Magnesium is one of our favourite supplements to recommend because it plays a vital role in nearly every system of the body. From energy production and muscle recovery to sleep quality and brain health, this mineral is a true multitasker. Yet despite its importance, there’s a lot of confusion about which forms of magnesium to take, how much is actually effective, and whether popular products are worth the money. In this post, we’ll break down the science, cut through the marketing noise, and share clear, practical guidance on choosing and dosing magnesium. You’ll also get our exact recommendations for the forms we trust and why they work, so you can confidently add magnesium to your daily routine and feel the benefits where they matter most.

• Why magnesium matters
• How much magnesium should you take? Understanding the supplemental upper limit
• Dividing doses: why spacing magnesium matters
• Forms of magnesium: organic versus inorganic
• Magnesium threonate: the brain supplement everyone talks about
• Elemental magnesium and why it matters for counting your dose
• Practical dosing strategies and what I recommend
• How I personally supplement magnesium
• Special situations and interactions you need to know
• How to calculate your magnesium from food and supplements
• Transdermal magnesium and Epsom salt baths
• Practical product selection checklist
• How to approach magnesium if you have a specific goal
• Common myths and misconceptions
• FAQ
• Summary and final practical plan
• Closing thoughts

Magnesium is an essential mineral involved in hundreds of enzymatic reactions. It helps regulate nerve and muscle function, supports energy production, contributes to healthy sleep and mood, and is involved in bone and cardiovascular health. Despite its importance, a large portion of the U.S. population does not get enough magnesium from food alone. If your diet is low in dark leafy greens, nuts, seeds, whole grains, and legumes, a supplement can make sense.

But not all magnesium supplements are created equal. Different chemical forms have different absorption profiles, different amounts of elemental magnesium, and different side effect profiles. The choices you make should be guided by your health goals, your tolerance for gastrointestinal side effects, and whether you have any medical conditions that affect magnesium handling, like kidney disease.

The US Institute of Medicine’s Food and Nutrition Board sets the tolerable upper intake level (UL) for supplemental magnesium at 350 milligrams per day. This guideline refers specifically to magnesium from supplements and medications, not the magnesium you consume in food. The reason for this distinction is simple: the first sign of excess supplemental magnesium is diarrhea or other gastrointestinal upset. Magnesium salts are used therapeutically as laxatives for this exact reason.

Here are the practical implications:

• I recommend treating 350 mg per day of supplemental elemental magnesium as the safe default maximum for most people unless advised otherwise by a clinician. This is the amount at which most people avoid diarrhea and GI distress.
• Magnesium from food does not count toward that 350 mg supplemental cap. If you eat magnesium-rich foods you can consume additional magnesium without increasing the risk for supplement-induced diarrhea in most cases.
• Some people tolerate higher supplemental doses without trouble, and some research suggests dietary magnesium above the RDA may be beneficial. But for safety and simplicity I encourage most individuals to stay at or below 350 mg supplemental elemental magnesium daily unless under medical supervision.

Recommended daily allowances (RDA) for magnesium

To put the supplemental limit in context, the RDA for elemental magnesium varies by sex and age. To summarize the typical adult RDAs:

• Adult men 19 to 30 years: around 400 mg per day; men over 31: 420 mg per day
• Adult women 19 to 30 years: around 310 mg per day; women over 31: 320 mg per day
• Pregnant and lactating women have higher needs

These RDA numbers reflect total magnesium from foods plus supplements. Because the tolerable upper intake level of supplemental magnesium is 350 mg, many people reach their RDA by combining dietary magnesium with a modest supplemental dose.

Magnesium absorption is not linear. Taking a large single dose is less efficient than splitting that same amount into multiple smaller doses throughout the day. Practically speaking, smaller, spaced doses accomplish three things:

• They increase the fraction of magnesium absorbed by the gut.
• They reduce the chance of gastrointestinal side effects such as loose stools or cramping.
• They provide a steadier supply for the body to use across the day and night.

So if your target supplemental elemental magnesium is 300 milligrams per day, take 100 mg three times per day, or 150 mg twice per day, not a single 300 mg tablet once daily. If you primarily want magnesium for evening relaxation and sleep, you can take a portion of your supplemental dose in the evening and the rest earlier in the day.

This is a critical topic. In the supplement world magnesium is sold in many chemical forms. The two broad categories I use here are organic magnesium salts and inorganic magnesium salts.

