Signs of magnesium deficiency. Symptoms, causes, and what to do
Magnesium deficiency is one of the most commonly overlooked nutritional problems in the UK.
Unlike iron or vitamin D, where awareness has grown and testing is more routine, magnesium rarely gets the same attention, despite being involved in over 300 biochemical processes in the body and being consistently low in many people's diets.
The symptoms of low magnesium are non-specific. Muscle cramps, poor sleep, fatigue, anxiety, and headaches are the kind of complaints that get attributed to stress, overwork, or just getting older. Not to a mineral that most people never think about. This is why low magnesium often goes unaddressed for a longtime.
This article covers what magnesium does, why low intake is so widespread, what thesigns of deficiency actually feel like, the best dietary sources, what supplementation looks like, and why some people consistently struggle with magnesium status even when their diet is broadly good.
"Magnesium is involved in more processes in the body than almost any other mineral — yet it is one of the most consistently under-consumed nutrients in the UK diet."
What magnesium actually does
Magnesium is a mineral that functions as a cofactor, meaning it is required for enzymes to work properly. It is involved in energy production, protein synthesis, muscle and nerve function, blood glucose regulation, and blood pressure control. It is also essential for DNA repair and synthesis.
For day-to-day wellbeing, the most practically relevant roles are:
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Muscles
Muscle function
Magnesium regulates the contraction and relaxation of muscle fibres. When magnesium is low, muscles are more prone to cramping, twitching, and tension. This is why muscle cramps are one of the most commonly reported signs of low magnesium.
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Sleep
Sleep quality
Magnesium activates the parasympathetic nervous system, the system responsible for rest and recovery, and regulates melatonin, the hormone that governs sleep-wake cycles. Low magnesium is consistently associated with difficulty falling asleep, lighter sleep, and more frequent waking.
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Stress
Stress and anxiety response
Magnesium plays a role in regulating the HPA axis, the system that controls the body's stress response, and in the function of GABA receptors, which have a calming effect on the nervous system. Low magnesium is associated with heightened anxiety and a reduced ability to manage stress.
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Energy
Energy production
ATP, the molecule that cells use for energy, must be bound to magnesium to be biologically active. Without adequate magnesium, cellular energy production is less efficient, contributing to fatigue.
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Bones
Bone health
Around 60 percent of the body's magnesium is stored in bones, and magnesium works alongside calcium and vitamin D in maintaining bone density. Chronically low magnesium contributes to bone loss over time.
Magnesium and vitamin D work together
Low magnesium can limit the effectiveness of vitamin D. Magnesium is required to activate the enzymes that convert vitamin D into its usable form — which means supplementing vitamin D without adequate magnesium may be less effective than expected.
Why magnesium deficiency is so common
The primary reason is dietary. Magnesium is found in whole grains, legumes, nuts, seeds, leafy green vegetables, and dark chocolate. Modern diets, which are heavy in processed and refined foods, tend to be low in these sources. Refining grains removes the germ and bran where most of the magnesium is concentrated, which iswhy white bread and white rice provide far less magnesium than their wholegrain equivalents.
Several other factors compound the problem. Magnesium is depleted by both physical and psychological stress, because the body uses more magnesium when the stress response is active. High caffeine and alcohol intake both increase magnesium excretion through the kidneys. Certain medications, including proton pumpinhibitors (PPIs), diuretics, and some antibiotics, reduce magnesium absorptionor increase its excretion.
Soil depletion is also a relevant factor. Intensive farming practices have reduced the magnesium content of soil over decades, meaning that even foods that were historically reliable magnesium sources now contain less than they once did.
It is also worth noting that standard blood tests are a poor measure of magnesium status. Only around 1% of the body's magnesium is in the bloodstream. The rest is stored in bones and soft tissue. A serum magnesium test can appear normal even when intracellular magnesium is low, which means deficiency can go undetected through routine testing.
Symptoms of magnesium deficiency. What low levels actually feel like
Because magnesium is involved in so many systems, the symptoms of low magnesium arewide-ranging. The most consistently reported ones are:
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Most common
Muscle cramps and twitches
Cramps in the legs, feet, and calves, particularly at night, are strongly linked to low magnesium. Eye twitches and muscle spasms elsewhere in the body are also common.
