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Home › Minerals › Magnesium

Magnesium Oxide

Also called mag, mg glycinate, mag glycinate and 8 more

magnesium bisglycinate, magnesium citrate, magnesium malate, magnesium taurate, magnesium threonate, magtein, magnesium oxide, magnesium chloride.

Cheapest magnesium oxide: 4p per 100 mg magnesium at Boots, of 9 products at 4 shops. Price checked 15 October 2026.

The best price per 100 mg magnesium and per month across 4 UK retailers, and where to buy it cheapest. A unit for comparing, not advice.

Email me when it gets cheaper ↓

Comparing magnesium

We count the magnesium a label states per serving, whatever the pack size or the serving size, so every product sits on one scale. Magnesium comes as bisglycinate (glycinate), citrate, malate, taurate, L-threonate, oxide, chloride, and blends and other forms, and each form has its own table, because someone buying one would not usually take another as a like-for-like substitute. A product with one other ingredient is ranked here with an “also contains” note; products that combine magnesium with several others are listed separately, because their price buys more than magnesium. 100 mg is our unit for comparing prices, not a dose to take: the label’s directions and a pharmacist decide that.

Newest prices checked: ; an older price shows its own date. Ranked purely by price per 100 mg magnesium — a comparison unit, not a recommendation. We earn commission when you buy through these links; it never affects the order.

2 of the 9 cheapest links on this page earn us nothing; the order is price alone. Shop by shop

Priced per 100 mg; powders are often compared per gram.

Compared at 100 mg. Enter the amount you take to see your own costs.

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Magnesium Oxide: products ranked by price per 100 mg magnesium
RankProductPer 100 mg magnesiumPer monthLastsBuyHow it is worked out
1
Cheapest per doseMagnesium 375mg 180 Tablets (3 month supply)180 tablets · 90 servings · 375 mg a servingDetails and price historyAdd to my stack
4p£1.1411 months£12.85View at Boots (opens in a new tab)Price checked Free delivery over £25.00, otherwise £3.95AmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 180 ÷ 2 per serving = 90
  • In the pack: 90 × 375 mg = 33.8 g
  • £12.85 ÷ 33.8 g × 100 mg = 3.81p per 100 mg
  • Amount per serving: stated on the label.
What the retailer's listing says
  • pack units “180 Tablets”
  • units per serving “Take 2 tablets a day”
  • amount per serving “Magnesium 375mg 100”

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2
Best value under 6 months' supplyMagnesium 375mg 60 Tablets (1 Month Supply)60 tablets · 30 servings · 375 mg a servingDetails and price historyAdd to my stack
5p£1.414 months£5.30View at Boots (opens in a new tab)Price checked Free delivery over £25.00, otherwise £3.95AmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 60 ÷ 2 per serving = 30
  • In the pack: 30 × 375 mg = 11.3 g
  • £5.30 ÷ 11.3 g × 100 mg = 4.71p per 100 mg
  • Amount per serving: stated on the label.
What the retailer's listing says
  • pack units “60 Tablets”
  • units per serving “Take 2 tablets a day”
  • amount per serving “Magnesium 375mg”

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3
Magnesium Tablets 200mg360 tablets · 360 servings · 100 mg a servingDetails and price historyAdd to my stack
5p£1.6112 months£19.29View at Simply Supplements (opens in a new tab)Free delivery from £20.00, otherwise £1.99 · 2–3 working days after dispatchAmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 360 ÷ 1 per serving = 360
  • In the pack: 360 × 100 mg = 36 g
  • £19.29 ÷ 36 g × 100 mg = 5.36p per 100 mg
  • Amount per serving: stated on the label.
What the retailer's listing says
  • amount per serving “provides 100mg of bioavailable magnesium”
  • compound mass “Each of our magnesium tablets contains 167mg of magnesium oxide”
  • confirmed values “confirmed from the retailer's own product page, not this listing's text: pack units 360; pack unit type tablet; units per serving 1.0”

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4
Essential Magnesium TabletsMyprotein · 270 tablets · 90 servings · 300 mg a servingDetails and price historyAdd to my stackclaimed: vegan
5p£1.619 months£14.49View at Myprotein (opens in a new tab)Free delivery over £55.00, otherwise £4.49 · 2–3 working daysAmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 270 ÷ 3 per serving = 90
  • In the pack: 90 × 300 mg = 27 g
  • £14.49 ÷ 27 g × 100 mg = 5.37p per 100 mg
  • Amount per serving: stated on the label.
What the retailer's listing says
  • pack units “270 Tablets”
  • units per serving “Consume 3 tablets daily”
  • amount per serving “Magnesium ; 300mg ; 80”

