Citrus magnesium side effects primarily involve the gastrointestinal system, with diarrhoea being the most common adverse reaction. Magnesium citrate, often referred to colloquially as 'citrus magnesium', is a widely used supplement combining elemental magnesium with citric acid. Whilst generally well-tolerated at recommended doses, its osmotic properties can cause abdominal cramping, nausea, and loose stools, particularly when starting supplementation or taking higher doses. Serious side effects such as hypermagnesaemia are uncommon in people with normal kidney function but can be life-threatening in those with renal impairment. Understanding potential adverse effects and how to minimise them helps ensure safe, effective use of this popular mineral supplement.

What Is Magnesium Citrate and How Does It Work?

Magnesium citrate (sometimes colloquially called 'citrus magnesium') is a widely used form of magnesium supplement that combines elemental magnesium with citric acid. This formulation has good bioavailability compared to other magnesium salts, meaning the body can absorb and utilise it relatively 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, though macrogols (polyethylene glycol) are typically first-line laxatives in UK practice.

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 (as licensed medicines such as Citramag). The recommended daily allowance 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. The NHS advises that taking up to 400mg of magnesium daily from supplements is unlikely to cause harm, and higher doses should only be taken under healthcare professional supervision.

The citrate form is generally well-absorbed compared to some other magnesium compounds, though this enhanced bioavailability can also contribute to certain side effects, particularly gastrointestinal symptoms.

Common Side Effects of Magnesium Citrate

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 over several days to weeks. The gastrointestinal effects are generally more pronounced when magnesium citrate is used specifically as a laxative at higher doses compared to standard supplementation doses. When used for bowel preparation before procedures, always follow the specific instructions provided with the licensed product or by your healthcare professional.

It's worth noting that individual tolerance varies considerably. Some people can take standard doses without difficulty, whilst others experience symptoms at relatively low intakes. If you experience persistent diarrhoea, you should stop or reduce the dose and ensure you maintain adequate hydration. Starting with a lower dose and gradually increasing can help identify your personal tolerance threshold.

Serious Side Effects and When to Seek Medical Help

Whilst serious adverse effects from magnesium citrate are uncommon in people with normal kidney function, hypermagnesaemia (excessively high blood magnesium levels) can occur and potentially become life-threatening. This condition is most likely to develop in individuals with impaired renal function, as the kidneys are responsible for excreting excess magnesium.

Early warning signs of magnesium toxicity include:

• Severe or persistent diarrhoea leading to dehydration

• Significant muscle weakness or loss of reflexes

• Irregular heartbeat or palpitations

• Difficulty breathing or shortness of breath

• Confusion, dizziness, or altered mental state

• Severe nausea and vomiting

As hypermagnesaemia progresses, more serious symptoms can develop including profound hypotension (dangerously low blood pressure), bradycardia (abnormally slow heart rate), and in severe cases, cardiac arrest or respiratory paralysis. These represent medical emergencies requiring immediate hospital treatment.

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

• Chest pain, severe palpitations, or feeling faint

• Extreme weakness or inability to move muscles normally

• Severe, uncontrolled diarrhoea with signs of dehydration (dark urine, extreme thirst, reduced urination)

• Difficulty breathing or swallowing

• Allergic reactions such as facial swelling, hives, or throat tightness

Contact your GP promptly if:

• Gastrointestinal side effects persist beyond one week

• You develop persistent abdominal pain

• Side effects significantly impact your daily activities

• You're taking other medications and notice new symptoms

According to NICE Clinical Knowledge Summaries, patients presenting with suspected electrolyte disturbance should have urgent blood tests including serum magnesium, renal function, and ECG monitoring if cardiac symptoms are present. Treatment for magnesium toxicity typically includes intravenous calcium gluconate, fluid resuscitation, and in severe cases, dialysis to remove excess magnesium from the bloodstream.

If you suspect a side effect from a medicine, you can report it via the MHRA Yellow Card scheme.

Who Should Avoid Magnesium Citrate?