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Sleep
Poor sleep and restlessness
Difficulty falling asleep, waking during the night, or consistently unrefreshing sleep despite adequate hours in bed. Low magnesium is associated with reduced sleep quality and lighter sleep architecture.
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Energy
Fatigue and low energy
Persistent tiredness that does not resolve with rest. Because magnesium is required for ATP production, low magnesium directly reduces cellular energy availability.
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Stress
Anxiety and heightened stress response
A lower threshold for feeling stressed or anxious, difficulty winding down, and a sense of being on edge. The connection between magnesium and the nervous system's calming pathways makes this one of the more well-documented symptoms.
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Head
Headaches and migraines
Low magnesium is associated with increased frequency of headaches and is particularly well-established as a contributing factor in migraines. Magnesium affects neurotransmitter release and blood vessel constriction in ways that are relevant to migraine pathways.
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Heart
Heart palpitations
Magnesium plays a role in regulating heart rhythm. Low levels can contribute to irregular or noticeable heartbeats. If you are experiencing frequent palpitations, speak with your GP. While magnesium can be a factor, palpitations have several potential causes that warrant investigation.
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Digestive
Constipation
Magnesium helps regulate muscle contractions in the digestive tract. Low magnesium can slow gut motility and contribute to constipation.
When to speak to your GP
If you are experiencing persistent muscle cramps, poor sleep, fatigue, or frequent headaches — particularly if several of these symptoms are present together — it is worth raising with your GP. While a serum magnesium test has limitations, it is a reasonable starting point. If you are on medications that affect magnesium absorption or excretion, discussing magnesium status with your GP is particularly worthwhile.
The best food sources of magnesium
Getting magnesium from food is always the first priority. The richest dietary sources are:
Seeds. The richest natural sources
Pumpkinseeds, chia seeds, and hemp seeds are among the most concentrated sources of magnesium available. A small handful of pumpkin seeds provides a meaningful contribution toward daily needs. Seeds are also easy to add to existing meals. On porridge, in salads, or blended into smoothies.
Approximate magnesium per 100g serving
Pumpkin seeds550mg
Hemp seeds700mg
Almonds270mg
Chia seeds335mg
Dark chocolate (70%+)228mg
Spinach (cooked)87mg
Black beans70mg
Brown rice (cooked)44mg
UK recommended daily intake: 300mg (men) | 270mg (women)
Dark leafy greens
Spinach, kale, and Swiss chard are good sources, particularly when cooked. Cooking concentrates the magnesium content by reducing water volume. Leafy greens are also good sources of other nutrients that work alongside magnesium, including calcium and vitamin K.
Legumes
Black beans, edamame, kidney beans, and lentils all provide meaningful amounts of magnesium. Legumes are also high in fibre, which supports the gut environment where many nutrients are absorbed.
Nuts
Almonds, cashews, and Brazil nuts are among the better nut sources of magnesium. A small portion as a snack or added to meals contributes to daily intake without requiring significant dietary changes.
Wholegrains
Brown rice, oats, quinoa, and wholemeal bread provide more magnesium than their refined equivalents. Switching from white to wholegrain versions of staple foods is one of the more straight forward ways to increase magnesium intake.
Dark chocolate
70% cocoa or above provides a meaningful amount of magnesium per serving. Worth noting rather than treating as a primary strategy. But a genuine source.
The limitations of diet alone
Even a diet that includes regular nuts, seeds, and leafy greens may not consistently meet magnesium needs. This is particularly true during periods of high stress, when the body's magnesium requirements increase and excretion rises.
Supplementation. What to know
Magnesium is available as a supplement in several different forms, and the form matters. The most common forms are:
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Best absorbed
Magnesium glycinate
Generally considered the best-absorbed form and the most appropriate for addressing deficiency and supporting sleep and anxiety. It is less likely to cause digestive side effects than other forms.
Recommended
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Good alternative
Magnesium citrate
Well absorbed and commonly available. It has a mild laxative effect at higher doses, which can be useful if constipation is a symptom but is worth being aware of.
Well absorbed
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Least effective
Magnesium oxide
The most common form in budget supplements. It has poor bioavailability, meaning the body absorbs relatively little of the magnesium it contains. Generally not the most useful form for addressing deficiency.
