Medical Disclaimer: Magnesium supplements are generally safe. Contraindicated in severe renal impairment (eGFR <30). May interact with antibiotics (quinolones, tetracyclines), bisphosphonates, diuretics, PPIs. Consult a healthcare provider if you have kidney disease, heart block, or are on medications.
Key Takeaways
- Form determines function. Glycinate = sleep/relaxation. Threonate = cognitive. Citrate = constipation. Malate = energy. Taurate = cardiac. Oxide = avoid (poor absorption).
- Elemental magnesium matters. Labels list compound weight (e.g., 500mg magnesium glycinate = ~50mg elemental). Dose by elemental.
- Target: 200–400mg elemental/day for sleep/relaxation. Higher for deficiency (under medical supervision).
- RBC magnesium > serum. Serum = 1% of total; RBC reflects tissue status. Target 6.0–6.5 mg/dL.
- Food first: Pumpkin seeds (156mg/oz), spinach (157mg/cup cooked), black beans (120mg/cup), dark chocolate 85% (64mg/oz).
Magnesium Forms Compared
| Form | Elemental Mg% | Absorption | Primary Use | Best For | Avoid If |
|---|---|---|---|---|---|
| Glycinate / Bisglycinate | 14% | High (chelated, amino acid transport) | Sleep, anxiety, muscle relaxation | Insomnia, stress, sensitive GI | — |
| Threonate (Magtein®) | 7% | High (crosses BBB) | Cognitive, memory, neuroprotection | Brain health, aging, students | Budget (expensive) |
| Citrate | 16% | Good (organic acid) | Constipation, kidney stone prevention | Occasional constipation | Chronic use (loose stool) |
| Malate | 15% | Good | Energy, fibromyalgia, muscle pain | Chronic fatigue, fibro | — |
| Taurate | 9% | Good | Cardiac, blood pressure, insulin sensitivity | Hypertension, metabolic health | — |
| Orotate | 7% | Good | Cardiac, athletic performance | Heart failure, athletes | Cost |
| L-Threonate | 7% | High (BBB) | Cognitive, sleep architecture | Memory, learning, sleep quality | Cost |
| Oxide | 60% | Very poor (<4%) | Laxative only | Severe constipation (short-term) | Any other purpose |
| Chloride | 12% | Good (topical) | Topical (oil, lotion, bath) | GI intolerance, local muscle | — |
| Sulfate (Epsom Salt) | 10% | Topical only | Bath soak (transdermal debated) | Relaxation ritual | Oral (bitter, laxative) |
Dosing by Goal
| Goal | Form | Elemental Dose | Compound Dose (approx) | Timing |
|---|---|---|---|---|
| Sleep onset / quality | Glycinate | 200–400mg | 1400–2800mg glycinate | 1–2h pre-bed |
| Anxiety / stress | Glycinate | 200–400mg | 1400–2800mg glycinate | Split AM/PM |
| Cognitive / memory | Threonate (Magtein®) | 144mg (2g Magtein®) | 2g Magtein® | AM + PM |
| Constipation | Citrate | 200–400mg | 1250–2500mg citrate | With meals |
| Muscle cramps / recovery | Glycinate or Malate | 200–400mg | 1400–2800mg | Post-workout / PM |
| Blood pressure / heart | Taurate or Orotate | 200–400mg | 2200–4400mg | Split AM/PM |
| General maintenance | Glycinate | 200–300mg | 1400–2100mg glycinate | With dinner |
| Deficiency correction | Glycinate + Citrate | 400–800mg (MD supervised) | Split doses | With meals |
Magnesium + Cofactors (Synergy)
- Vitamin D3: Mg required for D3 → 25(OH)D → 1,25(OH)2D conversion. Low Mg = D3 supplementation ineffective.
- Vitamin K2 (MK-7): Mg + D3 + K2 = calcium into bones, not arteries.
- Boron: 3mg/day ↑ Mg retention, ↑ D3, ↑ testosterone.
- B6 (P5P): Mg + B6 = GABA synthesis, ↓ anxiety (synergistic).
- Taurine: Mg + taurine = cardiac electrophysiology, insulin sensitivity.
Testing: Know Your Status
| Test | What It Measures | Optimal Range | Utility |
|---|---|---|---|
| RBC Magnesium | Intracellular Mg (99% of total) | 6.0–6.5 mg/dL | Gold standard for tissue status |
| Serum Magnesium | Extracellular (1% of total) | 1.8–2.4 mg/dL | Poor; normal until severe depletion |
| Ionized Magnesium | Free, biologically active | 0.5–0.65 mmol/L | Best but rarely available |
| 24h Urinary Mg | Excretion (reflects intake/absorption) | 40–120 mg/24h | Research; not routine |
Rule: If serum Mg is low, you’re severely depleted. If serum is normal, you may still be depleted (check RBC).
