The Best Magnesium L-Threonate
The best magnesium L-threonate is Double Wood, at $1.00 a day. It gives 2,000 mg of Magtein, the brand of magnesium L-threonate used in the trials, and it is on NSF/ANSI 173, so an outside lab checks the label. People take it for memory, focus and sleep.
By Erin Rose Updated November 2, 2026 How we score
Our pick for: Memory, focus or sleep
- Per day
- $1.004 capsules: 2,000 mg Magtein, 144 mg magnesium
- A bottle
- $29.95120 capsules, 30 days, on Amazon
- Testing list
- NSF/ANSI 173Checks the label and contaminants
Why we pick it It holds the full 2,000 mg of Magtein a day, and NSF lists Double Wood Magnesium L-Threonate on NSF/ANSI 173. That program checks that what the label says is in the bottle and that metals stay within limits. NSF's listing covers every version of Double Wood's magnesium L-threonate. It names 8 capsules, the label's most per day; the usual dose is 4. It also costs the least a day of the four here.
What you give up It takes 4 capsules a day, not 3. NSF/ANSI 173 does not screen for drugs banned in sport. If you are tested, Momentous is.
The best magnesium L-threonate for your needs
Double Wood suits most people. If you are tested for drugs in sport, or want 3 capsules a day, pick one of these.
Drug-tested in sport: Momentous
Momentous gives 2,000 mg of Magtein in 3 capsules and is on NSF Certified for Sport, which also screens for drugs banned in sport. It costs 67 cents a day more than Double Wood. Check your bottle's lot on NSF's listing.
Momentous
$1.67 a day · $49.99 a bottle (90 capsules, 30 days)
Three capsules a day: Life Extension Neuro-Mag
Life Extension Neuro-Mag gives the same 2,000 mg of Magtein in 3 capsules, for 3 cents a day more than Double Wood. It is not on a testing list.
Life Extension Neuro-Mag
$1.03 a day · $30.78 a bottle (90 capsules, 30 days)
What magnesium L-threonate is
Magnesium L-threonate is magnesium bound to threonate, a compound your body makes when it breaks down vitamin C. Magtein is the brand name of the version used in the human trials. Each 2,000 mg of it holds about 144 mg of magnesium.
That is far less magnesium than most adults need in a day (310 to 420 mg, counting food). For more magnesium for less money, see the best magnesium glycinate or L-threonate vs glycinate.
What the trials found
In a 6-week trial of 100 adults aged 18 to 45 who slept poorly, 2 g of Magtein a day beat a placebo on an overall thinking test score and on reaction time. It improved one self-rated sleep score, but not sleep measured by a sleep-tracking ring or most other sleep scores.
In a 3-week trial of adults with sleep problems, 1 g a day led to higher deep and REM sleep scores on a sleep-tracking ring, and better ratings of mood and energy, than a placebo.
In a 12-week trial of 44 adults aged 50 to 70 with memory and thinking problems, a magnesium L-threonate product beat a placebo on a combined thinking score.
All three trials are small, and a company selling magnesium L-threonate ran or paid for each.
How to choose magnesium L-threonate
Check for 2,000 mg a day
That is the dose in the 100-person trial. It gives about 144 mg of magnesium.
Compare the cost of a day
Bottles hold different capsule counts, so compare one day's dose. The table does the math.
4 magnesium L-threonate capsules compared
Cheapest per day first, at Amazon prices checked November 6, 2026. Amazon prices change, so the order can too.
| Capsule | Cost per day | Why it is or is not the pick |
|---|---|---|
| Double WoodNSF/ANSI 173 · 4 capsules | $1.00 | Our pick: NSF/ANSI 173, lowest cost a day |
| NOW MagteinNo testing list · 3 capsules | $1.00 | Same dose in 3 capsules; not on a testing list |
| Life Extension Neuro-MagNo testing list · 3 capsules | $1.03 | Same dose in 3 capsules; not on a testing list |
| MomentousNSF Certified for Sport · 3 capsules | $1.67 | Screens for banned drugs too |
Questions people ask
Does magnesium L-threonate help you sleep?
Maybe. In a 3-week trial, adults with sleep problems who took 1 g a day had higher deep and REM sleep scores on a sleep-tracking ring than those on a placebo. In a 6-week trial of 100 adults, 2 g a day improved one self-rated sleep score, but not sleep measured by the ring. Companies that sell magnesium L-threonate funded or ran both trials.
Can I take it with magnesium glycinate?
Yes, if the total stays at or under 350 mg of magnesium a day from supplements, the NIH upper limit for adults. A day of Magtein gives about 144 mg, so that leaves room for about 206 mg more.
Is it safe?
The trials reported it as well tolerated. If you have kidney disease, ask your doctor before you take magnesium. Weak kidneys cannot clear the extra, so it can build up (NIH).
Can I take it with antibiotics?
Yes, but space them out: take tetracyclines (such as doxycycline) or quinolones (such as ciprofloxacin) at least 2 hours before or 4 to 6 hours after magnesium (NIH).
How we picked
We looked for magnesium L-threonate capsules sold on Amazon that give 2,000 mg of Magtein a day. We checked each against NSF/ANSI 173, NSF Certified for Sport, Informed Choice and USP. With the dose the same, we ranked on a testing list first, then the cost of a day. See all forms of magnesium compared, the best magnesium overall and the magnesium guide.
Sources
- Amazon listings for Double Wood, Momentous, Life Extension Neuro-Mag and NOW Magtein magnesium L-threonate, read November 2, 2026.
- NSF/ANSI 173 company listing for Double Wood LLC (Magnesium L-Threonate, all product IDs), read November 2, 2026: info.nsf.org. NSF Certified for Sport listing for Momentous Magnesium Threonate: nsfsport.com.
- NIH Dietary Supplement Label Database, Double Wood Magnesium L-Threonate 2000 mg, label 286153 (4 capsules a day, 8 at most): dsld.od.nih.gov.
- NIH Dietary Supplement Label Database, Neuro-Mag Magnesium L-Threonate (Life Extension), label 328600: dsld.od.nih.gov. 144 mg magnesium per 3 capsules.
- Lopresti AL, et al. The effects of magnesium L-threonate (Magtein®) on cognitive performance and sleep quality in adults: a randomised, double-blind, placebo-controlled trial. Front Nutr. 2025.
- Hausenblas HA, et al. Magnesium-L-threonate improves sleep quality and daytime functioning in adults with self-reported sleep problems. Sleep Med X. 2024.
- Liu G, et al. Efficacy and safety of MMFS-01, a synapse density enhancer, for treating cognitive impairment in older adults. J Alzheimers Dis. 2016.
- NIH Office of Dietary Supplements. Magnesium fact sheet for health professionals (daily needs, upper limit, kidney disease, antibiotics).