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Vitamin D and Magnesium - Benefits, Dosages, and Why They Should Go Together

Medically reviewed by

E. P. Diamandis, MD, Ph.D


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Key takeaways

Vitamin D is quickly overtaking Vitamin C as the buzziest supplement on the market. Since patients with ailments from breast cancer to COVID-19 display decreased levels of Vitamin D, renewed interest has focused on this  vitamin, which is actually a hormone, that your body produces naturally when your skin is exposed to UV rays from the sun or other sources.. 

Moreover, any conversation about Vitamin D is incomplete without a discussion of the mineral magnesium.

Lets dig deep into this subject—what is Vitamin D, and what is magnesium for, for that matter? Why are they inextricably linked according to the science of nutrition? What do they do for the body, and what happens to the body when there isn’t enough of it? Should you supplement your diet with one? Both? And how much? Should you take a vitamin D test at home? This is everything you need to know about Vitamin D and magnesium,

What is Vitamin D3 and what does it do for your body?

Vitamin D3 is a form of Vitamin D, a fat-soluble hormone. Similar to but different from the form of Vitamin D that the skin produces when exposed to sunlight, Vitamin D3 can be obtained by eating certain animal products, including egg yolks, liver, fatty fish, fish oil, cheese, yogurt, and other foods. 

Few plant-based foods contain Vitamin D3. People unable to obtain sufficient Vitamin D from sun exposure should consider taking a Vitamin D3 supplement, especially if they are vegetarians, vegans, or otherwise avoid eating animal products.

Also known as “calciferol,” Vitamin D plays a crucial role in human health. Every cell has Vitamin D receptors. When Vitamin D3 or another calciferol binds to a Vitamin D receptor, it turns as many as 2,000 genes within the cell on or off, causing cellular changes.


Positive effects of Vitamin D

Studies have shown the ability of Vitamin D to switch off cancer-causing genes, switch on genes critical to immune system function, and have a positive impact on a variety of bodily systems. Examples of the positive effects of Vitamin D include:

  1. Better Bone Health - Vitamin D plays a key role in the absorption of calcium, which makes it critical for maintaining bone density, promoting bone crystallization, and preventing bone disorders like osteoporosis.
  2. Greater Insulin Control - Vitamin D3 has been shown to stimulate the pancreas, triggering its insulin-production functions.
  3. Lower Blood Pressure - Vitamin D3 reduces the concentration of the enzyme renin in the kidneys, which impacts blood vessels and blood pressure. A Boston University study demonstrated an improvement in blood pressure among hypertensive subjects when administered Vitamin D3.
  4. Better Heart Health - Two studies have correlated low Vitamin D levels with susceptibility to heart attacks. The reasons for this effect are not entirely clear, but doctors suspect that Vitamin D regulates heart cells, preventing the ventricle walls from getting too thick. Vitamin D may also improve cardiovascular endurance.
  5. More Stable Mood - Some studies have correlated healthy Vitamin D levels with reduced rates of clinical depression, especially seasonal affective disorder. This may be correlated to the fact that most people experience less exposure of the skin to sunlight, reducing their Vitamin D levels in the winter.
  6. Lower Susceptibility to Cancer - Some studies have linked Vitamin D to slowed rates of tumor growth. A study of 166 breast cancer patients revealed a 70% incidence of low Vitamin D levels, prompting scientists to hypothesize a link. Vitamin D paired with fiber has been linked to reduced formation of colon polyps, which can become cancerous. A four-year study of Vitamin D and calcium supplementation demonstrated a 60% drop in the incidence of cancer among a test group of postmenopausal women.

Doctors consider normal blood Vitamin D levels to be between 20 and 50 ng/ml (nanograms per milliliter). Less than 12 ng/ml is considered clinical Vitamin D deficiency.

40% of Americans get too little Vitamin D, while 10% are clinically Vitamin D-deficient. The general recommendation for Vitamin D3 supplementation is 1,000 IU (international units). Higher doses may be recommended, in consultation with a doctor, for patients with low levels of Vitamin D.

Doctors recommend Vitamin D supplementation for the winter months especially, and year-round for certain demographics at higher risk of Vitamin D deficiency, including pregnant women, people over the age of 65, people with darker skin tone, and people who get little exposure to direct sunlight. 

