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Brain fog and trouble concentrating: common causes

Brain fog is not a diagnosis. It is a feeling of slow, unclear thinking, and most of the time it has an ordinary, fixable cause.

Common causes

  • 01Too little or poor-quality sleep, a very common cause
  • 02Low mood, anxiety or ongoing stress
  • 03Vitamin B12 deficiency (more likely if you are vegetarian or vegan, or take metformin or acid-reducing medicines)
  • 04Iron-deficiency anaemia
  • 05Underactive thyroid
  • 06Side effects of medicines, and alcohol

In women, low iron from periods is a common hidden cause.

As you get older. Thyroid problems and poor sleep become more common with age.

What a doctor may check

A doctor may check a full blood count, ferritin, vitamin B12 and thyroid (TSH).

When to see a doctor

Call emergency services now if it comes on suddenly, or with confusion, face drooping, arm weakness, slurred speech or vision loss. These can be signs of a stroke.

This page is general information, not a diagnosis. Venva's content is written against clinical guidelines and systematic reviews, listed below. See our medical disclaimer.

References

  1. 1.Vitamin B12 deficiency. Nature Reviews Disease Primers, 2017.doi:10.1038/nrdp.2017.40
  2. 2.Iron-deficiency anemia. New England Journal of Medicine, 2015.doi:10.1056/NEJMra1401038
  3. 3.Hypothyroidism. The Lancet, 2017.doi:10.1016/S0140-6736(17)30703-1
  4. 4.Recommended amount of sleep for a healthy adult: AASM/SRS consensus statement. Sleep, 2015.doi:10.5665/sleep.4716

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