Creatine vs Magnesium: Which Supplement Should You Take After 40?

Here's the honest answer upfront: this isn't really an either/or decision. Magnesium is an essential mineral that most adults aren't getting enough of. Creatine is one of the most well-studied performance and aging supplements in existence. They do different things, they work through different mechanisms, and for adults over 40, there's a strong case for taking both.

But "take both" isn't particularly useful advice unless you understand why. So let's break down what each one actually does, what the human evidence shows, where the costs land, and how to think about prioritizing if your budget forces a choice.

How Magnesium Works: The Essential Mineral You're Probably Missing

Think of magnesium as your body's backstage crew. It's involved in over 300 enzymatic reactions in the human body. It's not a supplement in the way most people think of supplements — it's a nutrient your body requires for basic operations: muscle contraction, nerve signaling, protein synthesis, blood sugar regulation, blood pressure control, bone mineralization, DNA repair, and energy production (ATP itself is biologically active only when bound to magnesium). Without magnesium, your cellular machinery doesn't just slow down. It stalls.

The problem? Most Americans aren't getting enough. Not even close. According to a 2012 analysis by Rosanoff, Weaver, and Rude published in Nutrition Reviews, an estimated 50 to 80 percent of Americans consume less magnesium than the recommended daily allowance. This isn't a fringe estimate. The National Health and Nutrition Examination Survey (NHANES) data consistently shows that average dietary magnesium intake falls below the RDA across nearly every age group over 30.

Why the shortfall? Modern food processing strips magnesium from grains. Soil depletion has reduced magnesium content in produce over the past century. Diets heavy in processed foods naturally contain less of it. And certain common factors accelerate magnesium loss: stress, alcohol consumption, some prescription medications (particularly proton pump inhibitors and diuretics), and — here's the cruel part — aging itself. After 40, intestinal magnesium absorption decreases while urinary excretion increases. Your body needs more at exactly the age when it gets less. Biology has a dark sense of humor.

This isn't a trendy deficiency. It's a widespread, well-documented nutritional gap with real consequences.

How Creatine Works: Cellular Energy on Demand

Creatine is a naturally occurring compound your body synthesizes from three amino acids (arginine, glycine, and methionine), primarily in the liver and kidneys. You also get creatine from dietary sources like red meat and fish, though amounts vary.

Its function is specific, elegant, and well understood. Creatine is stored in cells as phosphocreatine. When a cell burns ATP for energy and produces ADP, phosphocreatine donates its phosphate group back to ADP, rapidly regenerating ATP. Think of it like a rechargeable battery that tops itself off in seconds. It's the fastest energy recycling system in the human body. Your muscles rely on it during high-intensity contractions. Your brain relies on it during periods of cognitive demand.

After 40, this system starts to lose its edge. Your body's own creatine production declines. If you eat less red meat (as many adults do for cardiovascular or ethical reasons), dietary intake drops further. Total creatine stores shrink alongside declining muscle mass. The result? Less available cellular energy at a time when your tissues are already under age-related stress. Not ideal.

Creatine supplementation directly replenishes those stores. With over 700 peer-reviewed human studies behind it, creatine monohydrate is one of the most thoroughly validated supplements available. We're not talking about a promising extract from some obscure berry. We're talking about decades of rigorous science saying the same thing: this works. For a full exploration of how this relates to the aging process, see our guide on creatine for longevity.

The Human Evidence: What Each Supplement Actually Does for Adults Over 40

Both creatine and magnesium have substantial human research behind them. But the types of evidence, and the claims they support, are quite different. Let's dig in.

Magnesium's Evidence Base

Magnesium research spans decades and covers a wide range of health outcomes. The evidence is strongest in the following areas:

Sleep quality. If you're lying awake at 2 AM wondering why you can't sleep, low magnesium might literally be part of the answer. A 2012 randomized controlled trial by Abbasi et al., published in the Journal of Research in Medical Sciences, found that magnesium supplementation (500 mg daily) significantly improved sleep quality, sleep time, and sleep efficiency in elderly subjects with insomnia. Participants also showed reduced serum cortisol levels — meaning they were less physiologically stressed. A 2023 systematic review and meta-analysis by Arab et al. in BMC Complementary Medicine and Therapies confirmed that magnesium supplementation is associated with improvements in subjective sleep quality, particularly in adults with low baseline magnesium levels.