What is magnesium and why does your body need it?

Magnesium is a mineral. If you remember chemistry class, it’s on the periodic table under the symbol “Mg”. Specifically, it is an alkali earth metal.

Like the metals iron, calcium, and zinc, magnesium plays an important role in bodily functions and overall health. About 25 grams of magnesium, more than half of it stored in the skeletal system, can be found in a healthy adult human body. The mineral is involved in over 300 enzyme reactions and over 600 cellular reactions.

Humans absorb and replenish their body’s supply of magnesium by eating foods rich in magnesium, like almonds, cashew nuts, and spinach. 

Like many crucial vitamins and minerals, magnesium is a mineral that many Americans do not get enough of. Magnesium is one of seven essential macrominerals, minerals which humans need to consume in relatively large amounts—100 mg or more—to maintain optimal health.

Doctors estimate that over 68% of Americans are magnesium-deficient. Moreover, they associate magnesium deficiency with an increased risk of a range of conditions, including Alzheimer’s disease, Type II diabetes, migraine headaches, and cardiovascular disease. 

Optimal magnesium levels affect the following bodily functions:

Bone Health

Magnesium plays both direct and indirect roles in maintaining healthy bones. It directly contributes to bone density and bone crystal formation. It also helps regulate Vitamin D levels, which, as discussed above, play a critical role in calcium absorption.

Muscle Health

Magnesium binds to muscle cells to help them relax, counteracting the contracting effects of calcium. Magnesium deficiency can make it hard for the muscle cells to relax, leading to cramping and spasms.

Glucose Control and Insulin Metabolism

Magnesium plays an important role in blood glucose control and insulin metabolism. Low magnesium may contribute to insulin resistance, a precursor to Type II diabetes.

Heart Health

As mentioned, magnesium contributes to muscle health, and the heart is mostly muscle. Many people who suffer from congestive heart failure are magnesium-deficient. Treatment with magnesium helps lower the mortality rate of heart attack patients and may reduce the risk of cardiac arrhythmia.

Brain Health

Magnesium is found in the N-methyl-D-aspartate (NMDA) receptors of healthy adult brains, preventing neurons from being unnecessarily stimulated by weak signals. Overstimulation of the neurons can lead to brain damage.

Sleep Cycle

Studies have demonstrated the tendency of older adults who supplement with magnesium to sleep better. Animal studies have also shown the ability of magnesium to regulate melatonin production.

Blood Pressure Management

Studies have shown that magnesium supplementation preceded a drop in blood pressure, in both hypertensive subjects and subjects with blood pressure already in normal ranges.

Migraine Headache Management

Magnesium deficiency can inhibit neurotransmitters and constrict blood vessels, which can provoke a migraine headache in people susceptible to them. The American Migraine Foundation recommends 400-500 mg of magnesium supplementation per day to prevent migraines.

Premenstrual Syndrome Management

Some studies have indicated a capacity for magnesium, stacked with Vitamin B-6, to reduce the symptoms of PMS. The American College of Obstetricians and Gynecologists recommends magnesium supplementation to combat mood changes, breast tenderness, and bloating in women suffering from PMS.

Anxiety and Depression Management

Magnesium deficiency has been correlated with increased levels of clinical mood disorders, including depression and anxiety. This may be related to its effect on activity in the hypothalamic-pituitary-adrenal (HPA) axis, but this effect is not well understood.

When and why do people take magnesium supplements?

People of all ages take magnesium supplements for a variety of reasons. Magnesium is safe to consume and readily available as an over-the-counter supplement. A doctor may recommend magnesium supplementation, or a patient may take magnesium of their own accord as a preventative or to treat a particular condition.

