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All you need to know about magnesium

Updated: Dec 23, 2022

Hi, I am doctor Leen. I am a general practitioner and a functional medicine doctor based in London. A big percentage of the population is not getting enough magnesium from their diet. Some of our daily habits including drinking alcohol, coffee, having high sugar diet and even stress can deplete our magnesium levels.

We know that magnesium deficiency can induce symptoms and increase susceptibility to stress. We also noticed that low levels of magnesium intake have been associated with depression. Despite the importance of magnesium, it remains one of the least understood and appreciated elements in human health and nutrition.

Let' s start with what is Magnesium?

Magnesium is used widely throughout the body. It supports energy production, blood pressure regulation, blood sugar metabolism, bone health, mood, digestive regularity, and much more. A magnesium deficiency may be a risk factor for osteoporosis, but it’s not clear to what extent low magnesium levels contribute to the risk of fractures in older age.

How can I replenish my magnesium?

Our approach is always diet first and reducing the things that we do that can deplete magnesium. It may be reasonable however, to add magnesium supplements in the early stages while you're trying to add magnesium rich food into your diet and implementing healthy habits such as reducing alcohol, sugar and practicing meditation.

Foods high in Magnesium?

1. Green vegetables

2. Milk & dairy foods

3. Nuts

4. Brown rice

5. Fish & meat

6. Bread (especially wholegrain)

7. Bananas and orange juice

How much magnesium do I need?

The amount of magnesium you need is:

  • 300mg a day for men (19 to 64 years)

  • 270mg a day for women (19 to 64 years) (1)

Signs of Magnesium deficiency?

  1. Muscle cramps/ twitching

  2. Muscle weakness and lethargy

  3. Insomnia

  4. Irritability

  5. Nausea/vomiting

  6. Contsiptation

  7. Migraines

  8. Menstrual cramps

  9. Confusion

Things we do that can make us lose magnesium?

  1. Alcohol

  2. Caffeine

  3. Stress

  4. Sugar

  5. Soda and other sugar-filled drinks

  6. Consuming a lot of processed food

  7. Some prescription medications (such as omeprazole or some blood pressure medications)

How to Test Magnesium Levels?

The most common way is a serum (blood) magnesium test. However, it is a poor indicator of the total magnesium content and availability in the body, because only 1% of magnesium is found in the extracellular fluid.(2)

A more accurate way to test magnesium status is to look at the amount of magnesium in your red blood cells. This way, we can evaluate the levels of magnesium in your cells.

A more complicated method of determining magnesium status relies on intravenous magnesium loading followed by a 24 h urine collection, to measure what percentage of administered dose is retained, from which an assessment of magnesium status can be derived. This retention test relies heavily on the reliability and standardization of the 24 h urine measurement, which is not uniformly accepted (3)

What supplements should I take?

We do not recommend starting a supplement without discussing with a healthcare professional first. You can book an appointment with us '' for a full consultation and blood test for personalised supplements. But here is what you need to know before buying a magnesium supplement.

Magnesium supplements are available in a variety of forms. Absorption of magnesium from different kinds of magnesium supplements varies. We know that magnesium oxide or magnesium carbonate are not absorbed well. We often prefer to use magnesium citrate, magnesium glycinate or magnesium threonate.

- Magnesium citrate is most helpful for people suffering from constipation. Remember, too much of magnesium citrate can give you diarrhoea.

- Magnesium glycinate form is more useful for conditions like anxiety, insomnia, chronic stress, and inflammatory conditions. Usually has the least side effects.

- Magnesium threonate is good for the 'brain' for conditions such as dementia.

Other fun ways to get magnesium in?

Magnesium epsom salt bath, maybe with some lavender drops. Wow! makes a great way to end your day.

What happens if I take too much magnesium?

Taking high doses of magnesium (more than 400mg) for a short time can cause diarrhoea.

There's not enough evidence to say what the effects might be of taking high doses of magnesium for a long time.

Who can't take magnesium supplements?

If you have kidney disease it's best to discuss with a healthcare professional first


2017;57(9):1115-1128. doi:1080/03630242.2016.1235074



(4) Fard FE, Mirghafourvand M, Mohammad-Alizadeh Charandabi S, Farshbaf-Khalili A, Javadzadeh Y, Asgharian H. Effects of zinc and magnesium supplements on postpartum depression and anxiety: a randomized controlled clinical trial. Women Health.

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