side effects when taking magnesium citrate supplements. Starting with a lower dose and gradually increasing over one to two weeks allows the digestive system to adapt and helps identify your individual tolerance level. Begin with 100-200mg of elemental magnesium daily, even if your target dose is higher, and increase incrementally every few days as tolerated.

Timing and administration techniques can significantly impact side effects:

• Take with food – consuming magnesium citrate with meals slows absorption and reduces gastrointestinal irritation

• Divide the daily dose – splitting your total dose into two or three smaller amounts throughout the day improves tolerance and absorption

• Stay well-hydrated – adequate fluid intake helps prevent excessive laxative effects and supports kidney function

• Separate from interacting medicines – follow specific timing guidance for antibiotics, thyroid medications, bisphosphonates and other interacting medicines

Choosing the right formulation matters. If liquid preparations cause nausea or taste issues, tablets or capsules may be better tolerated. Conversely, some people find powders mixed into beverages easier on the stomach. Some individuals report better tolerance with different magnesium forms (such as magnesium glycinate), though individual responses vary.

Dietary considerations can enhance tolerance. If diarrhoea occurs, try taking magnesium with a smaller or low-fibre meal initially. Similarly, limiting caffeine and alcohol intake can reduce gastrointestinal irritation.

Monitor your response by keeping a brief diary of symptoms, timing, and dosage for the first few weeks. This information helps identify patterns and optimal dosing strategies. Remember to check all sources of magnesium (including antacids, laxatives, and multivitamins) to avoid exceeding the recommended intake.

Always adhere to the NHS guidance not to exceed 400mg of supplemental elemental magnesium daily unless medically supervised, and never use over-the-counter magnesium supplements for bowel preparation before medical procedures – only use licensed products as directed by healthcare professionals.

If you require magnesium supplementation for a specific deficiency confirmed by blood tests, regular monitoring by your GP ensures therapeutic levels are achieved without excessive intake.

Frequently Asked Questions