Muscle cramps. Magnesium deficiency is a well-established contributor to muscle cramps, particularly those lovely nocturnal leg cramps that become more common after 40. While the evidence for magnesium treating cramps in the general population is mixed (Garrison et al., 2012, Cochrane Database of Systematic Reviews), the benefit appears clearer in populations with documented magnesium insufficiency — which, as we've established, includes the majority of American adults. If your calf wakes you up feeling like it's trying to escape your leg, magnesium is worth a shot.

Blood pressure. A 2016 meta-analysis by Zhang et al., published in Hypertension (an American Heart Association journal), analyzed 34 randomized controlled trials totaling over 2,000 participants. They found that magnesium supplementation at a median dose of 368 mg per day significantly reduced both systolic and diastolic blood pressure. The effect was modest (roughly 2 mmHg systolic, 1.8 mmHg diastolic) but consistent across studies. Not going to replace your medication, but a nice tailwind in the right direction.

Bone health. Magnesium plays a direct role in bone mineralization. Roughly 60 percent of your body's magnesium is stored in bone tissue — it's not just passing through. Ryder et al. (2005) found that higher magnesium intake was associated with greater bone mineral density in older white men and women in the Framingham cohort. Low magnesium has also been linked to increased osteoclast activity (the cells that break down bone) and decreased osteoblast activity (the cells that build bone), creating a net loss in bone density over time. Basically, low magnesium tips the scales toward demolition.

Migraine prevention. The American Academy of Neurology and the American Headache Society recognize magnesium as a "probably effective" preventive treatment for migraine. A 1996 trial by Peikert et al. in Cephalalgia found that 600 mg of magnesium daily reduced migraine frequency by 41.6 percent compared to 15.8 percent in the placebo group. For anyone who's suffered through migraines, that's a meaningful difference for a cheap mineral.

Creatine's Evidence Base

Creatine's human research base is enormous — bordering on absurd for a supplement. The International Society of Sports Nutrition (ISSN) position stand, published by Kreider et al. in 2017, reviewed the totality of evidence and drew several firm conclusions:

Muscle preservation and strength. Multiple meta-analyses confirm that creatine supplementation combined with resistance training increases lean mass and muscular strength in older adults. Chilibeck et al. (2017, Open Access Journal of Sports Medicine) found that creatine augmented the effects of resistance training on lean tissue mass and upper body strength in adults over 50. For adults over 40, where sarcopenia (age-related muscle loss) accelerates at roughly 1 to 2 percent per year, this has direct functional significance. We're talking about the difference between carrying your own groceries at 70 and not. Our article on creatine after 40 covers this in detail.

Cognitive function. Here's where creatine gets really interesting. It's not just a muscle supplement. Your brain consumes roughly 20 percent of your body's total energy despite making up only 2 percent of body weight — it's the most expensive organ you own, metabolically speaking. Rae et al. (2003, Proceedings of the Royal Society B) demonstrated that creatine supplementation improved working memory and processing speed. Avgerinos et al. (2018, Experimental Gerontology) conducted a systematic review concluding that creatine supplementation improves short-term memory and reasoning, particularly under conditions of stress or sleep deprivation. So yes, creatine is brain food. Literally.

Bone density. Creatine has shown promise for supporting bone mineral density, especially when paired with resistance exercise. Chilibeck et al. (2015) found that creatine plus resistance training preserved bone mineral density in postmenopausal women more effectively than resistance training alone. For a deeper look, see our article on creatine and bone density.

Cellular energy. The fundamental mechanism (ATP regeneration via the phosphocreatine shuttle) supports tissue function across the entire body. This broad energy support is why creatine's benefits show up in so many different outcome measures — from muscle and brain to bone. It's not doing one thing well. It's doing one thing that matters everywhere.

Creatine vs Magnesium: Side-by-Side Comparison

Cost Comparison: Two of the Most Affordable Supplements Available

One of the best things about both creatine and magnesium? Neither will make your wallet cry. Compared to compounds like NMN ($60-120 per month), resveratrol, or CoQ10, both creatine and magnesium are remarkably cost-effective.

