What is the relationship between magnesium deficiency and fatigue? Dietary tips and solutions for people who tire easily

Does a Magnesium Deficiency Lead to Fatigue? What We Know

Are you feeling tired on a weeknight even though you’ve slept well, and wondering if you might be lacking magnesium? This article explains what we do and do not know about how magnesium works and the relationship between its deficiency and fatigue.

What does magnesium do in the body?

According to documents from the Ministry of Health, Labour and Welfare, magnesium is a nutrient involved in building bones and teeth, supporting the function of many enzymes (substances that assist chemical reactions in the body), and creating energy.

Furthermore, the same Ministry of Health, Labour and Welfare documents state that it is involved in muscle contraction, nerve signal transmission, and the regulation of body temperature and blood pressure. Since it is a nutrient deeply involved in energy production, muscles, and nerves, it is natural to wonder about its connection to fatigue.

Reasons why we can—and cannot—say that a deficiency leads to fatigue

Because it is a nutrient involved in energy production for physical activity, it makes sense to think that a lack of it would be linked to fatigue. However, understanding how it works and confirming that a deficiency is the cause of your fatigue are two different things.

The NHS, a public health agency in the UK, lists causes of tiredness and fatigue such as lack of sleep, insomnia, lifestyle habits, stress, and depression. Even on days when you feel exhausted by the evening, it is entirely possible that the cause lies in your sleep or daily rhythms. We recommend not suspecting magnesium alone but considering other causes as well. The causes of persistent fatigue and guidelines for seeking medical attention will be organized in later sections.

Can magnesium relieve fatigue? The limits of what a single small study can tell us

In considering whether magnesium can relieve fatigue, there is one experiment that provides a clue. A 2022 study randomly divided 22 university-aged men and women into two groups, comparing a group that took 350 mg of magnesium daily for 10 days against a placebo group that took a pill with no active ingredients.

The results showed that in the group that supplemented with magnesium, muscle pain 24, 36, and 48 hours after exercise was about 1–2 levels lower on a 6-point scale compared to before supplementation. The placebo group showed no clear change.

However, what was examined was muscle pain, not the feeling of fatigue itself. The number of participants was small (22 people), and this is only the result of one study. Also, 350 mg was the amount used in the study and is not a suggested guideline for readers to try themselves.

In another 2011 study, 198 men aged 30–55 working full-time took a variety of vitamins and minerals. The group that took them rated their physical stamina higher at multiple points in time. This study did not look at the effects of magnesium alone.

These two results should be taken as small reports rather than a guarantee that supplementing with magnesium will relieve fatigue.

What are the symptoms of magnesium deficiency, and how do fatigue and sluggishness manifest?

Are evening sluggishness, lingering fatigue even after sleeping, and leg cramps signs of a magnesium deficiency? Here, we distinguish between symptoms listed in official documents and those that may be caused by other factors, and introduce ways to organize your own health issues.

Evening decline in concentration, sluggishness, and fatigue that remains after sleeping

You find your concentration dropping during an evening meeting and feel wiped out when you get home. When such days continue, you start to wonder if you are lacking nutrients.

The Ministry of Health, Labour and Welfare’s eJIM materials list malaise and lassitude as initial symptoms of magnesium deficiency. Malaise refers to a general feeling of sluggishness, and lassitude refers to a lack of physical strength. Evening sluggishness and fatigue that lingers after sleeping overlap somewhat with these symptoms.

However, you cannot definitively diagnose a magnesium deficiency based on this alone. A review summarizing studies on the elderly found that mild magnesium deficiency is generally asymptomatic, and it is difficult to distinguish symptoms like malaise from those caused by aging.

For those researching components specifically for concentration, please also refer to Is there scientific evidence for the benefits of Lion's Mane? Organizing the current state of research, which we have introduced previously.

Leg cramps, headaches, and feeling restless

Your calves cramp, you get headaches, and you feel restless and unsettled. These symptoms are sometimes spoken of in connection with magnesium.

However, the only things we can provide evidence for in this article are malaise and lassitude. We have not cited any documents that can pinpoint leg cramps, headaches, or restlessness as being caused by magnesium deficiency. All of these symptoms can be caused by other factors.

We also cannot say that taking magnesium will alleviate headaches or cramps. If your symptoms are severe or keep recurring, consult a medical institution before attempting to manage them with supplements.

Try taking notes on your health condition for a few days

While there is no way to verify a magnesium deficiency yourself, keeping a record for a few days is helpful. Take 1–2 minutes before bed to write notes on your smartphone.

Items to include: dietary content (e.g., did you eat breakfast, or was it just noodles?), hours of sleep, intensity of fatigue, and the presence of leg cramps or headaches. For fatigue intensity, it is easier to keep track if you use a 3-level scale—"None, Slight, Strong"—for both morning and evening.

