Magnesium: What It Actually Does, Which Type Is Best and How to Take It

There isn't one magnesium that's best for everyone, and not everyone needs to take a magnesium supplement. The form, dose, reason for taking it and how well you tolerate it all matter. Here’s are the key points I think everyone should know about before starting a magnesium supplement:  

Magnesium contributes to normal muscle and nerve function, energy production and protein synthesis, as well as processes involved in blood glucose and blood pressure regulation.  

This is why magnesium is often discussed in relation to muscle function, tiredness and general wellbeing. 

But there's an important distinction between magnesium being essential for these processes and taking extra magnesium necessarily improving them if you're already getting enough. 

More isn't automatically better. 

Good food sources include nuts and seeds, beans and other legumes, wholegrains, dark leafy green vegetables, avocado, tofu and dark chocolate. Starting with a varied diet is a good way to support your magnesium intake before considering a supplement.  

Different magnesium supplements contain magnesium combined with different compounds, which can affect absorption and how they behave in the digestive system. 

Two forms you'll commonly come across are magnesium glycinate/bisglycinate and magnesium citrate. 

Magnesium glycinate/bisglycinate is magnesium combined with the amino acid glycine. It's a popular choice because it is generally well tolerated and doesn't tend to have the same laxative effect as some other forms. 

Magnesium citrate is magnesium combined with citric acid. It is also relatively well absorbed and can have a laxative effect, which may be useful if constipation is an issue.  

So rather than asking “Which is the best magnesium?”, I'd ask “Which is the best magnesium for me?” 

If you're looking for general supplementation and want something that's usually gentle on the stomach, magnesium glycinate/bisglycinate is a form I often recommend considering. 

If constipation is also an issue, magnesium citrate may make more sense. 

Magnesium glycinate is particularly popular for sleep, but I think it's important to keep expectations realistic. 

Research into magnesium and sleep is still developing, so I wouldn't describe it as a guaranteed sleep solution. If sleep is your main reason for trying magnesium, glycinate or bisglycinate is a reasonable form to consider, alongside looking at the wider factors that affect sleep. 

How much magnesium you need depends on your age and sex, with requirements increasing during pregnancy.  

These recommendations include magnesium from food, drinks and supplements.  

You may be surprised by how much magnesium some everyday foods provide: 

Amounts are approximate and can vary depending on the food and preparation. Source: National Institutes of Health, Office of Dietary Supplements. 
 
You can see here why I don't think everyone needs a magnesium supplement. A varied diet can provide a good amount of magnesium.  

One thing that can be confusing when comparing magnesium supplements is the number on the front of the pack. 

You might see a product described as containing 1,000 mg, 2,000 mg or even 4,000 mg of magnesium, but that doesn't necessarily mean you're taking that much actual elemental magnesium. 

That's because the magnesium is combined with another compound, such as citrate or glycinate. The important number to look for is the amount of elemental magnesium. 

For example, a product may contain a large amount of a magnesium compound but provide a much smaller amount of elemental magnesium. 

The supplement label should declare the amount of elemental magnesium, rather than simply the weight of the whole magnesium-containing compound.  

This is one of the first things I check when comparing magnesium products. 

There isn't one universally correct time of day to take a magnesium supplement. 

For general supplementation, consistency matters more than choosing a particular hour. I usually suggest taking it at a time that fits naturally into your routine and that you tolerate well. 

If you're trying magnesium glycinate because you're hoping it may support sleep, taking it in the evening is a reasonable approach, which is what I do. 

If you're taking magnesium citrate for its laxative effect, choose a time when that effect is convenient for you. 

And if magnesium upsets your stomach, taking it with food may help. 

A personal note from Lauren 

I'm currently taking Revive Active Magnesium Complex because I'm training for a half marathon and sometimes experience restless legs in the evening. I like having magnesium as part of my routine during training, particularly because magnesium contributes to normal muscle and nervous system function. 

I wouldn't suggest magnesium as a treatment for restless legs, but it's an example of how I think about supplements personally: what am I taking, why am I taking it, and is the dose appropriate? 

For many people, magnesium can be taken regularly, but whether you need a daily supplement depends on your diet, your reason for taking it, the dose and your individual circumstances. 

For adults, the US National Institutes of Health sets an upper limit of 350 mg per day from magnesium supplements and medications. This does not include magnesium naturally present in food.  

That 350 mg figure isn't a target, it's an upper limit for supplemental magnesium.