How much magnesium glycinate per day is appropriate depends on your individual needs, age, and health status. For UK adults, the Reference Nutrient Intake for total elemental magnesium is 300 mg daily for men and 270 mg for women. When supplementing with magnesium glycinate, typical doses range from 100–400 mg of elemental magnesium per day, though it's essential to check product labels carefully as magnesium glycinate contains only approximately 14% elemental magnesium by weight. This article explains recommended dosages, factors affecting your requirements, and how to supplement safely under UK guidance.

What Is Magnesium Glycinate and Why Is It Used?

Magnesium glycinate is a form of magnesium supplement in which magnesium is bound to the amino acid glycine. This formulation may be better absorbed than some other magnesium salts such as magnesium oxide, though evidence varies between studies. Magnesium glycinate is often reported to cause fewer digestive side effects than some other magnesium formulations.

Magnesium is an essential mineral involved in over 300 enzymatic reactions throughout the body. It plays critical roles in energy metabolism, protein synthesis, muscle and nerve function, blood glucose control, and blood pressure regulation. Adequate magnesium status is also necessary for bone health, as approximately 60% of the body's magnesium is stored in skeletal tissue. UK National Diet and Nutrition Survey data suggests that some population groups, particularly adolescents, may have magnesium intakes below recommended levels.

Common reasons people use magnesium glycinate include:

• Management of diagnosed magnesium deficiency

• Support for muscle function (though evidence for effectiveness in general muscle cramps is limited)

• Some people report improved sleep quality, though evidence specifically for magnesium glycinate is limited

• Some individuals use it for stress management, though evidence remains preliminary

• Support for overall health maintenance

Whilst magnesium glycinate is available as an over-the-counter supplement, it is important to recognise that supplementation should ideally complement, rather than replace, a balanced diet rich in magnesium-containing foods such as green leafy vegetables, nuts, seeds, whole grains, and legumes.

Recommended Daily Magnesium Glycinate Dosage in the UK

The UK's Department of Health and Social Care has established Reference Nutrient Intakes (RNIs) for total elemental magnesium, which vary according to age and sex. For adults aged 19 and over, the RNI is 300 mg per day for men and 270 mg per day for women. These figures represent the amount of elemental magnesium required to meet the needs of 97.5% of the population and should be considered when determining supplementation levels.

When taking magnesium glycinate supplements, it is essential to distinguish between the weight of the compound and the amount of elemental magnesium it contains. Magnesium glycinate typically contains approximately 14% elemental magnesium by weight, meaning a 500 mg tablet of magnesium glycinate may provide only about 70 mg of elemental magnesium. Always check the supplement label for the elemental magnesium content rather than the total compound weight.

Typical supplementation ranges for magnesium glycinate:

• General supplementation: 100–400 mg elemental magnesium daily

• For diagnosed deficiency: Your GP may recommend specific doses with appropriate monitoring

• Guidance level: The UK Expert Group on Vitamins and Minerals has set a guidance level for supplemental magnesium at 400 mg per day for adults (in addition to dietary intake)

It is generally advisable to start with a lower dose (100–200 mg elemental magnesium) and gradually increase as tolerated, particularly if you are new to magnesium supplementation. Dividing the daily dose into two or three smaller doses taken with meals can improve absorption and reduce the likelihood of gastrointestinal side effects. If you have been diagnosed with magnesium deficiency through blood tests, your GP or healthcare provider may recommend specific therapeutic doses, which should be taken as directed.

Factors That Affect Your Magnesium Glycinate Requirements

Individual magnesium requirements can vary based on numerous physiological, lifestyle, and medical factors. Understanding these variables is important for determining the appropriate supplementation level for your specific circumstances.

Age and sex influence baseline requirements, with men generally requiring slightly more magnesium than women due to greater muscle mass. During pregnancy, requirements remain at 270 mg daily (the same as for non-pregnant women), while during lactation, requirements increase modestly to 320 mg daily. Older adults may have increased needs due to reduced absorption efficiency and higher rates of medication use that can affect magnesium status.

Medical conditions can significantly impact magnesium requirements. Gastrointestinal disorders such as Crohn's disease, ulcerative colitis, coeliac disease, and chronic diarrhoea can impair magnesium absorption and increase losses. Type 2 diabetes is associated with increased urinary magnesium excretion, and poorly controlled diabetes may necessitate higher intake. Chronic kidney disease requires careful monitoring, as impaired renal function can lead to magnesium accumulation; supplementation should only occur under specialist supervision in this context.

