Content Library Articles Longevity Journal

The Best Forms of Magnesium—and When to Use Them

May 5, 2025

Magnesium doesn’t get the attention that vitamin D or omega-3s do, but it should. 

It’s involved in over 600 enzymatic reactions in the body—everything from your brain fires to how your heart keeps rhythm. It even helps regulate your mood, hormones, blood sugar, and sleep.

And yet, most people aren’t getting enough. Maybe even you.

At least 20% of people are clinically deficient in this essential mineral—and up to 80% may be living with low levels that never get flagged but still cause problems.^1,2

That might show up as muscle cramps, brain fog, anxiety, trouble sleeping, PMS, or constipation. Or it might just feel like your body isn’t running as smoothly as it could. 

Worse, long-term deficiency has been linked to higher risks of serious conditions like type 2 diabetes, heart disease, high blood pressure, stroke, and even early death.

Turns out, processed foods, chronic stress, caffeine, alcohol, certain medications, and our depleted soil all chip away at your levels. Over time, that gap adds up—and your body starts to feel it.

The good news? Magnesium supplements can help. But the moment you try to choose one, things get confusing fast. Magnesium citrate? Glycinate? L‑threonate? Something else?

In this quick guide, I’ll help you figure out whether you’re actually getting enough magnesium—and if not, which form makes the most sense for your body and your needs.

Are You Getting Enough Magnesium?

Unless you (or your doctor) knows the right test to order, you probably can’t be sure.

Here’s why: Although magnesium is included in standard blood tests like the basic or comprehensive metabolic panel, the specific test used—called “serum magnesium”—doesn’t tell the full story.

That test only looks at the tiny amount of magnesium circulating in your blood—just 1 percent of what’s in your body. The other 99% is stored in your muscles, bones, and tissues.

Your body works hard to keep your blood levels of magnesium stable. It’ll pull magnesium from wherever it can—bone, muscle, even your cells—to make it look like everything’s fine. 

So unless you’re severely deficient, your test result may come back “normal,” even if your body is running low.

What you actually want is a red blood cell (RBC) magnesium test. This measures magnesium inside your cells, where it’s actually doing its job. 

It’s a better reflection of your long-term magnesium status—and it tracks more closely with symptoms.

You get this test as part of Function Health’s membership, which is one of the easiest and most comprehensive ways to get a full view of your health—including magnesium levels most doctors don’t check.

What kind of symptoms point to a magnesium shortfall? Pretty much anything that cramps, spasms, or feels overstimulated might be a clue. Some of the most common include:

• Muscle cramps or twitching
  
  
• Insomnia or restless sleep
  
  
• Anxiety, irritability, or mood swings
  
  
• Headaches or migraines
  
  
• PMS or menstrual cramping
  
  
• Constipation
  
  
• Blood sugar swings or insulin resistance
  
  
• Heart palpitations or high blood pressure
  
  
• Brain fog, memory issues, or trouble focusing
  
  
• Sensitivity to noise or light

If you’re experiencing one or more of these,  it could be due to a lack of magnesium.

What About Getting Magnesium from Food?

If your levels are low—or even just not optimal—the first question is usually: “Can’t I just get more from food?”

And yes, magnesium is found in real, whole foods. Dark leafy greens like spinach and Swiss chard, pumpkin seeds, cashews, almonds, avocado, even dark chocolate—all of these are naturally rich in magnesium.

But here’s the catch: It’s harder than it used to be to get enough from food alone.

Modern farming practices have stripped magnesium from the soil, which means even healthy produce has less than it used to.

Between 1940 and 1991, magnesium levels in vegetables dropped by 23%, then partially rebounded—yet still remain nearly 10% lower overall than they were in 1940.³

Food processing also removes magnesium—up to 80% can be lost in milling or refining.⁴ And certain compounds in plant foods (like phytates) can bind to magnesium and block absorption.

On top of that, your body burns through magnesium faster when you're under stress, drinking coffee or alcohol, or taking certain medications.

So yes—diet matters. But for many people, food isn’t enough to close the gap.

