Can You Take Thiamine With Magnesium?

Quick answer

NIH's thiamin and magnesium fact sheets do not mention each other, and we found no trial of the pair in healthy people. In laboratory work, enzymes that use thiamin need magnesium to function. Thiamin has no upper limit, while magnesium from supplements has an adult limit of 350 mg a day.^1,2,3

Key facts

Thiamin becomes thiamin diphosphate, a cofactor that five enzymes need to break down sugars, amino acids and fats.¹
Human transketolase, a thiamin-dependent enzyme, holds one magnesium beside its thiamin cofactor at each of two active sites, and in laboratory tests it bound the cofactor only when magnesium was present.³
In rat liver, the enzyme that makes thiamin diphosphate from thiamin was activated by magnesium ions.⁴
Above about 5 mg a day the gut absorbs a smaller share of thiamin, and the share of magnesium absorbed also falls as the amount taken rises.^1,5
Thiamin has no upper limit, while supplemental magnesium is limited to 350 mg a day for adults.^1,2

What the sources say about this pair

Neither NIH fact sheet mentions the other nutrient, so the usual consumer sources are silent on this pair. The link that does exist is biochemical. It comes from laboratory studies of enzymes and from one small hospital study that used injections, not from trials of the two supplements in healthy adults.^1,2,3,6

That shapes what this page can honestly offer. It cannot promise a benefit from taking both. It can show where the two meet in the body, how their amounts and absorption compare, and who should ask a professional before combining them.

Where magnesium turns up in thiamin chemistry

Thiamin works mainly after the body converts it to thiamin diphosphate, which NIH calls its main metabolically active form. In rat liver, the enzyme that attaches phosphate groups to thiamin to make thiamin diphosphate was activated by magnesium ions. The finished cofactor then works inside enzymes such as transketolase, and each of the two active sites in human transketolase holds one thiamin diphosphate and one magnesium. In laboratory tests the enzyme bound its thiamin cofactor only when magnesium was there.^3,4

NIH uses the same enzyme as an indirect gauge of thiamin status, comparing transketolase activity in red blood cells with and without added thiamin diphosphate.¹

These are findings about enzymes in laboratory settings. They show the two nutrients working in the same pathway. They do not show that a magnesium supplement changes how well a thiamin supplement works in someone who already gets enough of both.

Where their everyday roles overlap

Both appear on the EU list of permitted nutrient statements for normal functioning of the nervous system, and both are tied to energy-yielding metabolism. The statements are quoted below with their grades.^7,8

Contributes to normal energy-yielding metabolism*^1,7,9

Moderate evidence

Thiamin is needed by the enzymes that release energy from food: as thiamin diphosphate, it is a cofactor for five enzymes that break down sugars, amino acids and fats. 'Contributes to normal energy-yielding metabolism' is the wording European regulators permit for thiamin after EFSA review. It does not mean extra thiamin gives more energy to someone who already gets enough.

Amount studied: Recommended intake: 1.2 mg a day for men and 1.1 mg for women, from all sources

Contributes to normal functioning of the nervous system*^7,10

Moderate evidence

A long-established role of the vitamin, included in the EU list of permitted nutrient-function statements after EFSA review. EFSA explains that the brain and nerves depend on thiamin diphosphate, because enzymes that need it help make the chemical messengers acetylcholine and GABA. It does not mean extra thiamin changes how the brain or nerves work in people who already get enough.

Amount studied: Recommended daily intake from food and supplements

Contributes to normal muscle and nerve function*^2,8,11

Moderate evidence

A long-established role of the mineral, described by NIH and included in the EU list of permitted nutrient-function statements. It does not mean extra magnesium improves performance in people who already get enough: a meta-analysis of 14 trials found no significant gains in muscle strength or power, with benefits appearing only in groups likely to be short of magnesium, such as older adults.

Amount studied: Recommended daily intake from food and supplements

None of these statements means that extra helps someone who already gets enough. The gap between the two is who is likely to fall short: about 6% of US adults had thiamin intakes below the average requirement, while 48% took in less magnesium from food and drink than its average requirement.^1,2

How each is absorbed

At usual intakes the gut absorbs more than 95% of thiamin, through a carrier that fills up. Above about 5 mg a day, a smaller share is absorbed.^1,10

Thiamin has a short half-life and the body stores little, so people need a regular supply from their diet.¹

In a study of magnesium taken with a standard meal, the share absorbed fell from 65% at the lowest amount to 11% at the highest, although the total absorbed still rose.⁵

The share of magnesium the gut absorbs is higher when it is taken in several small amounts through the day than in one large amount.¹²

Both reward moderate amounts. Past about 5 mg a day the gut takes up a smaller share of thiamin, and the share of magnesium absorbed shrinks as the dose grows, so bigger single doses of either give diminishing returns.^1,5

