NOW Magnesium Citrate 200 mg Tablets Review
#1 of 5 · Best overall for constipation✓ Label verified · Supplement Facts read Oct 14, 2026Real retailer photo, cut out. Label unedited.
Consider it. The cheap, flexible citrate: one tablet for daily use, two when you need to go. Magnesium citrate absorbs better than oxide (Walker 2003) and still pulls enough water into the gut to soften stool.
$19.99 · 250 tablets (Amazon US, Oct 14, 2026)$0.08 per 200 mg tablet
Why It Scores 7.8 — And The Label Line Behind Each Number
Form bioavailability
30% of scoreMagnesium citrate. In Walker 2003, citrate raised blood and urine magnesium more than oxide and an amino acid chelate over 60 days. It also draws water into the bowel at higher doses, which is why it works for constipation and why glycinate is the gentler choice for sleep.
- Form
- Magnesium citrate tablets
- Other ingredients
- Hydroxypropyl cellulose, microcrystalline cellulose, vegetarian coating, stearic acid, croscarmellose sodium, magnesium stearate
Elemental Mg per serving
25% of score200 mg of magnesium per tablet and 400 mg per two-tablet serving, as printed on the panel. Easy to split: one tablet stays under the 350 mg upper limit for supplemental magnesium, two go above it.
- Per serving
- 400 mg magnesium (2 tablets, from 2,667 mg magnesium citrate)
Lab transparency
20% of scoreNOW tests its products in its own laboratories and the label carries the GMP Quality Assured seal. No product-level seal from NSF or USP.
- Testing
- NOW in-house testing, GMP Quality Assured seal; no NSF or USP listing
Cost per active mg
15% of score$19.99 for 250 tablets on Oct 14, 2026: 8 cents per 200 mg tablet, about 4 cents per 100 mg of magnesium. The cheapest citrate on this list per milligram.
- Per tablet
- 200 mg magnesium
- Servings
- 125 per bottle (250 tablets)
- Price
- $19.99 for 250 tablets (Amazon US, Oct 14, 2026)
- Cost per 200 mg tablet
- $0.08
Real-world response
10% of scoreWorks reliably as a gentle osmotic laxative at one to two tablets. Some people get cramping or urgency at two tablets on an empty stomach; taking it with food and water helps.
Label verified. Every figure read from the Supplement Facts photo, Oct 14, 2026.
Marketing Claims Vs. Reality
Nervous system support.
Magnesium is needed for normal nerve function, so correcting a low intake helps. There is no evidence that extra magnesium improves nerve function in people who already get enough.
Supports energy production.
True as biology: magnesium is a cofactor in energy metabolism. It does not mean you will feel more energetic unless you were low.
A fully reacted mineral supplement.
The panel lists magnesium citrate as the source, 2,667 mg for 400 mg of magnesium, which matches the magnesium content of the citrate salt.
What Our Test Actually Found
One tablet or two is the real choice
The label serving is two tablets, 400 mg. That is above the 350 mg upper limit for magnesium from supplements, a limit set because of diarrhea. For constipation that effect is wanted; for everyday use one tablet with a meal is enough.
Citrate sits between oxide and glycinate
Citrate absorbs better than oxide (Walker 2003) but leaves more magnesium in the gut than glycinate. That middle position makes it the usual pick when you want a softer stool without the harsher effect of oxide.
Cheaper than the powder drinks
Natural Vitality Calm gives a similar citrate dose as a flavored drink for several times the price per milligram. If you do not need the drink, these tablets do the same job.
Full analysis: all pros & cons (7), buy if / skip if
- 200 mg of magnesium per tablet, easy to adjust
- Plain citrate, no sweeteners or flavors
- About 8 cents per tablet
- Vegetarian and vegan
- Two-tablet serving is above the 350 mg supplement limit
- Tablets are large
- No NSF or USP seal
- You want magnesium citrate for occasional constipation and like to adjust the dose
- You want the lowest price per milligram for citrate
- You prefer tablets to a powder drink
- You want magnesium for sleep or calm without loose stools: glycinate is gentler
- You have kidney disease: talk to your doctor before any magnesium
- You struggle with large tablets
Magnesium citrate absorbs better than oxide (Walker 2003) and still pulls enough water into the gut to soften stool. NOW sells it as a plain 200 mg tablet for about 8 cents each. The printed serving of two tablets is more than most people need every day.
Magnesium citrate is the form people reach for when they are constipated, and this is the plainest way to buy it. Each tablet holds 200 mg of magnesium from citrate; the label serving is two tablets, 400 mg, made from 2,667 mg of magnesium citrate. The other ingredients are fillers and a coating, nothing else. It is cheap and flexible, because you can take one tablet or two. The one thing to know: two tablets go above 350 mg, the upper limit for magnesium from supplements, and loose stools are the usual result. For constipation that is the point; for daily use one tablet is the safer amount.
The best value if you want citrate
For occasional constipation, start with one tablet in the evening with a full glass of water and go to two if nothing happens by the next day. For daily magnesium without loose stools, take one tablet or choose a glycinate instead. Talk to a doctor first if you have kidney disease or take antibiotics, bisphosphonates or thyroid medication, because magnesium can interfere with them.
If This Doesn’t Fit — Try These
02Natural Vitality CALM
If you prefer a drink to tablets, start here.
03Pure Magnesium Citrate
Choose it if fillers bother you or you want to raise the dose in small steps: one capsule in the evening, one more each day until it works.
05Nature Made Mg Oxide
It scores lowest because it is a poor way to raise your magnesium level.
Quick Answers
How many NOW magnesium citrate tablets should I take for constipation?
Start with one tablet (200 mg) in the evening with a full glass of water. If nothing happens by the next day, two tablets is the label serving. Do not keep taking more; see a doctor if constipation lasts.
Is 400 mg of magnesium citrate too much?
It is above the 350 mg upper limit for magnesium from supplements, which is set because of diarrhea. For short-term constipation relief that is expected. For daily use, one tablet is the safer amount.
Magnesium citrate or glycinate?
Citrate if you want a softer stool, glycinate if you want magnesium for sleep or calm without effects on the bowel.
Is NOW magnesium citrate third-party tested?
NOW tests in its own laboratories and carries a GMP seal. The product is not listed with NSF or USP.
Sources & Further Reading
1 peer-reviewed source, each linked to PubMed
- [1] Walker 2003 PMID 14596323 — Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. 46 healthy adults took 300 mg of magnesium a day as citrate, amino acid chelate or oxide for 60 days. Citrate gave the highest blood magnesium after a single dose and after 60 days; oxide did not differ from placebo.
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