Reasons to supplement with magnesium might include:

  • Known magnesium deficiency
  • Promote heart health, either as a preventative or after a cardiac event.
  • Prevent cancer in patients with a family history of certain cancers, like breast or colon cancer
  • Regulate blood pressure, either as a preventative measure or for patients with hypertension
  • Regulate blood glucose and insulin metabolism, as a preventative or for diabetic or prediabetic patients
  • Promote good bone health, especially in patients susceptible to bone disorders like osteoporosis
  • Promote good brain health, especially in patients susceptible to Alzheimer’s disease.
  • Treat various forms of inflammation
  • Treat symptoms of PMS
  • Prevent migraine headaches
  • Treat chronic fatigue
  • Treat fibromyalgia
  • Treat cramps and muscle spasms
  • Treat sleep disorders like insomnia or restless leg syndrome
  • Treat or prevent mood disorders like depression or anxiety
  • Treat or prevent constipation, heartburn, and/or indigestion

Vitamin D3 and magnesium ratio: things to consider

Since they work together, it is important to get the ratio of Vitamin D and magnesium correct when supplementing. The best course of action is to test your Vitamin D and magnesium levels and consult your doctor before beginning a supplementation regimen.

Here are some things to keep in mind when considering dosing ratios of Vitamin D and magnesium.

The recommended dosage of Vitamin D supplementation varies based on the age of the patient. The rough breakdown is as follows:

  • 0—1 year: 10 mcg (400 IU)
  • 1–13 years: 15 mcg (600 IU)
  • 14–70 years: 15 mcg (600 IU)
  • 71 years and older: 20 mcg (800 IU)
  • Pregnant and breastfeeding women: 15 mcg (600 IU)

While Vitamin D toxicity cannot be caused by overexposure to sunlight, it can result from over-supplementation. Doctors also recommend a daily upper limit of supplementation, which again varies by age:

  • 0—1 years: 25 mcg to 38 mcg (1,000 to 1,500 IU)
  • 1–13 years: 63 mcg to 75 mcg (2,500 to 3,000 IU)
  • 14 years and older: 100 mcg (4,000 IU)
  • Pregnant and breastfeeding women: 100 mcg (4,000 IU)

Vitamin D toxicity springs from over-calcification of the veins. Symptoms include nausea, frequent urination, fatigue, bone pain, and kidney stones.

As far as magnesium goes, doctors recommend the following doses of magnesium, with variations between the sexes at older ages:

  • 1–3 years: 65 mg
  • 4–8 years: 110 mg
  • 9 years and older: 350 mg

Over-supplementation with magnesium can lead to hypermagnesemia. Early symptoms of hypermagnesemia include nausea, vomiting, hypotension (excessively low blood pressure), flushing, urine retention, ileus, depression, and lethargy. 

Symptoms of advanced hypermagnesemia include breathing trouble, extreme hypotension, muscle weakness, irregular heartbeat, and cardiac arrest. Fatal hypermagnesemia has been observed in very young or very old subjects.

Do you need magnesium to absorb vitamin D?

The essential vitamins and minerals do not act alone. Many of them work together, in complex interrelations, to do their jobs in maintaining a healthy body.

Recent studies have shown that if a person is deficient in magnesium, no amount of Vitamin D3 supplementation will allow a patient to realize the health benefits of adequate Vitamin D. Magnesium is a critical factor in making Vitamin D bioavailable. Without magnesium present, Vitamin D is stored in the body and not used.

The body depends on magnesium to convert Vitamin D into its active form within the body. Magnesium also helps Vitamin D bind to its target proteins, as well as helping the liver and the kidneys to metabolize Vitamin D.

This research shows that supplementing with Vitamin D is pointless if a patient is deficient in magnesium—in fact, as the next section will explain, it may actually have harmful side effects to overload your system with Vitamin D without banking the magnesium needed to use it.

Why you cannot skip magnesium when you are already taking vitamin D

Patients who know or suspect that they are deficient in their Vitamin D levels may be tempted to supplement with Vitamin D3. They may already be supplementing. But if they are not also supplementing with magnesium, they could be doing more harm than good

Remember, magnesium deficiency prevents the body from using the Vitamin D you are supplementing it with. Additionally, the Journal of the American Osteopathic Association points out that people with low magnesium levels who supplement with Vitamin D show markedly higher levels of calcium and phosphorus. This is probably due to the role that activated Vitamin D plays in the absorption of calcium into the bones and other tissues.

Excess calcium in the bloodstream can lead to calcification of the inside of the arteries, resulting in poor cardiovascular health. Unabsorbed calcium can also cause nausea, frequent urination, fatigue, and kidney problems like kidney stones.