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 are at highest risk, as reduced kidney capacity to excrete magnesium can lead to dangerous accumulation. Anyone with an estimated glomerular filtration rate (eGFR) below 30 mL/min/1.73m² should generally avoid magnesium supplements unless specifically prescribed and monitored by a nephrologist.

Individuals with the following conditions should consult their GP before taking magnesium citrate:

• Heart block or other cardiac conduction disorders – magnesium can further slow electrical conduction in the heart

• Myasthenia gravis – magnesium may worsen muscle weakness

• Bowel obstruction or severe inflammatory bowel disease – the laxative effect could exacerbate symptoms

• Active gastrointestinal bleeding – may worsen fluid loss and electrolyte imbalance

Pregnant and breastfeeding women should seek medical advice before supplementing. Standard-dose magnesium supplements are generally considered safe during pregnancy if needed, but high-dose laxative or bowel preparation products containing magnesium citrate are typically avoided unless essential. Always follow the specific product guidance and your healthcare professional's advice.

Drug interactions are an important consideration. Magnesium citrate can significantly affect the absorption and efficacy of several medications including:

• Bisphosphonates (e.g., alendronic acid) – take bisphosphonates on an empty stomach and avoid minerals for the remainder of the restricted window

• Tetracycline antibiotics – take at least 2 hours before or 4-6 hours after magnesium

• Quinolone antibiotics – take at least 2 hours before or 4 hours after magnesium

• Levothyroxine – separate by at least 4 hours

• Neuromuscular blocking drugs (in hospital settings) – magnesium may enhance their effects

Older adults warrant special consideration due to age-related decline in kidney function and increased likelihood of multiple medications. Product information and the British National Formulary advise caution in this population, recommending lower starting doses and closer monitoring.

Anyone taking multiple medications or with complex medical conditions should discuss magnesium supplementation with their GP or pharmacist to ensure safety and appropriateness.

How to Minimise Side Effects When Taking Magnesium Citrate

Several practical strategies can help reduce the likelihood and severity of side effects when taking magnesium citrate supplements. Starting with a low dose and gradually increasing is perhaps the most effective approach. Begin with 100-200mg of elemental magnesium daily and increase slowly over 1-2 weeks, allowing your digestive system to adapt. This titration method significantly reduces gastrointestinal disturbance.

Timing and administration techniques include:

• Take with food – this slows absorption and reduces nausea and stomach upset

• Divide the daily dose – splitting your intake across 2-3 smaller doses throughout the day improves tolerance and absorption

• Ensure adequate hydration – drink plenty of water throughout the day

• Check product labels – look for the amount of elemental magnesium, not just the compound weight

Choosing the right formulation matters. Whilst magnesium citrate is well-absorbed, some people tolerate other forms better. Magnesium glycinate, for instance, tends to cause less diarrhoea whilst maintaining good bioavailability. Discuss alternatives with your pharmacist if side effects persist.

Dietary considerations can support supplementation. Consuming magnesium-rich foods (green leafy vegetables, nuts, seeds, whole grains, legumes) alongside moderate supplementation may reduce the need for high-dose supplements. Foods high in phytates (such as some whole grains and legumes) may potentially affect mineral absorption if consumed in large amounts at the same time as supplements.

Monitor your response by keeping a brief diary of symptoms, dose, and timing. This helps identify patterns and optimal dosing schedules. If diarrhoea persists, reduce the dose rather than discontinuing entirely, as your body may simply need a lower maintenance amount.

Regular review with healthcare professionals is advisable, particularly if you have underlying health conditions or take regular medications. Anyone taking supplements long-term should discuss this with their GP during routine appointments. The NHS advises not exceeding 400mg of magnesium daily from supplements unless advised by a clinician. Blood tests to check magnesium levels are rarely necessary for healthy individuals taking standard doses, but may be warranted if you have risk factors for deficiency or toxicity.

Remember that magnesium supplements are not suitable for everyone, and dietary sources should be optimised first. If you're considering supplementation for a specific health concern, consult your GP to ensure it's appropriate and to rule out underlying conditions requiring different treatment.

Frequently Asked Questions