Organic magnesium salts

By organic we mean that the magnesium is bound to an organic acid or compound that contains carbon. Common organic forms include magnesium citrate, magnesium glycinate (also called magnesium bisglycinate), magnesium taurate, and magnesium malate. Clinical research generally supports that these organic magnesium salts are better absorbed and more effective at raising plasma magnesium levels than many inorganic forms. For that reason, they are preferable for addressing deficiency and for general supplementation.

Additional advantages:

• Magnesium glycinate tends to be gentle on the stomach. It is often my default recommendation if GI tolerance is a concern. It can also provide the amino acid glycine, which itself has calming effects for some people.
• Magnesium taurate couples magnesium with taurine, an amino acid that may have cardiovascular and neuromodulatory benefits. If heart rhythm or blood pressure is a concern, some people choose this form because of the potential additive effects of taurine.
• Magnesium malate is sometimes chosen for fatigue and muscle pain because malic acid participates in energy metabolism. People report subjective benefits for muscle soreness and energy, but strong clinical trials are limited.

Inorganic magnesium salts

Examples of inorganic forms include magnesium oxide, magnesium chloride, and magnesium sulfate. Magnesium oxide is a very common inexpensive form and it contains a relatively high percent of elemental magnesium by weight. However, bioavailability is poorer compared to the organic salts, which means more of the magnesium may pass through the gut unabsorbed and potentially cause diarrhea.

Magnesium sulfate is often encountered as Epsom salt for baths. When taken orally in high amounts it also acts as a laxative. People commonly take Epsom salt baths believing magnesium will passively absorb through the skin. The evidence for meaningful transdermal absorption from bath water is very limited and far from conclusive. You can certainly enjoy a warm Epsom salt bath for relaxation and muscle comfort, but do not assume you are reliably boosting your magnesium status by soaking unless there is clear evidence to support that in your case.

Magnesium threonate has gotten a lot of attention in recent years because some animal studies suggest it may increase brain magnesium levels more effectively than other forms and might improve cognition. The logic is attractive: magnesium is tightly regulated in the central nervous system, and if a supplement could cross the blood brain barrier and modestly raise magnesium inside the brain, it might affect learning, memory, and even pathways related to neurodegeneration.

How magnesium threonate is different chemically:

• Magnesium threonate is magnesium chelated to threonic acid, which is a metabolite of vitamin C. The idea is that this chelation changes the molecule’s transport properties and may facilitate passage across cellular membranes including the blood brain barrier.
• Animal data: in mice, very high relative doses of magnesium threonate were associated with small improvements in cognition and reductions in amyloid beta plaques in some studies. The human equivalent doses used in those mouse studies, when converted by body weight, are quite large.

There are a few important caveats to emphasize before you consider magnesium threonate a brain wonder supplement:

1. Most magnesium that you ingest is regulated by active transport mechanisms at the gut and at the blood brain barrier. The body maintains a high-magnesium-to-low-cerebrospinal-fluid gradient as a way to tightly control neuronal excitability and other functions. For example, increasing blood magnesium by 300 percent in humans was associated with less than a 19 percent change in cerebrospinal fluid magnesium concentration. That tells you the body vigorously controls how much magnesium gets into the brain.
2. Animal studies are intriguing but not conclusive for humans. While a mouse study may show cognitive benefits at high equivalent doses, translating those results to human therapy needs careful clinical validation.
3. Human trials to date are limited in number, small in size, and in some cases industry funded. That increases the need for caution when interpreting positive findings.

What the human studies actually show

There are only a few human studies exploring magnesium threonate.

The 2016 study that popularized magnesium threonate was a small trial with 44 participants. The authors used a marketed formula often referred to as Magtein and dosed participants based on body weight, with daily doses around 1500 to 2000 milligrams of magnesium threonate. The results were underwhelming in several respects:

• Only a marginal increase in plasma magnesium occurred. There was no increase in red blood cell magnesium compared to placebo.
• Urinary magnesium rose significantly in the treatment group, suggesting a substantial portion of the magnesium was excreted rather than being retained in the body.
• When each of the four cognitive tests were analyzed separately there were no significant differences between groups. The authors reported a statistically significant improvement when all four tests were combined into a composite measure, which raises concerns about the robustness of the finding given the small sample size.

A later 2022 trial involved 100 participants. That trial provided the treatment group with 400 mg of magnesium threonate plus vitamins C, D, B6, and phosphatidylserine. The placebo group received inert starch. The treatment group improved on cognitive tests compared to placebo, but this design introduces a major confounder: the active group received a multi-ingredient combination, not magnesium threonate alone. In other words, we cannot attribute the cognitive benefit specifically to magnesium threonate because the added vitamins and phosphatidylserine may have contributed, alone or synergistically.