Neither NIH sheet names a time of day for its nutrient, and no study tested the pair at different times. The one sleep trial of magnesium bisglycinate had people take it 30 to 60 minutes before bed, and thiamin's short half-life means a regular daily supply matters more than the clock.^1,13

Adding up the amounts

Thiamin and magnesium for adults^1,2,5,14
Adults	Thiamin	Magnesium
Recommended a day	1.2 mg for men, 1.1 mg for women	400 to 420 mg for men, 310 to 320 mg for women
Upper limit	None set	350 mg a day from supplements and medicines
Absorption at higher doses	A smaller share above about 5 mg a day	A smaller share as the dose rises
Reported effect of high intakes	No adverse effects reported at 50 mg a day or more	Loose stools, nausea, cramping

What’s in ours

Men's Multi: Vitamin B1, 7 mg per serving, from the label

What’s in ours

Magnesium Glycinate: Magnesium, 275 mg per serving, from the label
Men's Multi: Magnesium, 50 mg per serving, from the label
Creatine + Electrolytes: Magnesium, 60 mg per serving, from the label

Men's Multi has both nutrients, and Magnesium Glycinate would add to the magnesium in it:

Our Magnesium Glycinate with our Men's Multi

Magnesium Glycinate and Men's Multi together provide 325 mg of magnesium a day, close to the 350 mg upper limit for magnesium from supplements. Do not add another magnesium product.

Hospital use, medicines and who should ask first

The strongest evidence for the pair comes from a hospital rather than a supplement shelf. In 36 people with long-term alcohol dependence treated in an emergency department, transketolase activity in red blood cells rose more when an injectable thiamin product was given with magnesium sulfate than when it was given alone. Doses and routes like that are chosen by clinicians, and the result says nothing about pills taken at home.⁶

No upper limit has been set for thiamin, because no harm has been reported from high intakes. Absorption falls above about 5 mg a day, and what the body does not need leaves in urine.^1,10

The upper limit for magnesium from supplements and medicines is 350 mg a day for adults. It does not count magnesium in food and drinks.^2,14

High intakes of magnesium from supplements and medicines can cause diarrhea, nausea and abdominal cramping.¹⁴

Your doctor may want to check on you

Furosemide, a loop diuretic, has been linked in research to lower thiamin levels, possibly low enough to be deficient, because more thiamin is lost in urine. NIH says people who take it regularly should discuss their thiamin status with their health care providers.^1,9,15

Reported in studies

Ask your pharmacist or doctor first

Long-term use of loop diuretics such as furosemide, and of thiazide diuretics such as hydrochlorothiazide, can increase the magnesium lost in urine, while potassium-sparing diuretics such as spironolactone reduce it. The furosemide label says it may lower blood magnesium and that levels should be checked periodically.^2,14,16

On the medicine's label

Ask first if you drink heavily or are recovering from alcohol dependence. Long-term heavy drinking lowers how much thiamin the gut absorbs and the liver stores, and the right plan is a medical one.¹
Ask first if you take furosemide or another loop diuretic, because both nutrients can be lost in urine and your care team may want to check them.^1,2
Ask first if you have kidney disease or reduced kidney function, because the kidneys remove extra magnesium.²
Ask first if you are having chemotherapy with fluorouracil, which has been linked to severe thiamin shortage.¹
Ask first if you take a tetracycline or quinolone antibiotic, a bisphosphonate, gabapentin or levothyroxine, because magnesium can lower how much of them is absorbed.¹⁴
Do not take thiamin if you have ever had an allergic reaction to it, including to a thiamin injection.¹⁷
Ask first if you are pregnant, especially with frequent or lasting vomiting, or breastfeeding.¹

Questions people ask

Can you take thiamine and magnesium at the same time?

NIH gives no spacing rule for this pair. The spacing advice that exists for magnesium concerns certain medicines, not thiamin. Magnesium is absorbed in a larger share from several small amounts than from one large one, so splitting a bigger dose is the more useful habit.^1,12,14

Does thiamine need magnesium to work?

In the laboratory, yes at two points. The enzyme that makes thiamin diphosphate was activated by magnesium in rat liver, and human transketolase bound its thiamin cofactor only when magnesium was present. No trial has tested whether magnesium pills change how thiamin pills work in healthy people.^3,4

What is the best time to take thiamine and magnesium?

No study has tested a best time for the pair. In the one sleep trial of magnesium bisglycinate, people took it 30 to 60 minutes before bed, and NIH gives no time of day for thiamin.^1,13

Is thiamine with magnesium too much?

Thiamin has no upper limit, because no harm has been reported from high intakes. Magnesium from supplements and medicines has an adult limit of 350 mg a day, so the thing to add up is the magnesium in every product you take.^1,2

See what we make

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See the Full Measure line Creatine + Electrolytes Magnesium Glycinate Men's Multi

Sources

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.