October 31 2025 | Last Updated October 31 2025

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Just like most things in life, there is an optimal zone when it comes to targeting our blood sugars.

This article walks you through the basics of blood sugar targets for dementia prevention.

What are the possible blood sugar ranges?

Blood sugars can range from low, to normal, to high.

Below, we walk you through what each range looks like and what it means for the brain.

*Finger-prick testing is used to monitor blood sugar levels in the moment.*

Low Blood Sugar

Low blood sugar (called “hypoglycemia”) is anything less than 3.9 mmol/L using a finger-prick glucose meter.

Low blood sugars are an immediate concern. Having a low sugar can lead to symptoms like brain fog, fatigue, irritability, weakness, and eventually even seizures or a coma if it becomes severe enough.

Having frequent low blood sugars can also impact our brain health over the longterm. Our brains need sugar to live - just like how our bodies need oxygen. Repeated moments of “no oxygen” obviously leads to damage, and the same is true for “no sugar” moments and the brain.

Normal Blood Sugar

The sweet spot for day-to-day blood sugar levels is between 4.0 - 7.0 mmol/L on finger-prick testing. If you have diabetes, the range is a bit higher (4.0 to about 10.0 mmol/L), but can vary depending on your personal circumstances.

Sugars in this range do a good job of providing adequate energy to your body and brain, without causing damage to your arteries and other organs.

In addition to looking at “in-the-moment” blood sugar levels using the finger-prick testing, healthcare providers often also order a HbA1C test, which looks at your average blood sugar over the last 3 months. A normal HbA1C is around 5.7%.

High Blood Sugars

High blood sugars (called “hyperglycemia”) are generally above 8 - 10 mmol/L after eating.

High blood sugar levels cause problems over the longterm as the excess sugar travels around your body and can damage your arteries and other organs, including your brain.

Extremely high blood sugar levels can cause immediate symptoms like confusion, agitation, and weakness, and can become a medical emergency if left untreated.

*Ranges for finger-prick testing using a glucometer.*

What is Diabetes?

The condition known as “diabetes” is diagnosed when your 3 month average blood sugar level (called your HbA1C) is more than 6.5%.

In diabetes, your body is no longer processing sugar as well as it used to. This means excess sugar is left in your blood stream, leading to these high numbers.

The goal for everyone - with or without diabetes - is to keep your blood sugar in the normal range the majority of the time.

*Having sugars frequently above the normal range leads to a HbA1C above 6.5%, which is classified as diabetes.*

What is the optimal HbA1C for dementia prevention?

If you do not have diabetes

Your HbA1C is already in the optimal range.

For you, blood sugar control is more about learning to eat in a way that doesn’t spike your sugars high or low, even within the normal range.

This helps to ensure you have a consistent energy source throughout the day to avoid feeling fatigue, brain fog, etc.

*Eating balanced meals at regular times can help to keep your blood sugar levels steady, avoiding brain fog, fatigue, and other symptoms.*

If you do have diabetes

The optimal HbA1C range for dementia prevention is between 6.5 - 7.5%.

Studies have shown that getting your HbA1C lower than 6.5% can actually lead to worse brain health outcomes. This is likely because to get such “tight” control, you end up with occasional low-sugar moments, which are very bad for the brain.

Keeping your HbA1C between 6.5-7.5% optimizes your levels while avoiding both lows and highs.

The caveat to this would be if your healthcare provider thinks you can reverse your diabetes entirely through diet, exercise, and weight loss (i.e. cure). In this case, there could be a role for targeting a lower HbA1C with careful monitoring from a healthcare professional.

*Optimal blood sugar is all about balance - not too high, and not too low.*

Timing Matters

Early and Mid Life

When we are in our 20’s - 70’s, we typically want your blood sugars to be optimized the majority of the time. If you have diabetes, this is the ultimate time to get it under control.

Studies show that a mid-life diagnosis of diabetes (meaning in your 40’s-70’s) increases your risk for dementia.

Late-Life

Late-life diagnosis of diabetes doesn’t seem to have the same effect on brain health. This may be because excess sugar causes damage over many years, and you may or may not have enough time for that late in life!

Instead, the focus shifts to making sure you don’t have any low blood sugars, since these are more dangerous for the brain in the short-term.

*Just like how our priorities change at different stages of life, our blood sugar targets can change as well.*

How can you improve your sugars?

There are four key methods to improve your blood sugar, each of which will have a dedicated Aldora article coming soon.

Nutrition
Exercise
Weight loss (through a combination of 1 and 2)
Medications (if your HbA1C is more than 7.5% despite trying methods 1-3)

*Eating well and moving more is the foundation of blood sugar regulation, however in some people medications may also be necessary.*

In Closing…

Blood sugar is important for our brain health. We don’t want it to be too low, and we don’t want it to be too high.

If you are not diabetic, you are already in the sweet spot with blood sugar levels between 4-7 mmol/L on a daily basis. The goal is to keep your sugars steady throughout the day.

If you are diabetic, the sweet spot for blood sugar levels is between 4 - 10 mmol/L on a daily basis, with a 3 month average HbA1C of 6.5%-7.5%. The goal is to avoid extremes of highs and lows.

By focusing on your blood sugar levels you can ensure your brain gets the energy it needs to function well for years to come.