Poor bioavailability
For most people looking to address low magnesium, magnesium glycinate or citrate in the range of 200 to 400mg daily is a reasonable starting point. Magnesium is water-soluble, which means excess is generally excreted rather than accumulated, but very high doses can cause digestive upset. Taking it in the evening is a common approach given its association with sleep quality.
Why some people struggle more than others. The genetics dimension
For most people, low magnesium comes down to diet and lifestyle factors. But some people find that their magnesium status remains lower than expected even when their diet includes good sources and they are supplementing consistently.
Genetic variants influence how efficiently the body absorbs and retains magnesium. The TRPM6 and TRPM7 genes encode magnesium transport channels in the intestine and kidney. Variants in these genes affect how efficiently magnesium is absorbed from food and how much is retained by the kidneys rather than excreted. Variants in other transporter genes similarly influence magnesium handling at the cellular level.
These genetic differences help explain why magnesium needs are genuinely personal. Two people eating the same diet can have meaningfully different magnesium status. Not because of willpower or effort, but because their bodies handle themineral differently at a biological level.
In the Boone app
Boone analyses genetic variants relevant to magnesium absorption and transport — showing you whether your body is likely to handle magnesium efficiently or whether you may need to be more deliberate about your intake from food and supplementation. Combined with the food log tracking your dietary magnesium sources and the micro nutrition scores showing what your magnesium picture means for your Sleep, Energy, and overall nutritional status, it gives you a personal picture rather than a generic one.
What to do if you think your magnesium is low
Start with diet. Increasing your intake of pumpkin seeds, leafy greens, legumes, nuts, and wholegrains is the most sustainable foundation. These foods provide magnesium alongside a range of other nutrients that support overall health.
If dietary changes are not sufficient, or if you are in a period of high stress, using medications that affect magnesium, or experiencing several of the symptoms described above, magnesium glycinate or citrate supplementation at 200 to 400mg daily is a well-tolerated and evidence-supported option.
If symptoms are significant or persistent, speak with your GP. While routine blood tests have limitations for detecting magnesium deficiency, they are a useful starting point and help rule out other contributing factors.
For people who find that their magnesium status remains inconsistent despite good dietary habits and supplementation, understanding the genetic factors that influence how your body absorbs and retains magnesium provides the next layer of personal context.
"Magnesium needs are genuinely personal. Two people eating the same diet can have meaningfully different magnesium status. Their bodies handle the mineral differently at a biological level."
The most common signs are muscle cramps, particularly at night, poor sleep, persistent fatigue, anxiety, and headaches. Standard blood tests measure serum magnesium, which only reflects around one percent of total body magnesium and can appear normal even when levels are functionally low. If you are experiencing several of these symptoms, raising it with your GP is a sensible step.
Magnesium glycinate is generally considered the most bioavailable and best-tolerated form, particularly for sleep and anxiety. Magnesium citrate is also well absorbed and widely available. Magnesium oxide, the most common form in budget supplements, has poor bioavailability and is the least useful for addressing deficiency.
Yes. Magnesium plays a direct role in activating the parasympathetic nervous system and regulating melatonin production. Low magnesium is consistently associated with difficulty falling asleep, lighter sleep, and more frequent waking. This is one of the reasons magnesium supplementation taken in the evening is commonly reported to improve sleep quality.
Yes. Physical and psychological stress both increase the body's magnesium requirements and raise urinary magnesium excretion. This creates a cycle where stress depletes magnesium, and low magnesium makes the stress response harder to regulate. High caffeine and alcohol intake also increase magnesium excretion through the kidneys.
The richest sources are pumpkin seeds, hemp seeds, chia seeds, almonds, cashews, dark chocolate (70 percent cocoa or above), spinach, black beans, and wholegrains including oats and brown rice.
Yes. Variants in genes including TRPM6 and TRPM7, which encode magnesium transport channels in the intestine and kidney, influence how efficiently the body absorbs magnesium from food and how much is retained rather than excreted. These differences mean that magnesium needs vary between individuals even when diet is similar.
Understand your personal magnesium picture.
Boone analyses your genetic profile for magnesium absorption and transport variants and connects those insights to your real diet. It shows you your dietary magnesium sources, your micro nutrition scores across Sleep, Energy, and Immunity, and personalised food recommendations that address your specific gaps.
Download the Boone app and discover what your nutritional picture looks like.
