Vitamin B1

What is vitamin B1?

Thiamine is a B vitamin with one main job: it sits as a helper in the enzymes that turn carbohydrates into energy. Without B1 the sugar gets stuck halfway and the energy does not come out. Tissues that demand a lot of energy and hold little reserve, your brain, your nerves and your heart muscle, notice that first. That is why a deficiency starts with tiredness, irritability and tingling in the feet, and in a severe case reaches the brain and the heart. What is special about B1 is how little of it you keep. Where vitamin B12 sits in your liver for years, your body holds a two- to three-week supply of B1. Eat one-sidedly for that long, or use more than comes in, and the store runs out. B1 is in whole grains, legumes, pork, nuts and seeds; white bread, white rice and sugar deliver the carbohydrates, but not the vitamin. Your report shows vitamin B1 in nmol/L. It is measured in whole blood rather than serum, because the active form sits in your red blood cells. Normal is about 100 to 170 nmol/L where the labs overlap; the range differs per lab more than for most values.

Why is vitamin B1 relevant?

A B1 deficiency is not rare in the Netherlands, it just gets little attention. The biggest reason is alcohol. Alcohol blocks the uptake of B1 in the gut, reduces the store in the liver and uses up the vitamin in its own breakdown, and anyone who drinks a lot often eats less too. So a deficiency can develop in someone who appears to eat normally. That is why a B1 value is so telling for anyone who drinks regularly: it shows whether the body still keeps up with what is being used, long before anything serious happens. The second group is everyone in whom the supply or the uptake falters: after stomach surgery, with prolonged vomiting, with one-sided eating heavy in white carbohydrates, and in anyone on long-term diuretics, because those flush B1 out in the urine. A heart that has to work hard, and a body that gets plenty of carbohydrates again after a period of eating little, also suddenly ask for more B1 than is there. What a deficiency does is very reversible if you catch it in time. A B1 deficiency affects the nerves, with tingling and numbness in feet and hands, and in a severe case the heart and the brain: confusion, loss of balance and memory loss that can become permanent. It never has to get that far, because the vitamin is cheap, safe and works within days.

Vitamin B1 reference ranges

The band above is where the labs overlap, and for vitamin B1 their own ranges run further apart than for most values: the lower limit differs by a factor of two between labs. So compare your value with the range on your own report. The national table for general practice names a lower figure, 60 to 120 nmol/L, and a value around 100 sits comfortably within that too. For B1 the lower end is what counts: a deficiency is the problem, a high value is not.

Vitamin B1 high or low: what it means

A low B1 means the supply fell short in recent weeks or the use ran higher. From common to rare: alcohol, one-sided eating heavy in white carbohydrates, stomach surgery, long-term use of diuretics, and rarely prolonged vomiting, dialysis or heart failure. With a low B1 and symptoms, tingling, confusion or palpitations, topping up is not something to wait on; the vitamin helps within days and can do no harm. A high B1 is almost always a supplement, a B complex or an energy drink with B vitamins. B1 dissolves in water and whatever you take in beyond need leaves your body in the urine, so a high value is harmless and has no known upper limit that anything belongs to. What you do about it: eat more whole grains, legumes, nuts and seeds, and less white bread, white rice and sugar. Drink less, because alcohol is the biggest bite out of your store. If you take diuretics or have had stomach surgery, a supplement or a B complex is a sensible habit, and B1 is too safe to be hesitant about. Magnesium belongs with it, because B1 only works with enough magnesium. Read B1 beside vitamin B6, which comes from the same tube, beside magnesium, and in anyone who drinks beside vitamin B12 and folate, because those deficiencies often go together. Repeat after a few weeks of topping up to see whether the store has been rebuilt.

How does a vitamin B1 blood test work?

Referral

Not needed. You can have vitamin B1 measured yourself, and the value usually comes back together with vitamin B6.

Fasting

Not needed, but skip the B complex on the day of the draw, otherwise you measure the supplement instead of your store.

The draw

One tube of whole blood from a vein in your arm, which has to reach the lab quickly because the vitamin is not stable for long after the draw; not possible at every location.

The result

A single number in nmol/L, with a range that differs considerably per lab; compare with the range on your own report.

Repeating

After a few weeks of topping up to see whether the store has been rebuilt; with ongoing alcohol use or after stomach surgery, yearly.

Where to draw

You can draw at 250+ locations near you, no referral needed. See the locations

Educational information only, not medical advice. Consult a healthcare professional for clinical decisions.