Magnesium Supplement Label Audit: Serving Size and Real Cost

What changes when you read the whole serving

Across these eight products, the labeled elemental magnesium amount runs from 144 to 400 mg per serving. That serving can mean one scoop, two tablets, two capsules, three capsules, or four capsules. A bottle with more pieces does not necessarily contain more servings.

Solaray's 120-capsule glycinate bottle provides 30 four-capsule servings. NOW's 180-tablet bottle provides 90 two-tablet servings. Those are three times as many labeled servings, even though the bottle counts differ by only 60 pieces. This comparison says nothing about which dose is appropriate for you.

The biggest number on a label can also refer to the magnesium compound. Life Extension Neuro-Mag lists 2,000 mg of magnesium L-threonate complex but 144 mg of elemental magnesium. Doctor's Best similarly identifies a 2,000 mg chelate source while declaring 200 mg of magnesium. We use the declared magnesium amount, not the complex weight, in every calculation.

The eight-product label comparison

These are specified U.S. versions, not every size or reformulation sold under the same product name. The price table below uses only rows with a matched pack and a dated price.

For the underlying form differences, see our magnesium form guide. This audit adds product-level serving counts and calculations; it is not a new ranking of the best magnesium form.

What the price actually buys

A price per capsule is useful only if the capsules contain comparable amounts. Price per labeled serving answers a different question: how much does one full Supplement Facts serving cost? Our normalized cost per 100 mg compares quantities, not absorption or clinical benefit.

All prices are one-time U.S. dollar snapshots before tax and shipping. The NOW price was recorded on October 7, 2026; the other included prices were checked on October 9. Subscription discounts, coupons, bundles, and different sellers can change the result. Blank prices mean we did not establish a reliable pack-matched price, not that the product is unavailable.

Reproduce the calculation

Cost per serving = bottle price / labeled servings. Cost per 100 mg = bottle price / (servings x elemental magnesium per serving / 100). We calculate with full precision and round only the displayed results to the nearest cent.

For the 240-tablet Doctor's Best pack, $23.99 / 120 servings = approximately $0.20 per serving. Its 200 mg serving costs approximately $0.10 per 100 mg. The denominator is 120 labeled servings, not 240 tablets and not the number of days suggested by the manufacturer's full daily directions.

For the 90-capsule Neuro-Mag pack, $31.50 / 30 servings = $1.05 per serving. Dividing that by 1.44 gives approximately $0.73 per 100 mg of elemental magnesium. The higher normalized cost does not establish that a different form is better for your reason for taking magnesium.

Where a cheap comparison becomes misleading

• Serving is not a prescription. We have not recommended taking a full labeled serving, increasing a dose, or splitting a product to reach a calculated target.
• Powder scoop weights vary. Thorne has separate 187 g and 226.2 g records. This dataset uses the 187 g version and its 3.11 g scoop, not the other pack's 3.77 g scoop.
• A lower cost does not measure tolerability. Diarrhea and other digestive effects are not captured by price arithmetic.
• Certification has a scope. A named product directory listing is different from a manufacturer's facility certification or an ingredient trademark. None is a percentage effectiveness rating.

NIH sets the adult upper limit for magnesium from supplements and medications at 350 mg per day, unless a clinician advises otherwise; magnesium naturally present in food is treated separately. The 400 mg citrate serving in this table is a label fact, not an instruction to exceed that limit. Kidney disease and medicines such as certain antibiotics or bisphosphonates need an individual safety check. See magnesium interactions before choosing a product.

Read the product details before buying

If the serving count or ingredient list rules out a product for you, the fuller reviews explain its format and tradeoffs. Product reviews may contain affiliate links; how those links work.

Thorne Magnesium Bisglycinate

Magnesium Bisglycinate · reviewed 187 g powder

Read the product review

Doctor's Best High Absorption Magnesium

High Absorption Magnesium · 240 tablets

Read the product review

Solaray Magnesium Glycinate Powder

Magnesium Glycinate Powder · 9.8 oz

Read the product review

Methods, data and reuse

This is a convenience sample of eight products already covered on Supplement Explained, selected to include several brands, forms, and serving formats with identifiable labels. It is not a random sample, sales ranking, laboratory analysis, or comprehensive survey of U.S. magnesium supplements.

We rechecked manufacturer pages and available label information on October 9, 2026, and retained explicitly identified version details from our October 7 label records. NOW's label is sourced from its matched HerbsPro listing. Source dates, exact packs, missing prices, and version notes are retained in the CSV. Product claims are not independently tested by us.

Price selection is independent of whether a seller pays an affiliate commission. The Solaray glycinate page contains inconsistent structured price/variant entries, so its capsule price is deliberately excluded. Thorne's changing pack size also prevents us from assigning its current page price to the older 187 g pack.

You may reuse our original comparison table and calculations with attribution and a link to this page under CC BY 4.0. Manufacturer wording, trademarks, and product photographs remain their owners' material. Please retain the dates and limitations rather than calling these live prices.

Sources

1. https://www.thorne.com/products/dp/magnesium-bisglycinate
2. https://www.herbspro.com/products/magnesium-glycinate-5
3. https://www.doctorsbest.com/products/doctor-s-best-high-absorption-magnesium-lysinate-glycinate-chelated-albion-traacs-240-tablets-100-mg-per-tablet-16567
4. https://solaray.com/products/magnesium-glycinate
5. https://www.naturemade.com/products/high-absorption-magnesium-glycinate-200-mg-capsules
6. https://www.lifeextension.com/vitamins-supplements/item01603/neuro-mag-magnesium-l-threonate
7. https://solaray.com/products/magnesium-glycinate-powder
8. https://solaray.com/products/magnesium-citrate
9. https://ods.od.nih.gov/factsheets/Magnesium-HealthProfessional/

Source access and version dates are recorded in the CSV. Research process / Editorial policy