Do brain fog supplements work?
Only shown to help if you’re low in a vitamin or mineral. A blood test can show low B12 or iron. But the “reduces tiredness” line on the bottle proves less than it sounds.
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Do any vitamins help brain fog?
Mainly when they fix a lack. The NHS lists problems with memory, understanding and judgment as a sign of low B12 or folate. Many symptoms improve with treatment.
If you’re not low, the proof is thin. A Cochrane review, which pools the best trials, looked at 14 trials of B vitamins in 27,882 people with no thinking problems.
Most were in their 60s and 70s. Extra B vitamins probably made little or no difference to their thinking.
Think of a fuel tank. An empty one stops the car. Topping up a full one won’t make it go faster.
| Supplement | When it may help | What the evidence says |
|---|---|---|
| Vitamin B12 | A blood test shows you’re low | Low B12 can cause memory problems. Many symptoms improve with treatment. |
| Iron | A blood test shows iron deficiency anaemia | Low iron can cause tiredness and lack of energy. Treatment is usually iron tablets for about 6 months. |
| Folic acid | A blood test shows low folate | Your GP checks B12 first. Folic acid can hide a lack of B12. |
| Magnesium | No trial we found tests it for brain fog | The NHS says there’s not enough evidence to advise it for ME/CFS. |
| Vitamin D | Everyone in autumn and winter, for bones and muscles | A trial in older adults found no effect on thinking over up to 10 years. |
| Ginkgo | Not shown to help | Not proven for any condition studied. May raise bleeding risk with warfarin. |
Sources: NHS; NHS B12 treatment; NHS iron; NHS ME/CFS; NHS vitamin D; Cochrane; NCCIH
So the first job is to find out if your tank is low. That takes a blood test, not a bottle.
Felt tired for a few weeks and not sure why? The NHS says to see a GP.
Does B12 help brain fog?
It can, if you lack it. Low B12 can also cause pins and needles, a sore red tongue and problems with balance. Some damage can be permanent if it isn’t treated.
You’re more likely to be low if you:
- eat a vegan diet without B12 supplements or fortified foods
- take metformin, nitrous oxide, or PPIs (tablets that cut stomach acid)
- have had stomach surgery or have Crohn’s disease
- are a woman around 60, have another autoimmune condition (where the immune system attacks the body), or pernicious anaemia runs in your family
Pernicious anaemia, where your immune system stops you absorbing B12 from food, is the most common cause in the UK. That’s why it’s usually treated with injections, not a shop-bought tablet.
What usually happens if you might be low in B12
- 1
Blood test
Your GP looks at your symptoms and a blood test.
- 2
Injections first
Usually every other day at first, from a GP or nurse.
- 3
Tablets or injections
Tablets may be offered if diet is the cause. If not, usually injections every 2 to 3 months for life.
- 4
Check it worked
Often a blood test 7 to 10 days in, then about 8 weeks in.
Source: NHS
Take metformin or a PPI? Ask your GP if your B12 should be checked. Never stop or change a prescribed medicine without your prescriber.
More on signs of low B12 and the B12 blood test.
Does magnesium help brain fog?
No one knows yet. We found no trial that tests magnesium for brain fog. For ME/CFS (chronic fatigue syndrome), the NHS says there’s not enough evidence to advise it.
Your body does need it to turn food into energy. Adults aged 19 to 64 need 300 mg a day (men) or 270 mg (women). Spinach, nuts and wholemeal bread all have it.
High doses over 400 mg can cause diarrhoea. There’s not enough evidence on what high doses do over a long time.
Want to try it anyway? The NHS says 400 mg or less a day from supplements is unlikely to cause harm. See which magnesium to take.
Why does the label say “reduces tiredness”?
That line is a legal stock phrase. UK rules list set wordings, such as “Magnesium contributes to a reduction of tiredness and fatigue”.
Any product that counts as a source of magnesium may print it. B12 has its own: “contributes to normal psychological function”. Iron gets “contributes to normal cognitive function”.
Back to the fuel tank. A sign saying “fuel powers your car” is true. It doesn’t tell you if your tank is low.
So read the amount per tablet, not the claim. Then check it against the safe amounts below.
How much is safe to take?
| Supplement | Most adults need | NHS safe supplement amount |
|---|---|---|
| Vitamin B12 | About 1.5 micrograms | 2 mg or less a day is unlikely to cause harm. |
| Magnesium | 300 mg (men), 270 mg (women) | 400 mg or less a day from supplements is unlikely to cause harm. |
| Iron | 8.7 mg (men), 14.8 mg (women 19 to 49) | 17 mg or less a day, unless your GP advises more. |
| Vitamin D | 10 micrograms | No more than 100 micrograms (4,000 IU) a day. |
| Folic acid | 200 micrograms of folate | 1 mg or less a day is unlikely to cause harm. |
Sources: NHS vitamin B; NHS minerals; NHS iron; NHS vitamin D
Labels mix units. 2 mg of B12 is the same as 2,000 micrograms.
Before you buy a brain fog supplement
- See a GP if you’ve felt tired for a few weeks and don’t know why. Ask about a blood test.
- Consider 10 micrograms of vitamin D a day in autumn and winter, as the NHS advises for everyone.
- If you’re vegan, have B12 fortified foods or a B12 supplement.
- Keep magnesium supplements to 400 mg a day or less. The NHS says that’s unlikely to cause harm.
- Keep iron tablets out of children’s reach. An iron overdose can kill a young child.
- Taking warfarin or other medicines? Ask your pharmacist before ginkgo or other herbal remedies.
Sources: NHS; NHS vitamin D; NHS vegan diet; NHS iron; NCCIH
Foggy with hot flushes or period changes? The NHS says herbal remedies like black cohosh have very little evidence for how well they work or how safe they are. See menopause brain fog.
When to speak to a GP
Stress, anxiety, depression and poor sleep are common, treatable causes of memory problems. An underactive thyroid can make it hard to think clearly too. Book an appointment if:
- You’ve felt tired for a few weeks and don’t know why, or it affects your daily life.
- You feel tired and have weight loss or mood changes, or you’ve been told you gasp, snort or choke in your sleep.
- Memory problems are affecting your day-to-day life.
- You have signs of low B12, like pins and needles, a sore red tongue or problems with balance.
- You or a relative have slowly become more forgetful or confused.
Call 999 or go to A&E if someone suddenly becomes confused. Don’t drive yourself. Ask someone to drive you or call an ambulance.
See which tests a GP may use in brain fog blood tests. For memory in healthy people, see vitamins for memory.