For these reasons my interpretation is conservative: magnesium threonate has interesting theoretical promise, but current human evidence is not strong enough to declare it a reliable route to increase brain magnesium or to improve cognition. Additionally, magnesium threonate contains a relatively low amount of elemental magnesium, so it is not a good vehicle for meeting your daily magnesium requirements.

When you read supplement labels, manufacturers often list the total weight of the compound (for example magnesium citrate 400 mg). What matters physiologically is the amount of elemental magnesium contained within that compound. Different forms contain different percentages of elemental magnesium. This difference matters because you need to know how much elemental magnesium you are actually ingesting relative to the 350 mg per day supplemental upper limit and relative to your RDA.

A particularly important point is that magnesium threonate provides a low amount of elemental magnesium per capsule or gram of compound. Even if you take a large number of milligrams of magnesium threonate, the elemental magnesium you get may be small. For that reason I do not count magnesium threonate toward daily RDA goals. If your priority is meeting your RDA, choose a supplement that provides a meaningful amount of elemental magnesium per dose such as magnesium glycinate, magnesium citrate, or a mixed-form product that explicitly lists elemental magnesium.

Here is the practical strategy I use and recommend for most people who want to safely improve their magnesium status without GI side effects.

1. Estimate dietary magnesium first. Look at your typical meals and identify magnesium-rich foods like spinach, Swiss chard, almonds, pumpkin seeds, black beans, and whole grains. Use nutrition labels or a reputable app to estimate how much magnesium you get from food. Subtract that from your RDA target to see how much supplemental elemental magnesium you need to reach the RDA.
2. If you choose to supplement, favor organic magnesium salts such as magnesium glycinate, magnesium citrate, magnesium taurate, and magnesium malate. These are generally better absorbed and better tolerated.
3. Stay at or below 350 mg of supplemental elemental magnesium per day unless you are under direct medical supervision. Split the dose into multiple smaller amounts during the day to maximize absorption and minimize GI effects.
4. If you are taking magnesium for sleep or relaxation, I often take a portion of the dose in the evening, typically 100 to 200 mg of elemental magnesium as glycinate to reduce the chance of GI disturbance while benefiting from glycine’s calming properties.
5. If you are supplementing for constipation, magnesium citrate or magnesium sulfate in higher doses will produce a laxative effect. Avoid those forms for routine daily supplementation if your goal is nutritional repletion rather than bowel evacuation.
6. Do not rely on magnesium threonate to meet your RDA. If you want to use magnesium threonate for potential cognitive benefits, treat it as an adjunct, not as your primary magnesium source.

These recommendations align with the most conservative safety guidance while allowing flexibility for individual preference and goals.

If you’d like guidance on weaving magnesium into a broader wellness plan, our Integrate Program can help you build a sustainable, evidence-based daily routine.

When it comes to magnesium, I like to keep it simple and effective. My go-to choice is CanPrev’s Magnesium Bis-Glycinate 200 Gentle available as part of our BetterLife VIP Protocols. Each serving provides a gentle, highly absorbable form of magnesium that supports relaxation, deeper sleep, muscle recovery, and energy metabolism.

I typically take 2 capsules per day, which gives me the optimal dose without digestive discomfort. Because it’s magnesium bis-glycinate, it’s well tolerated, easy on the gut, and offers the added benefit of glycine — an amino acid that can help promote calmness and support sleep quality.

If you’re looking for a trusted, research-backed magnesium supplement that delivers real results, CanPrev is the one I recommend.

Before you start any supplement regimen there are a few safety flags and interactions you should consider.

Kidney disease

If you have impaired renal function, do not supplement magnesium without medical supervision. The kidneys are the primary route of magnesium excretion; reduced kidney function can lead to magnesium accumulation and toxicity if supplements are taken inappropriately.

Medications

Magnesium can interact with certain medications. A few important examples:

• Antibiotics such as tetracyclines and fluoroquinolones can chelate with magnesium and reduce absorption of the antibiotic. If you take one of these classes of antibiotics, separate magnesium supplements and the antibiotic by at least two hours.
• Bisphosphonates for osteoporosis can have reduced absorption if taken near magnesium-containing supplements. Space dosing as advised by your clinician or pharmacist.
• Certain diuretics affect magnesium handling and could either raise or lower magnesium levels. Check with your physician.

