You’re Probably Not Getting Enough Magnesium—Here’s What To Do About It
This guide breaks down what magnesium actually does, why deficiency is so easy to miss, and how to fix it with food, smarter testing, and the right supplement strategy.
Recently, I started working with a marathoner who was constantly feeling overtrained—crashing mid-workout, waking up tired, and struggling with nagging muscle cramps and restless sleep. His bloodwork looked within normal ranges when they came back from the labs but his recovery scores, mood, and energy told a different story. When we ran a red blood cell magnesium test, he was borderline deficient. Within weeks of dialing in his intake—mostly through magnesium glycinate—his HRV jumped, sleep normalized, and training metrics rebounded. I see this all the time with clients and its severely under-discussed.
Magnesium doesn’t get the spotlight like vitamin D or omega-3s, but it should. This often-overlooked mineral is foundational for hormone balance, stress resilience, energy metabolism, and recovery. It activates over 600 enzymatic reactions in the body, many of which are essential for athletic performance and long-term health. And most people—especially active ones—aren’t getting enough.
Why Magnesium Matters More Than You Think
Magnesium is crucial for sending signals between your nerves and muscles, making energy at the cellular level, keeping hormones in check, and balancing your stress and relaxation responses. Yet "normal" serum levels in the population don’t reflect optimal function. That’s because serum magnesium represents less than 1% of total body stores and is tightly regulated by the kidneys. Subclinical magnesium deficiency, where serum levels appear "normal" but intracellular stores are depleted, is both common and consequential. This gets at a key distinction between conventional and functional health: where traditional medicine may rely on lab ranges to rule things out, functional approaches look at whether your body is actually working well—even if your labs are technically "normal."
For people who train hard and exercise frequently, magnesium loss adds up quickly through sweat, increased metabolic demand, and often from not getting enough through food. If you're dealing with things like lingering fatigue, muscle cramps, restless sleep, or anxiety—especially despite "normal" lab results—it might be worth looking at magnesium.
Five Core Roles of Magnesium in the Body
Hormone Regulation Magnesium helps your body respond better to insulin, keeps inflammation in check, and makes it easier to manage blood sugar levels. A meta-analysis by Veronese et al. (2021) showed significant improvements in fasting glucose and insulin sensitivity with magnesium supplementation. It also modulates sex hormones: higher magnesium is associated with increased free testosterone in men (Maggio et al., 2011), and supplementation improved testosterone by ~30% in athletes (Brilla & Conte, 2000). In women, magnesium can also ease PMS symptoms and stabilize estrogen/progesterone fluctuations.
HPA Axis and Stress Response Magnesium helps regulate the brain and adrenal systems that control your stress hormones—like cortisol—keeping your stress response balanced instead of constantly revved up. Magnesium deficiencies can amplify your stress reactivity, reduce HRV, and increase cortisol. Supplementation has been shown to lower serum cortisol (Zogović et al., 2014) and improve the body's ability to shift into a relaxed, recovery-focused state (Wienecke & Nolden, 2016). For high-performers, this translates to better stress resilience and recovery.
Muscle Function Magnesium is a calcium antagonist and therefore key for muscle relaxation. It helps calm overactive nerves, keeps your muscles from locking up, and ensures the right balance of minerals for smooth muscle function. Deficiency can be linked to cramps, spasms, and fatigue. In athletes, even a marginal deficiency raises heart rate and oxygen cost of exercise (Lukaski, 2001).
Sleep and Recovery Magnesium enhances GABA signaling, supports melatonin production, and reduces evening cortisol. All of these functions directly impact how quickly you fall asleep, how deeply you sleep, and how refreshed you feel the next day. Supplementation improves sleep onset, duration, and architecture. In a study by Abbasi et al. (2012), 500 mg of elemental magnesium nightly improved sleep efficiency and reduced insomnia scores in older adults.
Mitochondrial Function and ATP Synthesis Magnesium is essential for how your body makes and uses energy. Almost all of your ATP—the main energy molecule used by your cells—is attached to magnesium. Without enough magnesium, your mitochondria (your cells' power plants) don't work as well, your energy drops, and you produce more oxidative stress. Low levels can leave you feeling tired and sluggish. When magnesium levels are restored, people often see better endurance, improved oxygen use, and less fatigue during workouts (Golf et al., 2018).
Testing Magnesium Status: The Tricky Part
Most standard lab tests measure serum magnesium, which is the magnesium floating in your blood. But the catch is that serum levels only represent about 1% of your total magnesium and are tightly regulated by your body, even if your overall stores are low. That means your results can look "normal" on paper, even when you're functionally deficient. Better testing options include RBC (red blood cell) magnesium and, if available, ionized magnesium, which give a more accurate picture of what's actually available in your cells. Signs of low magnesium, even when labs look fine, include poor sleep, fatigue, cramps, anxiety, and blood sugar swings. In functional health, we typically aim for RBC magnesium levels above 6.0 mg/dL for optimal performance and recovery.
