The Impact of Insulin on Brain Fog

Do low blood sugar levels impact your brain and cause brain fog? Learn how the two may be connected.

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Merve Ceylan
— Signos
Health Writer & Dietitian
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Reviewed by

Merve Ceylan
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Updated by

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Science-based and reviewed

April 23, 2024
March 28, 2024
— Updated:

Table of Contents

Brain fog is commonly used to describe a decline or dysfunction in cognitive functions, such as difficulty concentrating, processing information, forgetfulness, and decreased verbal fluency. Since the brain is an organ that uses 20% of the body's energy, the relationship between metabolism and brain fog is being questioned. Insulin, a hormone crucial in energy metabolism, cell growth, repair, and neurological functions, can impact brain health. Read more to discover insulin's role in the common phenomenon of brain fog.


What Is Brain Fog?

The term 'brain fog' is often used but lacks a scientific or clinical definition. It's generally used to describe difficulty in cognitive functions. A 2023 study reported that people describe brain fog as having forgetfulness, poor concentration, perceived cognitive slowness, difficulty communicating, headaches, dizziness, fatigue, and emotional numbness.1

Brain fog is also commonly associated with COVID-19. The same study reported that most people experiencing brain fog thought the cause was COVID-19, withdrawal from recreational drugs, psychiatric diseases, and medications. The researchers concluded that the term 'brain fog' can refer to different experiences among people.

Considering there is no scientific or clinical definition we can use to address brain fog, this article will focus on insulin's effects on symptoms commonly used to describe brain fog.

How Insulin Affects the Brain? 

Insulin is a crucial hormone in regulating energy metabolism. It carries glucose from the bloodstream to cells. Different glucose transporters are present in our body. While some of them are insulin-dependent, others are not.  It has been believed that the brain is insulin-insensitive since most of the brain cells do not need insulin to uptake glucose. However, recent studies showed that certain brain cells are sensitive to insulin.2

Therefore, changes in insulin function can influence brain health, especially cognitive and memory functions, to such an extent that researchers have been exploring the potential of intranasal insulin delivery for the early treatment of Alzheimer's disease.3

In a clinical study, thirty-eight healthy individuals were administered insulin intranasally (through the nasal cavity) to evaluate insulin effects on memory, attention, and mood. After eight weeks, individuals administered intranasal insulin had significantly higher words recalled and reported enhanced mood, self-confidence, and reduced anger.4

Some research indicates that cerebral insulin is locally produced in the brain. However, the effects of peripheral (insulin produced by the pancreas) and cerebral insulin in the brain and the relationship between the two remain subject to further research.5

The degree to which brain insulin is affected by peripheral insulin remains a question for further research; peripheral insulin metabolism has also been associated with cognitive functions and brain health in general.

<p class="pro-tip"><strong>Also Related: </strong><a href="period-brain-fog">Period Brain Fog: Your Menstrual Cycles and Cognitive Function</a>.</p>

Insulin Resistance and Cognitive Functions

Woman with headache and brain fog

Insulin (peripheral insulin) is a hormone produced by the pancreas. Insulin resistance occurs when insulin is not as effective as it should be. Cells become less receptive to insulin, so blood glucose levels stay elevated. The body produces even more insulin to lower blood glucose; however, because the cells are not responsive, blood glucose and insulin levels remain higher than normal. If not treated, insulin resistance evolves into type 2 diabetes.

Insulin resistance and diabetes have been associated with both cognitive functions and mental health. 

Communication Difficulties and Brain Fog

People experiencing 'brain fog' have reported difficulty finding simple words, slurring words, and stuttering, all of which can cause communication difficulties. A study investigated the effects of type 2 diabetes on brain atrophy (gradual loss of brain cells) and dementia in older people aged 55 to 90 years over four years. The results showed that type 2 diabetes patients had a faster decline in verbal memory and fluency.6

Forgetfulness and Brain Fog

Forgetfulness is one of the most common complaints people associate with brain fog. It involves forgetting the places where they put items and struggling with both short-term and long-term memory problems. A longitudinal study followed pre-diabetic patients for around two to four years. The results reported that lower insulin sensitivity (lower insulin function) was significantly associated with a memory decline.7

Attention Deficiency and Brain Fog

Poor concentration, an inability to focus for even half a minute, difficulty reading books, or understanding conversations are common problems reported by people struggling with brain fog. A study investigated the association between the symptoms of attention-deficit/hyperactivity disorder (ADHD) and type 2 diabetes. The results reported that almost half of the participants had met the DSM-5 criteria for ADHD, and more than 13% of participants had either received an ADHD diagnosis or were taking ADHD medications.8