Creatine monohydrate costs roughly $0.30 to $0.50 per day at the standard 5-gram dose. That's $10 to $15 per month. Magnesium supplements range from $0.20 to $0.60 per day depending on the form, putting monthly costs at $6 to $18. Combined, you're looking at roughly $16 to $33 per month for both.

Over a five-year period (a reasonable supplementation horizon for someone serious about long-term health), the combined cost of creatine and magnesium totals roughly $960 to $1,980. For context, a single month of some premium longevity supplements exceeds the annual cost of both creatine and magnesium together. Let that sink in.

This cost accessibility is part of the reason the "take both" answer actually works in practice. You're not choosing between a $15 supplement and a $100 one. You're choosing between two supplements that each cost less than a daily coffee. Skip the oat milk latte twice a week and you've covered both.

Safety: What the Research Shows About Long-Term Use

Creatine Safety

Creatine monohydrate has one of the strongest safety records of any dietary supplement. Full stop. The ISSN position stand (Kreider et al., 2017) concluded that creatine at recommended doses is safe for healthy individuals, including with long-term use up to five years. A 2021 review by Antonio et al. in the Journal of the International Society of Sports Nutrition systematically addressed common misconceptions, confirming that creatine does not damage kidneys or liver in healthy adults, does not cause dehydration, and does not increase injury risk. If someone tells you otherwise, they're working off gym folklore, not science.

The only consistently reported side effect is mild water retention during the first week or two of use, which is transient and harmless. In older adults specifically, multiple trials have reported no significant adverse events. For details on safety considerations for older populations, see our article on creatine after 40.

Magnesium Safety

Magnesium from food sources carries essentially no toxicity risk. Supplemental magnesium is also very safe at standard doses (200-400 mg of elemental magnesium per day), though the tolerable upper intake level set by the Institute of Medicine for supplemental magnesium is 350 mg per day for adults.

The most common side effect of magnesium supplementation is gastrointestinal discomfort — primarily loose stools or diarrhea. This is more likely with certain forms (magnesium oxide and magnesium citrate have stronger laxative effects) and at higher doses. Magnesium glycinate and magnesium threonate tend to be gentler on the gut.

People with kidney disease should use caution, as impaired kidneys can't excrete excess magnesium efficiently. For everyone else, supplemental magnesium at standard doses is well tolerated and has decades of safety data behind it.

Both supplements have strong enough safety profiles that long-term daily use is well supported by the existing literature. These aren't experimental compounds — they're staples.

Can You Take Creatine and Magnesium Together?

Yes. And honestly, the combination makes more physiological sense than taking either one alone.

Here's why: ATP, the energy currency your cells run on, is biologically active only when bound to a magnesium ion. Creatine's entire mechanism revolves around regenerating ATP via the phosphocreatine shuttle. If your magnesium levels are low, your ATP can't function optimally regardless of how much creatine you take. It's like putting premium fuel in a car with a broken spark plug. Adequate magnesium is essentially a prerequisite for creatine to do its job fully.

There are no known negative interactions between creatine and magnesium. They can be taken at the same time or at different times of day. Some people prefer to take magnesium in the evening (particularly magnesium glycinate, which has calming properties that may support sleep) and creatine in the morning or around training. Do whatever you'll actually stick with.

A practical daily protocol:

• Creatine monohydrate: 3-5 grams daily, mixed in water. No loading phase is necessary. Consistency matters more than timing. See our creatine dosage guide for full details.
• Magnesium glycinate or citrate: 200-400 mg of elemental magnesium daily. Start at the lower end and increase if tolerated. Evening dosing may benefit sleep.

This combination covers two of the most common nutritional gaps in adults over 40 (low creatine stores and magnesium insufficiency) at a combined cost of roughly $20 per month. That's less than most people spend on streaming services they don't watch.

Who Should Prioritize Creatine? Who Should Prioritize Magnesium?