Optimizing Magnesium Intake: Food and Supplements
Top Food Sources:
Start with food first. Like most nutrients, magnesium is best absorbed and used by the body when it comes from whole, nutrient-dense foods. Supplements can help fill gaps, but they’re not a substitute for a solid diet.
Leafy greens (spinach, chard)
Nuts and seeds (pumpkin, almonds)
Legumes
Dark chocolate
Soil depletion and food processing reduce magnesium content in modern diets, and many athletes follow low-magnesium diets (e.g., low-carb, processed).
Supplementation: Forms and Use Cases
Start with 200–400 mg of elemental magnesium per day, divided into two doses. When choosing a supplement, always check the label for the amount of elemental magnesium—the actual usable magnesium in the product—not just the total compound weight (which can be misleading). For example, 500 mg of magnesium glycinate might only provide 100 mg of elemental magnesium.
Take magnesium with food to improve absorption and reduce any potential GI discomfort. Splitting it into morning and evening doses works well, especially if you're using it for both recovery and sleep. I generally recommend magnesium glycinate for most clients—it's well-absorbed, calming without being sedating, and easy on the gut, making it a reliable choice for long-term use.
The Bottom Line
Magnesium isn’t just a nice bonus—it’s one of those behind-the-scenes essentials your body relies on for steady energy, good sleep, balanced hormones, and handling stress. The frustrating part is that you can subjectively feel off even if your labs say everything looks fine.
Smart Strategies for Magnesium Optimization:
Start with food: Prioritize leafy greens, nuts, seeds, legumes, and dark chocolate. Food should always be your foundation.
Know what you're taking: Look for the elemental magnesium dose on supplements—not just total compound weight.
Pick the right form: Glycinate is my go-to for most clients—especially those dealing with stress, poor sleep, or gut sensitivity.
Split your dose: Morning + evening dosing (with food) tends to boost absorption and avoids GI issues.
Test smarter: If symptoms persist despite "normal" labs, ask for RBC magnesium or ionized magnesium—not just serum levels.
Adjust based on demand: Training hard? Under a lot of stress? Sweating a lot? You likely need more than the RDA.
Coach’s Perspective
Most people I work with feel noticeably better within 2–4 weeks of repleting magnesium—especially when it comes to sleep, recovery, and mood stability. It’s one of the lowest-hanging pieces of the performance puzzle, and one that often gets overlooked until it's already causing problems.
References:
Veronese et al., 2021
Maggio et al., 2011
Brilla & Conte, 2000
Zogović et al., 2014
Wienecke & Nolden, 2016
Abbasi et al., 2012
Golf et al., 2018
Lukaski, 2001
What Else I’m Reading
“A clinical study on the effect of nattokinase on carotid artery atherosclerosis and hyperlipidaemia” — Ren et al. (2017, Zhonghua Yi Xue Za Zhi)
In this 6-month study, nattokinase (6,000 FU/day) reduced carotid artery plaque by 36%—more than triple the reduction seen with simvastatin (11%). Both treatments improved cholesterol, but only nattokinase raised HDL (“good” cholesterol). And the plaque benefits didn’t fully line up with cholesterol changes, suggesting nattokinase may help through other pathways like improving blood flow or breaking down clots.
📌 Takeaway: Nattokinase outperformed a statin at shrinking artery plaque in this small trial. It may offer vascular benefits beyond cholesterol lowering—but it’s not a replacement for statins if you need strong LDL control.
“Polyphenol‑Rich Sorghum bicolor Extract Enhances Strength Recovery After Eccentric Exercise” — Mitchinson et al. (2025, J Strength Cond Res)
In this study, men took either a high or low dose of Sorghum bicolor extract (rich in polyphenols) or a placebo for 18 days. After a muscle-damaging workout, both supplement groups recovered strength faster than placebo—especially the high dose, which showed improvements by 48 hours. There was no difference in soreness or swelling.
📌 Takeaway: A polyphenol-rich sorghum supplement helped speed up strength recovery after tough workouts—without changing how sore people felt.
“Effects of Moderate-Intensity Resistance Training on Vascular Function in Healthy Young Men” — Zhang et al. (2024, J Strength Cond Res)
In this 12-week study, healthy young men trained with moderate weights (65% of 1RM) three times per week. By the end, they showed improved vascular function—specifically better flow-mediated dilation, a marker of artery health—without changes in blood pressure or resting heart rate.
📌 Takeaway: Regular, moderate-weight strength training can improve blood vessel health, even in already healthy young adults. Another win for lifting that doesn’t require maxing out.
Before you go 💬
I started writing because I kept having conversations that didn’t quite fit into a session or an Instagram post. If you’re thinking through something—training, nutrition, mindset, whatever—or just want to share what’s been working for you, hit reply. I read everything, and I’m always open to talking through it. And if someone in your life could benefit from this approach—feel free to share it. The more people thinking clearly about performance and health, the better.