Medications that can affect magnesium status include:

• Proton pump inhibitors (PPIs) such as omeprazole and lansoprazole

• Loop and thiazide diuretics (furosemide, bendroflumethiazide)

• Some antibiotics (aminoglycosides)

• Certain chemotherapy agents (particularly cisplatin)

Lifestyle factors also play a role. Regular intense physical activity increases magnesium losses through sweat. High alcohol consumption interferes with magnesium absorption and increases urinary excretion. There is some observational evidence suggesting associations between chronic stress and altered magnesium status. If you have any of these risk factors, discuss appropriate supplementation levels with your GP or a registered dietitian.

Signs You May Be Taking Too Much Magnesium Glycinate

Whilst magnesium glycinate is generally well tolerated compared to other magnesium formulations, excessive intake can lead to adverse effects. The body has mechanisms to regulate magnesium levels, primarily through renal excretion, but these can be overwhelmed by very high supplemental doses or compromised by kidney dysfunction.

The most common sign of excessive magnesium intake is diarrhoea, which can occur even at doses within the UK guidance level of 400 mg supplemental magnesium per day, though individual tolerance varies. This osmotic effect results from unabsorbed magnesium drawing water into the intestinal lumen. Other gastrointestinal symptoms may include nausea, abdominal cramping, and bloating. These effects are generally dose-dependent and resolve upon reducing or discontinuing supplementation.

Hypermagnesaemia (elevated blood magnesium levels) is uncommon in individuals with normal kidney function but can occur with excessive supplementation, particularly in those with renal impairment. Early signs include:

• Lethargy and generalised weakness

• Nausea and vomiting

• Facial flushing

• Low blood pressure (hypotension)

• Reduced reflexes

Severe hypermagnesaemia (serum magnesium >2.5 mmol/L) is a medical emergency and may present with:

• Significant muscle weakness

• Difficulty breathing due to respiratory muscle involvement

• Cardiac arrhythmias or heart block

• Confusion or altered consciousness

If you experience persistent diarrhoea, unusual muscle weakness, irregular heartbeat, or breathing difficulties whilst taking magnesium supplements, discontinue use immediately and seek urgent medical attention. For severe symptoms such as collapse, severe breathlessness, or chest pain, call 999 or go to A&E. Individuals with chronic kidney disease, heart block, or myasthenia gravis should not take magnesium supplements without specialist medical supervision.

If you suspect an adverse reaction to a magnesium supplement, you can report it through the MHRA Yellow Card scheme.

How to Take Magnesium Glycinate Safely and Effectively

Optimising the safety and efficacy of magnesium glycinate supplementation involves attention to timing, dosing strategy, and awareness of potential interactions with other medications and nutrients.

Timing and administration: Magnesium glycinate is best absorbed when taken with food, which also minimises the risk of gastrointestinal upset. Dividing your daily dose into two or three smaller doses (e.g., morning and evening, or with each main meal) can enhance absorption, as the intestinal transport mechanisms for magnesium have limited capacity. Many people prefer taking magnesium glycinate in the evening, though evidence for its effects on sleep quality is limited and individual responses vary.

Drug interactions require consideration. Magnesium can bind to certain medications in the gastrointestinal tract, reducing their absorption. Separate magnesium supplements from:

• Bisphosphonates (e.g., alendronate): Take on an empty stomach and wait at least 30 minutes before taking magnesium

• Tetracycline antibiotics: Take at least 2 hours before or 4-6 hours after magnesium

• Quinolone antibiotics (e.g., ciprofloxacin): Take at least 2 hours before or 4-6 hours after magnesium

• Levothyroxine: Separate by at least 4 hours

• Iron supplements: Take at different times of day

• Some HIV medications (e.g., dolutegravir): Check with your pharmacist for specific advice

Magnesium may enhance the effects of blood pressure medications and muscle relaxants; discuss concurrent use with your GP if you take these medications.

Quality and selection: Choose supplements from reputable manufacturers that adhere to Good Manufacturing Practice (GMP) standards. Look for products that clearly state the elemental magnesium content per dose. Third-party testing certifications can provide additional assurance of quality and purity.

Monitoring and medical guidance: Before starting supplementation, consider whether dietary optimisation might address your needs. If you have existing medical conditions, take regular medications, or are pregnant or breastfeeding, consult your GP or a registered dietitian before beginning magnesium supplementation. If you are supplementing to address diagnosed deficiency, arrange follow-up blood tests as recommended by your healthcare provider to assess response to treatment. Maintain open communication with your healthcare team about all supplements you take, as this information is relevant to your overall care and medication management.

Frequently Asked Questions