Testing magnesium status

Serum magnesium is convenient but it is not the best marker for total body magnesium. The body maintains serum magnesium within a narrow range even when intracellular magnesium is low. Tests that can be more informative include red blood cell magnesium, ionized magnesium, or intracellular magnesium panels, though these are not always available or standardized.

If you suspect deficiency—symptoms can include muscle cramps, weakness, fatigue, irregular heart rhythm, or sleep issues—work with a clinician who can order the appropriate tests and interpret them in the context of your clinical picture.

Since individual genetics can influence how your body absorbs and uses magnesium, you may benefit from exploring personalized DNA insights to see how your unique biology shapes your supplement needs.

Do a quick inventory:

1. Estimate daily magnesium from food using an app or nutrition database. Key foods include dark leafy greens, pumpkin seeds, almonds, cashews, beans, and whole grains.
2. Decide how much supplemental elemental magnesium you want to take. My default is to top off dietary intake so total magnesium approaches the RDA for your age and sex, while keeping supplemental elemental magnesium at or below 350 mg per day.
3. If you use magnesium threonate, take it for potential brain benefits only and do not count it toward the supplemental total used to reach your RDA.

Example calculation:

• You are a 35 year old man with an RDA of around 420 mg/day.
• Your food provides approximately 200 mg/day of magnesium.
• You would aim to supplement around 220 mg of elemental magnesium per day to reach the RDA. Keep that 220 mg below the 350 mg supplemental upper limit.

Adjust the numbers for your age, sex, and actual dietary intake. If you have higher needs because of intense endurance training or certain health conditions, consult a clinician for personalized guidance.

People commonly use Epsom salt baths for muscle soreness and stress relief and claim they raise magnesium levels through the skin. The compound used in Epsom salt is magnesium sulfate. When taken orally it can act as a laxative. When used in bath water the idea is that magnesium will passively diffuse through the skin and increase body magnesium.

Reality check: the evidence for meaningful transdermal absorption from Epsom salt baths is weak. The skin is an effective barrier and while some trace magnesium may be absorbed, repeated high-quality research demonstrating clinically useful increases in systemic magnesium from baths is lacking. That does not mean you should avoid Epsom salt baths. Many people find them relaxing and helpful for muscle tension. Just do not rely on them as your primary method to correct a magnesium deficiency.

When you are shopping for a magnesium supplement, use this checklist:

• Look for forms: prioritize glycinate, taurate, citrate, or malate for general supplementation.
• Check the label for elemental magnesium per serving. Calculate how many milligrams of elemental magnesium you are getting per capsule or scoop.
• Plan to keep supplemental elemental magnesium at or below 350 mg/day unless directed otherwise by your clinician.
• Split doses across the day to improve absorption and tolerate higher total amounts if needed.
• If you want potential brain effects, you can try magnesium threonate but do not count that magnesium toward your RDA. Treat that product as an adjunctive therapy and be aware the evidence is limited.
• Check for extraneous ingredients or vitamins that might alter the outcomes. If a product contains multiple active vitamins or compounds they can confound the effects attributed to magnesium.

You can browse our curated BetterLife product collection for high-quality magnesium options that clearly list elemental magnesium content and use clinically effective forms.

Restore or prevent deficiency

Work out your dietary intake and supplement to reach your RDA while staying within the supplemental upper limit. Prefer organic salts. Consider taking magnesium with meals in divided doses for best absorption and tolerance.

Support sleep and relaxation

Magnesium glycinate is a common choice because glycine may have calming properties. A typical approach is 100 to 200 mg of elemental magnesium as glycinate in the evening. Adjust based on your response and GI tolerance.

Relieve occasional constipation

Magnesium citrate or magnesium sulfate at higher doses will produce a laxative effect. These are not suitable for daily use for everyone. Use them intentionally for bowel clearance and not as the default magnesium supplement for nutrient repletion because the laxative effect may limit absorption and tolerability.

Brain health or cognition

If you are specifically targeting cognitive outcomes you can consider adding magnesium threonate as an adjunct, but be cautious. The evidence in humans is limited and mixed. If you choose to try it, remember: magnesium threonate contributes little elemental magnesium to your overall intake, so include another form for nutritional sufficiency.