Once you have 3–5 days of data, you may find common patterns, such as days with strong fatigue coinciding with short sleep or imbalanced meals. This log cannot diagnose a deficiency. Its purpose is to show the progress of your symptoms when you visit a doctor.

When fatigue persists: Other causes besides magnesium and when to see a doctor

When fatigue continues, it is tempting to suspect a magnesium deficiency. However, there are other causes of fatigue, such as sleep issues or underlying medical conditions. Based on official documents, we will organize symptoms that warrant consulting a medical institution and where to go if you experience persistent psychological distress.

There is more than one cause of fatigue: Sleep, anemia, lifestyle rhythms, etc.

On weekdays you go to sleep around midnight, and on holidays you can't get up until near noon. After such a lifestyle continues, if your body feels heavy, you might suspect a lack of nutrients. However, as mentioned above, the causes of fatigue include sleep deprivation, insomnia, lifestyle habits, and stress; nutrition is only one factor.

The NHS materials list sleep apnea, iron-deficiency anemia, diabetes, hyperthyroidism, and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) as examples of diseases that can cause fatigue. This is not a checklist to determine if these apply to you, but examples to help you understand that illnesses can sometimes hide behind fatigue.

In the aforementioned log, try adding your bedtime and wake-up time, as well as how busy you were at work. Clues other than nutrition will likely emerge.

Symptoms for which you should see a doctor early

NHS materials advise consulting your primary care physician if unexplained fatigue lasts for several weeks, if it is affecting your daily life, or if it is accompanied by weight loss or changes in mood. If this applies to you, consult a professional before trying to manage it with supplements.

The same material advises seeking medical attention promptly if fatigue is accompanied by chest pain, severe shortness of breath, fainting, confusion, or sudden weakness. In these cases, it is important to consult a doctor before continuing to keep a log for several days.

The same material also lists persistent severe fatigue lasting at least 3 months and significant difficulty with daily activities as examples of symptoms for ME/CFS. You cannot decide if this applies to you based solely on the content of this article. If severe fatigue continues for a long time and hinders your daily life, we recommend consulting a doctor rather than self-diagnosing.

Where to go for help when psychological distress persists

You may feel depressed for no reason or restless due to intense anxiety. If such a state continues, some may wonder if they are lacking nutrients. However, psychological distress can also occur due to causes other than nutritional deficiency, such as stress or depression.

The Ministry of Health, Labour and Welfare’s "Kokoro no Mimi" (Ear of the Heart) recommends visiting a medical institution if you are unable to sleep well for more than two weeks or if it interferes with your work. The two-week threshold is a trigger to consider seeking a medical consultation when sleepless nights continue.

If you have feelings of depression or intense anxiety, consult a specialist, such as your primary care physician or a psychosomatic clinic, before reviewing your diet. Having a log of your symptoms and daily life will make it easier to communicate your situation.

If you are considering a magnesium test: How to view reference values and talk to your doctor

Whether you have enough magnesium cannot be determined by symptoms alone. Based on official documents, we will organize whether there are reference values for determining fatigue and what you should convey when discussing a test with a medical institution.

To avoid diagnosing a deficiency based on symptoms alone

My calves cramp easily in the evening, and my body feels heavy in the morning. When such days continue, you start to suspect a magnesium deficiency. However, as noted, fatigue, leg cramps, and headaches can also be caused by other factors like sleep or illness.

Even if you check many boxes on an online checklist, it does not provide proof that you are deficient in magnesium. We recommend consulting a medical institution about the symptoms you are concerned about before deciding that you "must be deficient" and buying supplements.

Are there reference values for determining fatigue?

The Ministry of Health, Labour and Welfare documents do not list reference values for magnesium intake or blood concentration levels to diagnose fatigue.

Recommended daily intake for adults indicates how much you should eat on a daily basis. This is different from a cutoff point for determining the presence or absence of fatigue.

By the way, regarding food ingredients other than magnesium often mentioned in discussions of fatigue and concentration, we have introduced how much is known through research in What are the effects of Lion's Mane? The current state of research, how to eat it, and points of caution, so please refer to that as well.

How to talk to your doctor when you want to take a test

Before your visit, have your most recent health checkup results and a few days of symptom notes ready. If you record the time you felt fatigue, sleep duration, dietary content, and the presence of leg cramps or headaches in your notes, the doctor will understand the progress of your symptoms.

Be sure to also inform the doctor of any medications or supplements you are taking.

Instead of specifying a test by saying, "Please give me a magnesium test," it is recommended to say, "I have been experiencing persistent fatigue, and I am worried that I might not be getting enough magnesium." The doctor will then determine what tests are necessary after looking at the symptoms as a whole.

