Example of Magnesium supplement containing different forms and also some vitamin B6 (no affiliation)

Here is what I learned on Magnesium and how I apply that knowledge to myself. I am not a doctor. Not medical advice. Double check everything with your own research.

Why Magnesium is important

Therefore, a deficiency in Magnesium can lead to many problems, many of them building up slowly (you don’t get osteopenia from one day to the next). At the very least, without enough Mg, your body functions sub-optimally with consequences like:

  • Waking up at night and having trouble falling back to sleep
  • General fatigue; low energy
  • Mood issues
  • Faster heart rate
  • Heart arrhythmia
  • Numbness / tingling in fingers & toes

Signs you may be deficient

Many symptoms like fatigue or insomnia (see “Why Mg is important” above) are not specific to magnesium but the following should make you consider magnesium carefully:

  • Muscle cramps and twitches (pretty common!)
  • Low bone density (which you may have found on a DXA scan)

Natural sources

Roughly ordered from most potent to less potent:

  • Chia Seeds
  • Nuts
    • Brazil nuts have most BUT beware of too much Selenium
    • Cashews
    • Almonds
  • Leafy Greens (chlorophyl which contains Mg)
    • Spinach
  • Pumpkin seeds
  • Dark Chocolate (take one without the sugar)
  • Black beans
  • Avocado

Unfortunately, traditional agriculture has depleted the soils to a point that minerals that used to be abundant in the food are no longer in there, at least not at the same levels.

Also milk and dairy (H. Eustina Oh 2017), which is also dependent on what the cows ate.

Furthermore, it is estimated that 25 to 75% of the Mg in food will be absorbed. In plants, the Mg may be wrapped in fiber that makes it less available than Mg in animal products.

Lab tests

  • Overall, magnesium is hard to measure reliably!
    • The true buffer is in the bone (60% of the global body Mg store), which is basically impossible to measure.
  • Serum Mg level (approx 2€) is not a good indicator because only 1% of the total body Mg is in the blood serum.
    • The body maintains the blood in homeostasis (take from the bone to maintain the blood) and serum levels will generally be in the normal range even for people who are severely depleted.
  • Red Blood Cell (RBC) Magnesium (Erythrocyte Magnesium) (approx 2 €) measures the Mg in the red blood cells. This accounts for approx 40% of total body Mg.
    • Here again, the body will take from the bone to build the cells with the Mg they need.
    • However, you can see if you err at the bottom of the normal range, which is some sort of an indication.
    • RBCs regenerate over 3 months. So the result is an indication of average Mg availability over the last 3 months
    • Consequently, it also requires to wait 3 months for the RBCs to regenerate in order to see the effect when starting supplementation
    • My theory: it’s even worse than waiting for 3 months: if your bones are depleted, RBC levels may not rise for several years because all the new Mg will go to replete the bones first.
  • Urinary test (approx 2 €): collect all urine over a period of 24 hours and look at how much Mg is excreted this way over a day:
    • Less Mg in Urine means you are probably deficient because kidneys have “not much excess to evacuate”
      • Kidneys normally do evac about 100 mg/day (and the intestines: 20 mg/day)
      • The way kidneys function is that they throw everything out of the blood and then reabsorb what they need. They typically can’t reabsorb 100%. This is why there is alway some loss through urine, even when severely depleted.
    • Check normal values
    • Advanced variation: Magnesium Loading Test: You inject a fixed dosed of magnesium and check how much you urinate out.
    • There are also “one shot” urinary tests which may be useful to see when, in the day, you excrete more in regards to when you supplement.

Supplementation

❗ Kidney health

Kidneys regulate Magnesium in the body:

  • If you have good functioning kidneys, it’s not a big issue to supplement a bit too much. Kidneys will evacuate the excess.
  • In case of compromised kidney healt, it is very IMPORTANT NOT TO over-supplement.

Since Magnesium is a metal, you need to combine it with something else before you can use it as a supplement.

Pay attention to look at the milligrams of the magnesium inside the supplement molecule and not at the total weight of the supplement.