• Myth: All magnesium forms are identical. Reality: Forms differ in bioavailability, elemental magnesium content, and side effects.
• Myth: Epsom salt baths reliably boost body magnesium. Reality: Evidence for transdermal absorption sufficient to correct deficiency is weak.
• Myth: Magnesium threonate is the only form that gets into the brain. Reality: Animal data suggest potential advantages but human evidence is limited and not definitive.
• Myth: If it is natural it cannot cause side effects. Reality: High supplemental magnesium causes diarrhea and can be problematic in kidney disease.

Q: How much supplemental magnesium should I take each day?

A: The conservative approach is to keep supplemental elemental magnesium at or below 350 mg per day, the tolerable upper intake level set by the Institute of Medicine. Combine that with dietary magnesium to reach your RDA for total magnesium intake.

Q: Which form of magnesium should I buy?

A: For most people I recommend organic magnesium salts such as magnesium glycinate, magnesium citrate, magnesium malate, or magnesium taurate. Glycinate is gentle on the stomach and often my go-to. Taurate can be attractive if you want potential cardiovascular support. Avoid magnesium oxide as a long-term repletion strategy because it is less bioavailable.

Q: Can I take magnesium threonate for brain health?

A: You can try it, but be realistic about the evidence. Animal studies are promising in some respects, but human trials are limited and some are industry funded with confounding ingredients. Also do not count magnesium threonate toward your RDA because it contains little elemental magnesium. Use it as an adjunct rather than your primary magnesium source.

Q: Will an Epsom salt bath increase my magnesium levels?

A: The evidence for significant transdermal absorption from Epsom salt baths is not strong. Baths can be relaxing and helpful for muscle soreness but should not be relied on to correct magnesium deficiency.

Q: Can I take magnesium with other vitamins?

A: Yes in most cases, but be careful with combinations. Some trials that show cognitive benefits mixed magnesium threonate with vitamins and phosphatidylserine, making it impossible to attribute effects specifically to magnesium. Magnesium can also interact with certain medications, so check with your clinician.

Q: Is it safe to exceed 350 mg of supplemental magnesium?

A: Some people tolerate higher supplemental doses without GI issues, but the official tolerable upper intake level for supplemental magnesium is 350 mg/day. Going above that increases the risk of diarrhea and other GI symptoms. People with kidney disease should avoid higher doses unless supervised by a healthcare provider.

Q: How can I test if I am magnesium deficient?

A: Serum magnesium is not a sensitive marker for tissue deficiency. If deficiency is suspected, discuss more informative tests with your clinician such as red blood cell magnesium or other intracellular magnesium measures. Clinical symptoms and dietary assessment are also important pieces of the puzzle.

Here is the condensed action plan I use and recommend to readers who want a straightforward approach to magnesium:

1. Estimate your dietary magnesium intake and compare to the RDA for your age and sex.
2. If you need supplemental magnesium, choose an organic salt such as glycinate, citrate, malate, or taurate.
3. Keep supplemental elemental magnesium at 350 mg per day or less unless a clinician advises otherwise. Split the total into smaller doses across the day for better absorption and less GI upset.
4. If you are interested in potential brain effects, consider adding magnesium threonate as an adjunct but do not count it toward your RDA because it delivers limited elemental magnesium and human evidence is limited.
5. For sleep, magnesium glycinate taken in the evening is a reasonable choice. For constipation, magnesium citrate or sulfate will work as laxatives but are not ideal for chronic daily repletion due to their GI effects.
6. If you have kidney disease or are on interacting medications, consult your clinician before starting magnesium supplements.

My own regimen: I take a mixed-form magnesium product during parts of the day and a magnesium glycinate product at night. I keep my supplemental elemental magnesium within safe limits and monitor how I feel. 

Magnesium is a crucial but often overlooked nutrient. The right form, dose, and timing matter. Organic magnesium salts like glycinate, taurate, citrate, and malate offer better bioavailability and fewer GI side effects than many inorganic forms. Magnesium threonate is an interesting compound for brain health, but the human data are preliminary and it should not be counted toward your daily magnesium requirements. Keep supplemental elemental magnesium at or below 350 mg per day for safety and distribute that dose across the day for better absorption. If you have special medical circumstances consult with your clinician before changing your regimen.

If you want more personalized help, check out the resources I provide at Betterlife where I lay out my protocols for nutrients, sleep, and recovery in more detail. My goal is to make nutrient decisions simple and evidence based.

Take control of your magnesium—choose the form that matches your goals, dose it sensibly, and use high quality products that list elemental magnesium clearly on the label. That is the best way to be sure you are getting the benefit without the unnecessary side effects.