How much magnesium do you need in a day? A list of foods high in magnesium

What are the recommended daily intake levels for adult men and women? We will organize the classification of foods high in magnesium, the units to look for on food labels, and how people who exercise or do strength training should think about intake.

What are the recommended levels for adults?

The recommended magnesium intake for adults listed in Ministry of Health, Labour and Welfare documents is 330–380 mg/day for men and 280–290 mg/day for women.

Do not try to meet this through dinner alone; it is better to consider the total daily intake, including breakfast, lunch, and snacks. We recommend using these figures as a starting point when reviewing your diet.

A list of foods high in magnesium

It is easier to find foods rich in magnesium if you categorize them into the following four groups:

• Legumes (soybeans, natto, etc.)
• Seaweed (wakame, hijiki, etc.)
• Nuts (almonds, etc.)
• Fish

Since content varies by food, we recommend checking the Ministry of Education, Culture, Sports, Science and Technology's Food Composition Database. These composition values are shown per 100g of edible portion.

100g is not necessarily the amount you eat at one time. For foods like dried seaweed or nuts where you eat small amounts at once, the amount of magnesium you actually ingest will be much lower than the table figures.

How people who do strength training or exercise should think about intake

When you continue strength training, you tend to think you need to take more than people who do not exercise. However, the recommended intake used as a basis for this article is for adults, and no separate value can be provided for those who exercise.

Even those who exercise should start by reviewing their daily diet using the recommended adult intake as a guideline. You can reasonably increase your intake by combining beans, seaweed, and nuts with meals that include a staple food, main dish, and side dishes.

On the other hand, Consumer Affairs Agency materials indicate that consuming large amounts of magnesium can cause loose stools (diarrhea). Just because you exercise a lot does not mean you should simply increase your intake.

Skipping breakfast, noodles, and coffee: How to adjust your eating habits

You will learn what to add and how when you skip breakfast, have days where lunch is just noodles, or get by on coffee. We will organize how to reasonably incorporate legumes, seaweed, nuts, and fish into your daily diet by habit.

For those who tend to skip breakfast, start with one dish until lunch

If you keep skipping breakfast, you won't be able to stick to it if you try to fix the entire meal at once. The Ministry of Health, Labour and Welfare’s Dietary Guidelines recommend starting the day with breakfast. An example of a breakfast shown by the Ministry of Agriculture, Forestry and Fisheries includes 1.5 portions of staple food, 1 side dish, 1 main dish, 1 milk/dairy product, and 1 fruit. You don't need to prepare all of this; start by deciding on one item to eat by lunch. For mornings when you don't have time to prepare at home, we recommend a pre-packaged protein bar made with nuts or soybeans. You can tell if it contains nuts or soybeans by checking the ingredient label.

How to add to meals on days when lunch tends to be noodles or convenience store food

On days when you eat udon, ramen, or pasta for lunch, meals tend to be centered on staple foods. The Ministry of Agriculture, Forestry and Fisheries’ lunch example consists of 2 portions of staple food, 2 side dishes, 2 main dishes, 2 milk/dairy products, and 1 fruit. On noodle days, try adding a side dish and a main dish. You can easily incorporate legumes, seaweed, and fish through a seaweed salad, tofu, or a deli dish containing fish.

For those who drink multiple cups of coffee, rethink your diet

If you drink multiple cups of coffee while working, try increasing the days you incorporate legumes, seaweed, nuts, and fish into your diet before you try changing how much you drink. This article does not cite any documents showing a relationship between coffee intake and magnesium. Decide whether to reduce coffee after you have adjusted your diet. It is recommended to add the number of cups of coffee you drank to the aforementioned health log. Comparing it with your sleep and fatigue records will reveal trends in your own lifestyle.

Applying this to a daily menu

In the Ministry of Agriculture, Forestry and Fisheries’ meal examples, breakfast is composed of 1.5 portions of staple food, 1 side dish, 1 main dish, 1 milk/dairy product, and 1 fruit. Lunch is 2 portions of staple food, 2 side dishes, 2 main dishes, 2 milk/dairy products, and 1 fruit.

Those who tend to skip breakfast should try to think of a meal that includes a side dish using legumes or seaweed and a main dish of fish, referring to the breakfast example. For lunch, which often tends to be just noodles, adding one side dish and one main dish will bring it closer to the lunch example.

For those who tend to use snacks for mid-day fuel, replacing them with nuts is one option.

Comparing BRAIN PRO and store-bought protein bars for snacks on days with imbalanced meals

On afternoons when lunch consisted only of noodles, you might struggle with what to choose for a snack. You will learn how to read ingredient labels and how to compare the nutritional components of BRAIN PRO with store-bought protein bars using the same criteria.