If you can only start with one (due to budget, simplicity, or personal preference), here's how to think about it:

Start with magnesium if you:

• Experience frequent muscle cramps, especially at night
• Have trouble sleeping or staying asleep
• Deal with chronic stress (which depletes magnesium faster)
• Take medications known to reduce magnesium levels (PPIs, diuretics, certain antibiotics)
• Have been told you have borderline high blood pressure
• Suffer from migraines
• Eat a diet heavy in processed foods and low in leafy greens, nuts, and seeds

Start with creatine if you:

• Are concerned about age-related muscle loss or declining strength
• Want to support cognitive function and mental sharpness as you age
• Are active and want to get more out of your resistance training
• Follow a plant-based or low-meat diet (and have lower baseline creatine stores)
• Want to support bone mineral density alongside exercise
• Are looking for the single most evidence-backed performance and aging supplement available

The best case scenario:

Take both. They're affordable, safe, well-studied, and address different but complementary aspects of aging. If you think of your supplement routine as a foundation rather than a collection of experiments, creatine and magnesium are two of the strongest building blocks you can start with. For a broader framework on supplement prioritization, see our guide to the best supplements for aging.

Frequently Asked Questions

Is magnesium or creatine better for muscle cramps?

Magnesium wins this one. Muscle cramps, particularly nocturnal leg cramps, are frequently associated with magnesium insufficiency. Creatine can help indirectly by improving overall muscle function and hydration status, but if cramps are your primary concern, correcting a likely magnesium deficit should be your first move.

Can creatine and magnesium be taken at the same time of day?

Yes. There are no absorption conflicts or interactions between the two. Some people prefer to split them (creatine in the morning, magnesium in the evening) because certain magnesium forms have calming effects that may aid sleep. But taking them together is perfectly fine — your body won't be confused.

What form of magnesium is best for adults over 40?

Magnesium glycinate is widely considered the best-tolerated form with good bioavailability and minimal GI side effects. Magnesium citrate is also well absorbed but has a mild laxative effect at higher doses (plan accordingly). Magnesium threonate (branded as Magtein) has some evidence for crossing the blood-brain barrier more effectively and may offer cognitive benefits, though the research is still limited. Avoid magnesium oxide for supplementation purposes — its absorption rate is significantly lower (roughly 4 percent compared to 20-30 percent for glycinate and citrate). You'd basically be paying to not absorb magnesium.

How do I know if I'm magnesium deficient?

Here's the frustrating part: standard blood tests (serum magnesium) aren't very reliable for detecting insufficiency because only about 1 percent of your body's magnesium is in the blood. Serum levels can appear normal even when tissue stores are depleted. Red blood cell (RBC) magnesium is a somewhat better marker. Given that the majority of adults eating a typical Western diet are likely insufficient, many clinicians recommend magnesium supplementation as a reasonable default rather than waiting for a confirmed deficiency. It's cheap, it's safe, and the odds are you need it.

Does creatine cause weight gain?

Creatine can cause a small increase in body weight (typically 1 to 3 pounds) during the first one to two weeks of supplementation. Before you panic — this is water retention in muscle cells, not fat gain. It's actually a sign that creatine is working (it draws water into muscle tissue as part of the cell volumization process). After the initial phase, any additional weight gain is typically lean mass, which is exactly what you want if you're over 40 and fighting age-related muscle loss. This is the good kind of weight gain.

Can I get enough creatine and magnesium from food alone?

In theory, yes. In practice, good luck. To get 5 grams of creatine from food, you'd need to eat roughly 2.5 pounds of raw beef or 3 pounds of salmon daily. Every day. Forever. For magnesium, the RDA for adult men is 420 mg and for women 320 mg. Reaching that through food requires consistent intake of magnesium-rich foods like pumpkin seeds, almonds, spinach, black beans, and dark chocolate. Most adults fall short. Supplementation fills the gap affordably and reliably — and nobody has to eat three pounds of salmon.

How long does it take for creatine and magnesium to work?

Creatine saturates muscle and brain tissue within 2 to 4 weeks of consistent daily supplementation at 3 to 5 grams per day. Some cognitive benefits have been observed in studies as short as six weeks. Magnesium's effects on sleep and muscle cramps can often be noticed within one to two weeks. Blood pressure effects typically become measurable after four to eight weeks of consistent use. Neither is an instant fix, but both reward patience.

The Bottom Line

This comparison doesn't produce a single winner because these supplements serve fundamentally different roles. Magnesium is a mineral your body requires for basic biochemistry, and the majority of adults aren't getting enough of it. Creatine is a performance and aging compound with one of the strongest research portfolios in all of nutritional science. Comparing them is like asking whether you need a foundation or a roof. You need both.

