A single-marker blood test that measures your serum magnesium level, suited to anyone who wants to check this one mineral rather than a full panel.
1 biomarker as listed by Forth.
Magnesium is a mineral involved in muscle and nerve function and in maintaining a normal heart rhythm. This test measures serum magnesium only, so it gives a single reading rather than a broader nutritional picture. It suits anyone who has been advised to check this specific marker, for example if you get muscle cramps or have symptoms a GP has linked to magnesium.
Against the other magnesium tests we track, Forth's version sits at the lower end of the price range: £45 compares with £45.25 from Blue Horizon Medicals for the same single serum marker, £55 from Medichecks, and £136.25 for Blue Horizon's whole blood magnesium test, which measures a different, more complete form of the mineral. If you specifically want the whole blood measurement rather than serum, none of Forth's magnesium tests cover that.
The score here is driven mostly by convenience and price. Collection scores highly because you can use a finger-prick kit, Forth's AutoDraw device, a home nurse visit, or a venous draw at a partner clinic, and results are back in 2 days. Clinical depth is rated as adequate rather than high, because a single-marker test is not designed to be comprehensive; that reflects what this comparison group covers rather than a shortcoming.
This suits you if you want a quick, low-cost check of your serum magnesium level, for example to monitor levels alongside symptoms like muscle cramps or fatigue, without paying for a wider panel. If you would rather measure whole blood magnesium instead of serum, Blue Horizon Medicals offers a Whole Blood Magnesium test, though at £136.25 it costs substantially more.
You can collect your sample with an at-home finger-prick kit, Forth's AutoDraw device, during a home nurse visit, or via a venous draw at a partner clinic. The sample is sent to Forth's lab for analysis, and a doctor reviews your result before it is released. Results are typically available within 2 days of the lab receiving your sample.
At £45, this single-marker serum magnesium test is the cheapest of the four magnesium tests we compare and sits just under the group median of £50.13. It can be done entirely at home and comes with a doctor review of your result within 2 days. Because it checks only one marker, it will not tell you much beyond your magnesium status.
The listing publishes a short description, the full biomarker list, a stated turnaround, clear collection options, the sample type; it does not state what the report looks like.
A single-marker test measuring exactly what it sets out to; depth is not the point of this comparison group.
A finger-prick sample you take at home; a home nurse visit is offered; results in around 2 days, in line with or faster than similar tests.
Results are reviewed by a doctor; the provider does not describe the report format.
Trustpilot 4.2 from 1,727 reviews; accredited lab (UKAS ISO 15189 partner labs); doctor review as standard; trading 10+ years.
£45.00 against a comparison-group median of £50.13 (-10%).
Calculated 13 September 2026 from the facts we hold about this test and provider, using our published scoring formula. Scores are not hand-edited.
This test belongs to our Magnesium test comparison group. See how it stacks up against equivalent tests from other providers.
Closely matches the cheapest magnesium test on the market
Checks serum magnesium levels, a mineral linked to fatigue, muscle cramps and weakness when low.
Pricier than two peers, cheaper than whole-blood option
Measures serum magnesium, a mineral involved in muscle function, nerve signalling and heart health. Suited to people with fatigue, cramps or low energy who want to check whether low magnesium could be a factor.
Priciest magnesium test in this group by some margin
This is a single blood test for magnesium, measured in whole blood rather than serum, which can give a more complete picture of the body's total magnesium level. It suits people who want the whole blood method specifically, rather than the more common serum test.
Closely matches the cheapest magnesium test on the market
Checks serum magnesium levels, a mineral linked to fatigue, muscle cramps and weakness when low.
Pricier than two peers, cheaper than whole-blood option
Measures serum magnesium, a mineral involved in muscle function, nerve signalling and heart health. Suited to people with fatigue, cramps or low energy who want to check whether low magnesium could be a factor.
Priciest magnesium test in this group by some margin
This is a single blood test for magnesium, measured in whole blood rather than serum, which can give a more complete picture of the body's total magnesium level. It suits people who want the whole blood method specifically, rather than the more common serum test.