Brand Comparison (Tested, Glycinate Focus)
| Brand | Form | Elemental Mg/Serving | Cost/Serving | Testing | Notes |
|---|---|---|---|---|---|
| Thorne | Bisglycinate | 200mg (2 caps) | $0.25 | NSF Sport | Clinical grade, no buffer |
| Pure Encapsulations | Glycinate | 120mg (1 cap) | $0.18 | NSF, USP | Hypoallergenic, no magnesium stearate |
| Doctor’s Best | Bisglycinate (Albion®) | 200mg (2 tabs) | $0.08 | ConsumerLab | Best value, Albion chelate |
| Jigsaw Health | MagSRT (Dimagnesium Malate + B6) | 500mg (4 tabs, SRT) | $0.30 | ConsumerLab | Sustained release, B6 synergy |
| Life Extension | Neuro-Mag (Magtein® Threonate) | 144mg (3 caps) | $0.60 | ConsumerLab | Only for cognitive; expensive |
| Natural Vitality | Calm (Citrate powder) | 325mg (2 tsp) | $0.15 | ConsumerLab | Fizzy drink, good for constipation |
| KAL | Glycinate | 200mg (2 tabs) | $0.06 | ConsumerLab | Budget option |
Side Effects & Management
- Diarrhea (most common): → Reduce dose, switch to glycinate, split doses, take with food.
- Nausea: → Take with food, reduce dose.
- Low blood pressure / dizziness: → Reduce dose, split AM/PM, monitor if on antihypertensives.
- Muscle weakness (rare, high dose): → Stop, check renal function.
Drug Interactions (Critical)
| Drug Class | Interaction | Management |
|---|---|---|
| Quinolone antibiotics (cipro, levo) | Mg chelates → ↓ antibiotic absorption | Separate by 4–6h |
| Tetracycline antibiotics (doxy) | Mg chelates → ↓ absorption | Separate by 4–6h |
| Bisphosphonates (alendronate) | Mg chelates → ↓ absorption | Separate by 2h |
| Diuretics (loop/thiazide) | ↑ Mg excretion → deficiency risk | Monitor RBC Mg; supplement often needed |
| PPIs (omeprazole, pantoprazole) | ↓ Mg absorption (acid-dependent) | Monitor; glycinate less affected |
| ACE inhibitors / ARBs | ↑ K+ retention; Mg sparing | Monitor K+; usually beneficial |
Frequently Asked Questions
Can I get enough magnesium from food?
Possible but difficult. RDA: 400mg men, 310mg women. Top sources: pumpkin seeds (156mg/oz), chia (111mg/oz), almonds (80mg/oz), spinach (157mg/cup cooked), black beans (120mg/cup). Soil depletion + processing = lower food Mg. Most adults benefit from 200mg supplemental.
Why does magnesium citrate make me poop but glycinate doesn’t?
Citrate draws water into colon (osmotic laxative) + stimulates peristalsis. Glycinate is absorbed via amino acid transporters in small intestine — minimal colonic arrival. Choose citrate FOR constipation, glycinate FOR sleep/relaxation.
Is magnesium threonate worth the cost?
Only if: cognitive enhancement is primary goal AND budget allows. For sleep/anxiety/general: glycinate 400mg = threonate 2g (144mg elemental) at 1/4 the cost. Threonate’s BBB crossing is unique but clinical outcome data limited.
Can I take magnesium with my multivitamin?
Most multis have 50–100mg Mg oxide (poorly absorbed). Take dedicated Mg supplement separately. If multi has glycinate/citrate at 100mg+, you may not need extra for maintenance.
References
- Barbagallo M, Dominguez LJ. “Magnesium and Type 2 Diabetes.” World J Diabetes. 2015;6(13):1152-1159.
- Abbasi B, et al. “Magnesium Supplementation for Insomnia.” J Res Med Sci. 2012;17(12):1161-1169.
- Slutsky I, et al. “Enhancement of Learning and Memory by Elevating Brain Magnesium.” Neuron. 2010;65(2):165-177.
- Rosique-Esteban N, et al. “Magnesium and Cardiovascular Disease.” Nutrients. 2018;10(12):1984.
- Kass L, et al. “Magnesium Supplementation and Blood Pressure.” J Clin Hypertens. 2012;14(7):441-448.