The practical answer for most adults over 40 is simple: take both. They cost roughly the same as a daily coffee combined. They're both safe with decades of research behind them. They work through completely different mechanisms (magnesium as an essential mineral cofactor, creatine as an ATP regeneration system). And they address some of the most common age-related concerns: declining energy, weakening muscles, thinning bones, poor sleep, and cognitive slowdown.

If you're building a supplement foundation rather than chasing the latest trend, creatine monohydrate and magnesium belong at the base.

If you're looking for a high-quality creatine monohydrate designed specifically for adults focused on long-term health, AgeWell Creatine is third-party tested, unflavored, and built for daily longevity use.

References

1. Rosanoff, A., Weaver, C.M., & Rude, R.K. (2012). Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews, 70(3), 153-164. doi:10.1111/j.1753-4887.2011.00465.x

2. Abbasi, B., Kimiagar, M., Sadeghniiat, K., Shirazi, M.M., Hedayati, M., & Rashidkhani, B. (2012). The effect of magnesium supplementation on primary insomnia in elderly: A double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences, 17(12), 1161-1169.

3. Zhang, X., Li, Y., Del Gobbo, L.C., et al. (2016). Effects of magnesium supplementation on blood pressure: a meta-analysis of randomized double-blind placebo-controlled trials. Hypertension, 68(2), 324-333. doi:10.1161/HYPERTENSIONAHA.116.07664

4. Kreider, R.B., Kalman, D.S., Antonio, J., et al. (2017). International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine. Journal of the International Society of Sports Nutrition, 14(18). doi:10.1186/s12970-017-0173-z

5. Chilibeck, P.D., Kaviani, M., Candow, D.G., & Zello, G.A. (2017). Effect of creatine supplementation during resistance training on lean tissue mass and muscular strength in older adults: a meta-analysis. Open Access Journal of Sports Medicine, 8, 213-226. doi:10.2147/OAJSM.S123529

6. Rae, C., Digney, A.L., McEwan, S.R., & Bates, T.C. (2003). Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial. Proceedings of the Royal Society B: Biological Sciences, 270(1529), 2147-2150. doi:10.1098/rspb.2003.2492

7. Avgerinos, K.I., Spyrou, N., Bougioukas, K.I., Kapogiannis, D., Bagos, P.G., & Karanicolas, P.J. (2018). Effects of creatine supplementation on cognitive function of healthy individuals: A systematic review of randomized controlled trials. Experimental Gerontology, 108, 166-173. doi:10.1016/j.exger.2018.04.013

8. Peikert, A., Wilimzig, C., & Kohne-Volland, R. (1996). Prophylaxis of migraine with oral magnesium: results from a prospective, multi-center, placebo-controlled and double-blind randomized study. Cephalalgia, 16(4), 257-263. doi:10.1046/j.1468-2982.1996.1604257.x

9. Ryder, K.M., Shorr, R.I., Bush, A.J., et al. (2005). Magnesium intake from food and supplements is associated with bone mineral density in healthy older white subjects. Journal of the American Geriatrics Society, 53(11), 1875-1880. doi:10.1111/j.1532-5415.2005.53561.x

10. Antonio, J., Candow, D.G., Forbes, S.C., et al. (2021). Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show? Journal of the International Society of Sports Nutrition, 18(1), 13. doi:10.1186/s12970-021-00412-w

11. Garrison, S.R., Allan, G.M., Sekhon, R.K., Musini, V.M., & Khan, K.M. (2012). Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews, (9). doi:10.1002/14651858.CD009402.pub2

12. Arab, A., Rafie, N., Amani, R., & Shirani, F. (2023). The role of magnesium in sleep health: a systematic review of available literature. BMC Complementary Medicine and Therapies, 23(1), 24. doi:10.1186/s12906-022-03839-z

13. Chilibeck, P.D., Candow, D.G., Landeryou, T., Kaviani, M., & Paus-Jenssen, L. (2015). Effects of creatine and resistance training on bone health in postmenopausal women. Medicine and Science in Sports and Exercise, 47(8), 1587-1595. doi:10.1249/MSS.0000000000000571

Disclaimer: These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. The information provided in this article is for educational purposes only and should not be considered medical advice. Consult your healthcare provider before starting any new supplement regimen.