Ingredients and nutrition labels to look at when choosing a snack

When choosing a protein bar for a snack, you can tell the difference by looking at two places on the back of the package. One is the ingredient label. You can verify here whether sugar, such as white sugar, or sweeteners are included. Also, check the ingredient label for allergens such as soybeans or nuts.

The other is the nutrition facts label. If you are eating it in the afternoon on a day when lunch was just noodles, paying attention to calories and salt equivalents will help you consider your total intake before dinner.

The contents of protein bars vary by product. It is recommended to compare values per bar.

Comparison table for BRAIN PRO and store-bought protein bars

BRAIN PRO contains 190 kcal, 11.1g of protein, 13.5g of fat, and 7.1g of carbohydrates per 35g bar. Of the carbohydrates, 4.9g is sugar and 2.2g is dietary fiber; the salt equivalent is 0.4g. The table below allows you to compare it with store-bought protein bars using the same criteria.

Product	Content	Sugar	Artificial Sweeteners	White Sugar	Protein (Source)
Calorie Mate Chocolate	80g (4 bars)	39.7g	None	Used	8.7g / Soy, Wheat
Myprotein Layered Protein Bar Birthday Cake	60g	21g	Used (Sucralose)	Used	20g / Milk, Soy
in Bar Protein Crunchy Choco	43g	11.7g	None	Used	17.9g / Soy, Milk
SOYJOY Almond & Chocolate	30g	7.6g	None	Used	5g / Soy
BRAIN PRO	35g	4.9g	None	None	11.1g / Plant-based (Pea)

Figures for each product are based on nutritional information published on each manufacturer's official website as of September 25, 2026. Changes may occur due to product revisions.

For those who wish to avoid white sugar, BRAIN PRO is recommended.

However, since it contains soybeans and almonds as ingredients, those with allergies to these should be cautious.

Are magnesium supplements necessary? How to choose and precautions regarding excess

When fatigue persists, some may think about supplementing with convenient pills. We will organize the order of prioritizing dietary adjustments, the upper limit when taking from sources other than regular food, symptoms of overconsumption, and who should consult a professional before using them.

The order of adjusting your diet before considering supplements

If you skipped breakfast and had only noodles for lunch, you might wonder in the evening if you should "add a supplement." In such cases, before grabbing a supplement, we recommend checking if legumes, seaweed, nuts, and fish are in your daily diet. As mentioned, the recommended intake is a figure for the total daily diet. First, adjust your diet.

If you still feel you are lacking nutrients even after adjusting your diet, then adding supplements is the way to go. When choosing supplements, read the label on the package. The Consumer Affairs Agency materials state that it should be indicated for magnesium nutritional functional foods that taking large amounts does not cure diseases or promote better health. It is important to confirm the recommended daily intake and warnings, and to remember that more is not necessarily better.

Symptoms likely to occur when taking too much

If you continue taking supplements, it becomes easy for the amount to increase due to their convenience. Ministry of Health, Labour and Welfare documents state that the tolerable upper intake level of magnesium from sources other than regular food for adults is 350mg/day. The tolerable upper limit is the daily maximum figure to avoid overconsumption.

In the same documents, there is no upper limit set for intake from regular foods. The amount to track is what you take from sources other than food, such as supplements. If you use two types of supplements, be sure to add their amounts together to verify.

As mentioned, one symptom that occurs when taking too much is loose stools (diarrhea). If your stomach becomes loose, review the amount you are using. If it continues, consult your doctor or pharmacist.

Those who should consult a doctor or pharmacist before using

Those who are visiting a hospital for treatment or taking medication should consult a doctor or pharmacist before starting supplements. It is important for those under treatment to follow their doctor's instructions. Pregnant or breastfeeding women should also consult a professional before use.

Also, if fatigue is prolonged or affects your daily life, the cause may lie elsewhere than magnesium. We recommend consulting your primary care physician before trying to manage it with supplements. When consulting, it will be easier to communicate if you bring the names and amounts of the supplements or medications you are using, as well as the notes you recorded on your symptoms.

Summary

Magnesium is a nutrient involved in energy production, as well as muscle and nerve function. While malaise and lassitude can appear in cases of magnesium deficiency, the cause of your fatigue is not necessarily a lack of magnesium. Furthermore, the referenced materials do not indicate a magnesium reference value for determining the presence or absence of fatigue.

There are other causes of fatigue, such as sleep, daily rhythms, and illness. If fatigue persists for weeks or interferes with your life, consult a medical institution before trying supplements.

We recommend starting by keeping a note of your health condition for a few days while incorporating legumes, seaweed, nuts, and fish into your breakfast, lunch, or as snacks. If you use supplements, do so only after confirming the upper intake limits and checking the labels.