That’s where the right supplement can make all the difference.

Choose the Right Magnesium Supplement 

Which magnesium supplement should you take? I’ll walk you through the top forms—the ones I recommend most often—and help you figure out which one makes the most sense for your body.

Most people do well with a daily dose of 400 to 500 mg of magnesium from supplements, though some may need more depending on symptoms and individual needs. It’s best to start low and increase gradually, especially if you take magnesium citrate and are sensitive to laxative effects. 

Magnesium Glycinate: The All-Purpose Calmer

If you’re not sure where to start, this is often the best bet. Magnesium glycinate is well absorbed, gentle on your stomach, and doesn’t have a laxative effect—unlike some other forms such as citrate.

The “glycinate” part refers to glycine, an amino acid that has a calming effect on your brain. That’s part of why this form of magnesium works so well for sleep, anxiety, and stress. But it also supports cardiovascular health, blood pressure, PMS symptoms, and bone strength.

It’s a solid choice for anyone who feels wired, tense, or burned out—or who just wants broad support without a lot of trial and error.

When to consider it: 

• Trouble falling or staying asleep
  
  
• Feeling anxious, edgy, or overstimulated
  
  
• High blood pressure or cardiovascular risk
  
  
• PMS, cramping, or mood swings
  
  
• Low energy or ongoing fatigue

Best taken at night, since it helps the body wind down.

My recommendation: Magnesium Glycinate by Pure Encapsulations

Magnesium Citrate: The Gentle Mover

This one’s simple. If you’re backed up, magnesium citrate can help get things moving. It draws water into your intestines, softens stool, and can gently relieve constipation.

It’s also well absorbed and easy to find, but the laxative effect means it’s not ideal for long-term daily use—unless you’re using a small dose for regularity, and it works for your body.

When to consider it:

• Occasional constipation
  
  
• Feeling bloated or sluggish
  
  
• Traveling and want to stay regular
  
  
• You get “backed up” when you make a change from ultra-processed foods to whole foods (like with the  10-Day Detox)
  
  
• You know you need magnesium but want a side benefit of digestive support

My recommendation: Magnesium Citrate by Pure Encapsulations

Just start low and ease up if it’s too much. A little goes a long way.

Magnesium L‑Threonate: The Brain Supporter

If your focus is cognitive health—memory, learning, mental clarity—this is the one to know. 

Magnesium l‑threonate is a newer form designed to cross the blood-brain barrier more effectively than others, meaning more magnesium actually reaches your brain.

It’s also being looked at for its potential to support sleep and reduce anxiety. The research is still early, especially in humans, but it’s promising—particularly for those dealing with brain fog, age-related memory changes, or stress that hits their cognition hard.

When to consider it:

• Brain fog or trouble focusing
  
  
• Memory concerns
  
  
• Chronic stress or anxiety that feels mental more than physical
  
  
• Sleep issues that don’t respond to other approaches

Best taken in the evening—or split between afternoon and night—depending on how it affects your focus and sleep.

My recommendation: Neuromag (Magnesium L-Threonate) by Designs for Health

References

1. Guillaume T, Krzesinski JM. Management of serum magnesium abnormalities. Rev Med Liege. 2003 Jul;58(7–8):465–7. 

2. Touvier M, Lioret S, Vanrullen I, Boclé J-C, Boutron-Ruault M-C, Berta J-L, et al. Vitamin and mineral inadequacy in the French population: estimation and application for the optimization of food fortification. Int J Vitam Nutr Res. 2006 Nov;76(6):343–51. 

3. Mayer A-MB, Trenchard L, Rayns F. Historical changes in the mineral content of fruit and vegetables in the UK from 1940 to 2019: a concern for human nutrition and agriculture. Int J Food Sci Nutr. 2022 May;73(3):315–26. 

4. Cazzola R, Della Porta M, Manoni M, Iotti S, Pinotti L, Maier JA. Going to the roots of reduced magnesium dietary intake: A tradeoff between climate changes and sources. Heliyon. 2020 Nov;6(11):e05390.