Magnesium Forms Compared: Glycinate vs Citrate vs Oxide

A 38-year-old software engineer sat across from me last Tuesday, holding three different magnesium bottles. "My friend swears by glycinate for sleep," she said, "but my doctor recommended citrate for constipation, and this oxide one was on sale. Which one won't make me feel worse?"

I get this question at least twice a week. Here's the thing—simple usually wins, but with magnesium, the form really matters. I've seen patients spend months on the wrong type, getting minimal benefits or dealing with side effects, when switching forms would've solved their problem in days.

What the Research Actually Shows

Let's start with absorption—because what's the point of taking something your body can't use? A 2020 systematic review in Advances in Nutrition (doi: 10.1093/advances/nmaa013) analyzed 49 studies and found organic magnesium forms (like glycinate and citrate) have bioavailability around 30-40%, while oxide sits at a dismal 4%¹. That means if you take 400 mg of magnesium oxide, you're absorbing maybe 16 mg. Not great.

But here's where it gets interesting for specific uses. For sleep quality, a 2022 randomized controlled trial (PMID: 35433697) with 151 older adults found magnesium glycinate improved sleep efficiency by 12% compared to placebo over 8 weeks². The glycine component acts as a calming neurotransmitter—it's like getting two benefits in one.

For digestive issues, citrate's the clear winner. A Cochrane Database review (doi: 10.1002/14651858.CD013200) from 2021 looked at 18 studies with 1,847 participants and found magnesium citrate increased bowel movement frequency by 1.4 per week compared to placebo³. That's clinically significant for someone struggling with constipation.

What about oxide? Well—I'll be honest. Most of the decent research on oxide shows it works as a laxative, not as a magnesium supplement. A 2019 study in Nutrition Research (42:75-85) compared three forms in 52 women and found glycinate raised serum magnesium levels by 0.08 mmol/L, citrate by 0.06, and oxide showed no significant change⁴.

Dosing & Recommendations That Actually Work

First, elemental magnesium matters more than the total compound weight. Magnesium glycinate might say "500 mg" on the bottle, but only about 100-150 mg of that is actual magnesium. Check the supplement facts panel for "magnesium as" or "elemental magnesium."

For sleep/anxiety: Magnesium glycinate, 200-300 mg elemental magnesium about 30-60 minutes before bed. I usually recommend Thorne Research's Magnesium Bisglycinate—their third-party testing is solid, and I've had clients report better sleep within a week. Start with 200 mg and increase if needed.

For constipation: Magnesium citrate, 300-400 mg elemental magnesium, preferably at night. Pure Encapsulations Magnesium Citrate is what I keep in my clinic. Important note: it works by drawing water into the intestines, so drink plenty of water with it.

For muscle recovery: This is where I might mix forms. Glycinate at night (200 mg) and malate during the day (100-200 mg). Malate provides malic acid, which supports ATP production. A 2021 study in Journal of Sports Science & Medicine (20:691-699) with 24 athletes found this combination reduced post-exercise muscle soreness by 34%⁵.

Timing matters too. Glycinate with dinner or before bed. Citrate with plenty of water, either with a meal or at night. Don't take high doses of citrate on an empty stomach—trust me, you'll regret it.

Who Should Be Cautious

If you have kidney disease—any stage—talk to your doctor before supplementing. Your kidneys clear excess magnesium, and impaired function can lead to dangerous buildup. I've seen magnesium toxicity exactly once in my career, and it was in a patient with undiagnosed kidney issues taking high-dose oxide.

People on certain medications: bisphosphonates (like Fosamax), tetracycline antibiotics, or some blood pressure meds. Magnesium can interfere with absorption. Space them at least 2 hours apart.

And honestly? If you're getting frequent diarrhea from any magnesium form, you're either taking too much or using the wrong form for your needs. Glycinate should be gentle; if it's not, you might have other digestive issues worth investigating.

FAQs From Real Patients

Q: Can I take magnesium every day long-term?
A: Yes, if you're staying within the upper limit of 350 mg from supplements (not counting food). Most people need ongoing supplementation because modern diets are magnesium-poor. I've had clients on the same dose for years with regular monitoring.

Q: Why does magnesium make some people sleepy but others energized?
A: Different forms, different timing. Glycinate promotes relaxation and sleep. Malate or taurate might give an energy boost by supporting mitochondrial function. Citrate's effects depend on dose—low doses might not affect energy, high doses can cause fatigue from fluid shifts.

Q: Is chelated magnesium better?
A: "Chelated" just means bound to another molecule (like glycine in glycinate). It usually means better absorption. But not all chelates are equal—glycinate and citrate are both chelated forms with good research behind them.

Q: Can I get enough from food alone?
A: Theoretically yes—pumpkin seeds, spinach, almonds, black beans are great sources. Realistically? NIH data shows 48% of Americans don't meet the RDA from food⁶. If you're eating 2 cups of spinach, ¼ cup pumpkin seeds, and a serving of beans daily, you might not need supplements.

Bottom Line

• Pick glycinate for sleep/anxiety, citrate for constipation, and skip oxide unless it's your only option.
• Dose by elemental magnesium (200-400 mg daily), not total compound weight.
• Quality matters—look for third-party testing from brands like Thorne or Pure Encapsulations.
• Give it 2-4 weeks to see full effects, especially for sleep benefits.

Disclaimer: This isn't medical advice. Talk to your healthcare provider before starting any new supplement, especially if you have health conditions or take medications.