  • The minimum you want would be around 400 mg/day absorbed, coming from food + supplements. But remember a large part will not be absorbed and another large part will be excreted.
  • Several doctors recommend 600 to 800 mg/day if you have functioning kidneys and reason to believe you are deficient (eg: Dr Peter Attia)
  • Some people need all the way up to 2400 mg/day to get rid of their cramps! (I would no go this high without medical supervision)
  • The first sign of too much Mg supplementation is often fast transit.
  • There are many different forms of Magnesium. Some are much better absorbed than others.
  • You can’t necessarily trust the labels of the supplements (maybe the contain only 70% of what the label says)

Caveats:

  • Spread the dose across the day for better absorption and also to prevent competition with calcium absorption (probably only a concern if supplementing in calcium and not a concern with dietary calcium)
  • Check Vitamin D interaction

Magnesium Supplement Price Comparison

Product Daily Qty (caps) Daily Dose (mg of Mg) Active/cap (mg) Caps Container Total mg Price Price per 400 mg Price per cap Price per day
ErgyMag 180 Caps 4 forms incl unspecified qty of Mg Oxide :/ + Zn, B1, B2, B3, B5, B6, B8 3 300 100.0 180 18 000 €25.39 €       0.564 €       0.141 €       0.423
Pure Encaps Magnesium citrate 90 caps 2 300 150.0 90 13 500 €25.99 €       0.770 €       0.289 €       0.578
Fitoform Magnesium Marin +B1,B6,B9 1 300 300.0 30 9 000 €19.12 €       0.850 €       0.637 €       0.637
Be Life Mg Quatro (3 forms) 900 180 Caps 4 356 89.0 180 16 020 €38.15 €       0.953 €       0.212 €       0.848
Be Life Mg Quatro (3 forms) 900 60 Caps 4 356 89.0 60 5 340 €16.92 €       1.267 €       0.282 €       1.128
Lepivits Magnesium Malate 60 Gel 2 115 57.5 60 3 450 €12.95 €       1.501 €       0.216 €       0.432
Intelligent Labs MagEnhance (partially Magtein) Magnesium L Threonate Komplex 3 200 66.7 90 6 000 €28.87 €       1.925 €       0.321 €       0.962
Strong Natural - Magnesium L-Threonate 120 Capsules (Not Magtein licensed) 4 176 44.0 120 5 280 €35.13 €       2.661 €       0.293 €       1.171
Apollo’s Hegemony Magtein® Magnesium L-Threonate 3 144 48.0 90 4 320 €37.90 €       3.509 €       0.421 €       1.263
Vit4ever Magtein 4 150 37.5 120 4 500 €4.99 €       3.999 €       0.375 €       1.500
MoleQlar Magnesium L-Threonate Capsules Pack of 90 3 150 50.0 90 4 500 €45.00 €       4.000 €       0.500 €       1.500
Life Extension, Neuro-Mag Magnesium L-Threonate Minerals 90 Capsules 3 144 48.0 90 4 320 €57.02 €       5.280 €       0.634 €       1.901
SuperSmart Magnesium L-Threonate (Magtein) 4 144 36.0 120 4 320 €67.15 €       6.218 €       0.560 €       2.238
I-like-it-Clean® Magtein® Powder 7 200 € 71.62 €       3.979

More info

My experience

  • Baseline RBC test: 1.7 mmol/L which is at the low end
  • I started supplementing end of Jan 2025 with 356mg/day (Be Life Quattro)
  • New RBC test mid march: 1.6 mmol/L ! :/
    • Maybe not significative (error margin of the test).
    • Otherwise, how can it go down if I supplement?
    • Maybe interaction with something else?
    • No matter what, I should wait 3 months for RBCs to fully regenerate before drawing conclusions, but early indication is that there’s probably not more Mg available for RB C cells to use.
    • Might increase the dose, but do 24H urinary test first
  • 24H urinary test first: excreting just shy of 200 mg/day.
    • This would indicate adequate supplementation. If going way over 200 mg/day it would even indicate excessive supplementation.
    • I need to test again, once with higher supplementation, and once with cutting supplementation completely to establish a baseline.
      • Not sure of how many days to wait between dose change and new measure…

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