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5
Essential Magnesium TabletsMyprotein · 90 tablets · 30 servings · 300 mg a servingDetails and price historyAdd to my stackclaimed: vegan
6p£1.833 months£5.49View at Myprotein (opens in a new tab)Free delivery over £55.00, otherwise £4.49 · 2–3 working daysAmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 90 ÷ 3 per serving = 30
  • In the pack: 30 × 300 mg = 9 g
  • £5.49 ÷ 9 g × 100 mg = 6.1p per 100 mg
  • Amount per serving: stated on the label.
What the retailer's listing says
  • pack units “90 Tablets”
  • units per serving “Consume 3 tablets daily”
  • amount per serving “Magnesium ; 300mg ; 80”

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6
Mag O7 Oxygen Detox Cleanse - PowderHealf · 150 g · 60 servings · 1.04 g a servingDetails and price historyAdd to my stackalso contains potassium
8p£2.271.7 years£46.99View at Healf (opens in a new tab)Free UK delivery over £50.00, otherwise £3.99AmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 150 ÷ 2.5 per serving = 60
  • In the pack: 60 × 1.04 g = 62.1 g
  • £46.99 ÷ 62.1 g × 100 mg = 7.57p per 100 mg
  • Amount per serving: stated on the label.
  • Also contains: potassium. The price counts the magnesium only.
What the retailer's listing says
  • pack units “150g”
  • servings stated “Servings Per Container: 60”
  • units per serving “Serving Size: 1/2 Teaspoon (2.5g)”
  • amount per serving “(as Ozonated Magnesium Oxides) ; 1035 mg”

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7
Mag O7 Oxygen Detox CleanseHealf · 180 capsules · 60 servings · 1.04 g a servingDetails and price historyAdd to my stackalso contains potassium
8p£2.411.7 years£49.99View at Healf (opens in a new tab)Free UK delivery over £50.00, otherwise £3.99AmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 180 ÷ 3 per serving = 60
  • In the pack: 60 × 1.04 g = 62.1 g
  • £49.99 ÷ 62.1 g × 100 mg = 8.05p per 100 mg
  • Amount per serving: stated on the label.
  • Also contains: potassium. The price counts the magnesium only.
What the retailer's listing says
  • pack units “180 caps”
  • units per serving “Serving Size: 3 Capsules”
  • amount per serving “(as Ozonated Magnesium Oxides) ; 1035 mg”

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8
Mag O7 Oxygen Detox CleanseHealf · 90 capsules · 30 servings · 1.04 g a servingDetails and price historyAdd to my stackalso contains potassium
11p£3.3810 months£34.99View at Healf (opens in a new tab)Free UK delivery over £50.00, otherwise £3.99AmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 90 ÷ 3 per serving = 30
  • In the pack: 30 × 1.04 g = 31.1 g
  • £34.99 ÷ 31.1 g × 100 mg = 11.3p per 100 mg
  • Amount per serving: stated on the label.
  • Also contains: potassium. The price counts the magnesium only.
What the retailer's listing says
  • pack units “90 caps”
  • units per serving “Serving Size: 3 Capsules”
  • amount per serving “(as Ozonated Magnesium Oxides) ; 1035 mg”

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9
Mag O7 Oxygen Detox CleanseHealf · 30 capsules · 10 servings · 1.04 g a servingDetails and price historyAdd to my stackalso contains potassium
23p£6.953 months£23.99View at Healf (opens in a new tab)Free UK delivery over £50.00, otherwise £3.99AmazonFind it on Amazon (opens in a new tab)A search, not a matched product. Price not compared.
Show the working
  • Servings: 30 ÷ 3 per serving = 10
  • In the pack: 10 × 1.04 g = 10.4 g
  • £23.99 ÷ 10.4 g × 100 mg = 23.2p per 100 mg
  • Amount per serving: stated on the label.
  • Also contains: potassium. The price counts the magnesium only.
What the retailer's listing says
  • pack units “30 caps”
  • servings stated “Servings Per Container: 10”
  • units per serving “Serving Size: 3 Capsules”
  • amount per serving “(as Ozonated Magnesium Oxides) ; 1035 mg”

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By shop

Each shop's magnesium products, with where its cheapest sits in the market.

How we work out these prices

We count the elemental magnesium a product provides, not the weight of the whole compound it comes in. If a label states the magnesium amount, we use it. If it only gives the compound's weight, we estimate using a published conversion factor and mark the figure “estimated”. If we cannot tell which the number means, the product is left out until it can be confirmed.

Conversion factor used when only the compound weight is given: oxide 60.3%. How we chose these.

Our full method · All magnesium forms