Fatigue and Brain Fog

Fatigue, having no energy, feeling weak, and exhaustion are just a few problems some people associate with brain fog. Higher fatigue was related to lower sleep quality and increased depressive symptoms in people with a recent diabetes diagnosis. Unfortunately, patients experiencing fatigue are less likely to incorporate physical activity and healthy eating into their lives, which can further feed the cycle.9

Poor Mental Health and Brain Fog

People experiencing 'brain fog' have reported emotional numbness, lack of social awareness, feeling distant from others, and not enjoying activities they normally enjoyed very much in the past. A study investigated the prevalence of mental health problems in type 2 diabetes. The results showed that 19% of patients had mental health problems, with the most common being depression.10

Brain fog, often described as a decline in cognitive abilities such as concentration, memory, and verbal fluency, has been reported to be altered in patients with insulin resistance and diabetes. While the brain was traditionally thought to be insulin-insensitive, recent research indicates that insulin sensitivity in certain brain cells plays a role in cognitive health. Moreover, insulin resistance has been implicated in cognitive decline and mental health problems. Therefore, improving insulin sensitivity with lifestyle interventions such as healthy nutrition, regular exercise, and adequate sleep can help enhance cognitive health and mental well-being.

How Signos Can Help

Signos is here to help you track and evaluate progress as you incorporate lifestyle interventions to manage your mental health and blood sugars

‍Learn more about Signos and take the quick free quiz to determine if it’s the next right step for you and your health and wellness goals.

<p class="pro-tip"><strong>Learn More: </strong><a href="increase-insulin-sensitivity">How to Improve Insulin Sensitivity</a>.</p>

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Topics discussed in this article:


  1. McWhirter, L., Smyth, H., Hoeritzauer, I., Couturier, A., Stone, J., & Carson, A. J. (2023). What is brain fog?. Journal of Neurology, Neurosurgery & Psychiatry, 94(4), 321-325.
  2. Gray, S. M., Meijer, R. I., & Barrett, E. J. (2014). Insulin regulates brain function, but how does it get there?. Diabetes, 63(12), 3992-3997.
  3. Long, C., Han, X., Yang, Y., Li, T., Zhou, Q., & Chen, Q. (2022). Efficacy of intranasal insulin in improving cognition in mild cognitive impairment or dementia: a systematic review and meta-analysis. Frontiers in Aging Neuroscience, 14, 963933.
  4. Benedict, C., Hallschmid, M., Hatke, A., Schultes, B., Fehm, H. L., Born, J., & Kern, W. (2004). Intranasal insulin improves memory in humans. Psychoneuroendocrinology, 29(10), 1326-1334.
  5. Blázquez, E., & Velázquez, E. (2014). Insulin in the brain: its pathophysiological implications for States related with central insulin resistance, type 2 diabetes and Alzheimer’s disease. Frontiers in endocrinology, 5, 109263.
  6. Callisaya, M. L., Beare, R., Moran, C., Phan, T., Wang, W., & Srikanth, V. K. (2019). Type 2 diabetes mellitus, brain atrophy and cognitive decline in older people: a longitudinal study. Diabetologia, 62(3), 448-458.
  7. Willmann, C., Brockmann, K., Wagner, R., Kullmann, S., Preissl, H., Schnauder, G., ... & Heni, M. (2020). Insulin sensitivity predicts cognitive decline in individuals with prediabetes. BMJ Open Diabetes Research and Care, 8(2), e001741.
  8. Dehnavi, A. Z., Zhang-James, Y., Draytsel, D., Carguello, B., Faraone, S. V., & Weinstock, R. S. (2023). Association of ADHD symptoms with type 2 diabetes and cardiovascular comorbidities in adults receiving outpatient diabetes care. Journal of Clinical & Translational Endocrinology, 32, 100318.
  9. Kuo, H. J., García, A. A., Huang, Y. C., Zuñiga, J. A., Benner, A. D., Cuevas, H., ... & Hsu, C. Y. (2023). Impact of Fatigue and Its Influencing Factors on Diabetes Self-Management in Adults With Type 2 Diabetes: A Structural Equation Modeling Analysis. The Science of Diabetes Self-Management and Care, 49(6), 438-448.
  10. Guerrero Fernández de Alba, I., Gimeno-Miguel, A., Poblador-Plou, B., Gimeno-Feliu, L. A., Ioakeim-Skoufa, I., Rojo-Martínez, G., ... & Prados-Torres, A. (2020). Association between mental health comorbidity and health outcomes in type 2 diabetes mellitus patients. Scientific reports, 10(1), 19583.

About the author

Merve Ceylan is a dietitian and health writer.

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