Citrus magnesium, commonly known as magnesium citrate, is a widely used supplement combining elemental magnesium with citric acid, often flavoured with citrus for improved taste. Whilst generally well tolerated, citrus magnesium side effects can occur, particularly affecting the digestive system. Understanding these potential adverse effects, recognising when they require medical attention, and knowing how to minimise them is essential for safe supplementation. This article examines the common and serious side effects of magnesium citrate, identifies who should avoid it, and provides practical guidance on reducing unwanted reactions whilst benefiting from this important mineral supplement.

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. This formulation is often marketed with citrus flavouring to improve palatability. Magnesium citrate may have better absorption than some other magnesium salts, though results vary between studies. It's available over-the-counter in various forms including tablets, capsules, powders, and liquid preparations.

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 common use for relieving constipation.

In the UK, magnesium citrate is used both as a dietary supplement to address magnesium deficiency and as a bowel preparation agent before certain medical procedures. The Reference Nutrient Intake (RNI) for magnesium varies by age and gender, with adult men requiring approximately 300mg and women 270mg daily according to NHS guidance. When taken as a supplement, typical doses range from 200-400mg of elemental magnesium daily. From supplements alone, 400mg/day or less is unlikely to cause harm (NHS); higher intakes should only be taken under clinical supervision.

The citrate form is commonly chosen for supplementation, though different magnesium compounds may be preferred for specific purposes or individual tolerability.

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.

Drowsiness can occasionally occur at higher doses, as magnesium has natural muscle-relaxing properties. This is uncommon at standard supplemental doses but may be noticed by sensitive individuals.

These 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 or when magnesium citrate is specifically used as a laxative. Most individuals tolerate standard supplemental doses well, particularly when introduced gradually and taken with meals.

If diarrhoea occurs, ensure you replace lost fluids by drinking plenty of water. 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, as the kidneys are responsible for excreting excess magnesium. Early signs of hypermagnesaemia include nausea, vomiting, flushing, hypotension, and lethargy, progressing to more serious manifestations in severe cases.

Call 999 or go to A&E immediately if you experience:

• Significant difficulty breathing or shortness of breath

• Severe muscle weakness or paralysis

• Confusion, extreme drowsiness, or altered mental state

• Signs of allergic reaction including facial swelling, throat tightness, or severe dizziness

• Irregular heartbeat, bradycardia (slow heart rate), or collapse

Contact NHS 111 or your GP urgently if you experience:

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

• Severe abdominal pain

• Rectal bleeding – this is not a direct effect of magnesium but requires prompt medical assessment

• Persistent vomiting or inability to keep fluids down

Individuals with kidney disease are at substantially higher risk of magnesium accumulation and should only take magnesium supplements under close medical supervision. Similarly, those taking certain medications (particularly those affecting kidney function or electrolyte balance) 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. They can assess whether the symptoms are related to magnesium citrate, evaluate for potential interactions with other medications, and recommend appropriate management strategies.

Suspected adverse reactions can be reported to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

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 – magnesium can interfere with neuromuscular transmission and potentially worsen muscle weakness

• Heart block or severe cardiac conduction disorders – magnesium affects cardiac electrical activity

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

• Children – should not take adult magnesium supplements unless specifically advised by a healthcare professional; dosing is product-specific

Pregnant and breastfeeding women should consult their midwife or GP before taking magnesium citrate supplements, although magnesium is generally considered safe during pregnancy at appropriate doses. The NHS advises that dietary intake is usually sufficient, and supplementation should only be undertaken with professional guidance. For constipation during pregnancy, macrogol (polyethylene glycol) laxatives are often recommended as first-line treatment.

Drug interactions are an important consideration. Magnesium citrate can interfere with the absorption of certain medications including:

• Levothyroxine – separate by at least 4 hours

• Bisphosphonates (osteoporosis treatments) – separate according to the specific product guidance

• Tetracycline and quinolone antibiotics – separate by 2-6 hours depending on the specific antibiotic

• Iron supplements – separate by at least 2 hours

Magnesium may also affect the activity of certain blood pressure medications. Always inform your GP and pharmacist about all supplements you are taking.

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

• Take in the evening – if drowsiness occurs, bedtime dosing can be beneficial

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

• Check product labelling – look for 'elemental magnesium' content when calculating your daily intake

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. Different magnesium compounds may vary in their digestive system effects.

Dietary considerations can enhance tolerance. Taking magnesium citrate with a moderate meal rather than on an empty stomach often improves tolerance. Similarly, limiting caffeine and alcohol intake can reduce gastrointestinal irritation.

If diarrhoea persists despite these measures, consider alternative magnesium forms such as magnesium glycinate, which is generally gentler on the digestive system for many people. Discuss options with your pharmacist or GP.

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. If you require magnesium supplementation for a specific deficiency confirmed by blood tests, your GP can help ensure therapeutic levels are achieved without excessive intake. Remember that most side effects are preventable or manageable with appropriate dosing and administration techniques.

If you experience any concerning side effects, report them to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Frequently Asked Questions