Before starting a Vitamin D and magnesium supplementation regimen, it is worth discovering whether or not your magnesium levels are deficient first. People considering starting a Vitamin D3 regimen without the advice of a doctor should consider supplementing with magnesium as well to prevent the adverse effects of unabsorbed calcium.

How can you tell if you are not getting enough Vitamin D?

The easiest way to determine whether or not you are getting enough Vitamin D and magnesium is to have your blood examined for the 25-hydroxyvitamin D biomarker. Blood can be collected at a local clinic or doctor’s office or using a home collection kit.

Without testing your blood, certain signs and symptoms might point to Vitamin D deficiency. Warning signs to look out for include:

Frequent Illness

Vitamin D helps your immune system fight off infection by viruses and bacteria. If you find yourself afflicted by frequent colds, bacterial infections, or other illnesses, a lack of Vitamin D could be inhibiting the ability of your immune system to do its job.


Fatigue can be a symptom of many conditions, but low Vitamin D is an oft-overlooked factor. Fatigue has been observed most frequently in young women as a sign of low Vitamin D.

Back and Bone Pain

Vitamin D helps the body absorb calcium. Insufficient calcium uptake can lead to bone and back pain, especially in older women.

Depression or Anxiety

Low Vitamin D is linked to seasonal affective disorder, which occurs in the winter months when Vitamin D-producing sunlight is not available. Mood disorders like depression or anxiety could be a sign of low Vitamin D.

Slow Wound Healing

Test tube studies have shown that lack of Vitamin D inhibits the creation of compounds necessary for the wound-healing process. It also plays a role in fighting infection and controlling inflammation. Slow wound healing due to low Vitamin D has been observed in dental patients and diabetic patients with foot injuries. 


Loss of Bone Mass

Back pain and easily-fractured bones are a sign of loss of bone mass. Since Vitamin D helps bones absorb calcium, too little Vitamin D could be the culprit for a loss of bone mass. 

Hair Loss

Hair loss can result naturally from stress, age, and genetics, but vitamin deficiencies can also trigger hair loss. Vitamin D deficiency has been correlated with hair loss in women, but observations have been inconclusive.

Muscle Pain

Muscle pain has many potential causes, but one study discovered that 71% of people with chronic pain also had low Vitamin D. 

Signs your body needs more magnesium

In a sense, the signs of Vitamin D deficiency all apply to magnesium deficiency. Remember, low magnesium means that your body can’t process Vitamin D. As a result, people with low magnesium might exhibit symptoms of vitamin D deficiency, even if their body contains plenty of Vitamin D. 

Symptoms unique to magnesium deficiency include:

Muscle Cramping and Twitching

Magnesium plays a key role in the relaxation of muscle cells. Without the relaxing influence of magnesium, the muscles are susceptible to cramping and involuntary twitching.

Mental Disorders

Low levels of magnesium are associated with depression and apathy. They may be susceptible to anxiety, but evidence for this connection is not strong. 


Osteoporosis is a condition of reduced bone density, resulting in back pain and brittle bones susceptible to fracture. Many conditions contribute to osteoporosis, but magnesium deficiency is one of them. 


Muscle Weakness

Magnesium deficiency is believed to result in reduced potassium uptake, resulting in insufficient potassium content in the muscles. This can lead to muscle weakness, also known as myasthenia. 


High Blood Pressure

While studies are not conclusive, low magnesium levels may result in elevated blood pressure.



Severely asthmatic people often present with low magnesium levels. Magnesium sulfate inhalers are frequently prescribed to asthmatics.


Irregular Heartbeat

Low magnesium levels have been shown to cause cardiac arrhythmia, a potentially life-threatening heart condition. 


When to see a doctor

If you exhibit any of the symptoms of low Vitamin D and magnesium levels, it is worth going to the doctor’s office or getting your levels checked with a home test.

If your tests return low levels of Vitamin D, consider consulting your doctor for recommendations of how much Vitamin D and magnesium to supplement with. Both supplements are available over-the-counter without a prescription, but a doctor can advise you as to the proper proportions of supplementation for each nutrient.

Updated on
October 21, 2021
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