Accessible biomarkers have gained interest in recent decades for the possibility of observing actionable lifestyle changes which may promote health and longevity. Glucose is one such biomarker which has received some attention with its role in overall metabolic health. The links between glucose management and diabetes are well documented and some of the physiology is thought to also play an important part in general healthy physiology.
Stabilising glucose and preventing high glucose concentrations is a common theme in many longevity-focused discussions. Lesser glucose variability and the association with reduced HbA1c take centre stage in the discussion. While associations are observed between lower glucose variability and reduced HbA1c, these findings only reflect concurrent relationships and cannot determine whether one influences the other. As such, the results may represent coincidental patterns rather than true physiological effects. At present, there is little evidence that managing variability offers any health benefit beyond helping to prevent or detect those at heightened risk of metabolic disorders.
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What Are Glucose Levels?
This refers to the concentration of glucose appearing in the blood. Concentration is a constant state of flux between appearance and disposal. Appearance is tightly linked to eating food. When we eat, the food is broken down and digested, releasing nutrients into the system. This post-consumption phase is known as the “post-prandial period” and is generally reflected by a rise in blood glucose. This rise can also occur during stressful periods to provide fuel to the body to combat the stress in a “fight or flight response” such as during exercise.
When this rise is detected, transporters and gates at the cell level activate to accept the new nutrients and glucose. After a period of time, this transfer from blood to cells and organs tails off and blood concentrations return to normal. This is a very normal part of the digestive, absorptive process. The rise in concentration signals the uptake of the given nutrient.
In the case of glucose, a rise is detected and triggers the release of insulin. The insulin acts as the key holder to open the gate on the cell membrane, which allows glucose to enter the cell. So, with a rise in glucose, we also see a rise in insulin.
In the case of exercise, glucose transporters (GLUT4) act as additional channels, substantially increasing the amount of glucose that can be absorbed into the muscles. This makes activity one of the best mechanisms for bringing glucose concentrations back down to normal levels.
What Are Normal Concentrations?
Normal concentration is highly debated, as concentrations in the fasted versus fed state will differ vastly. Any presence of a metabolic disorder will also impact how different concentrations are viewed. Typically, normoglycaemia is considered a concentration from 72-99 mg/dL or 4 to 5.4 mmol/L. Concentrations in excess of 99 mg/dL are normal in the postprandial period but they would be expected to return to normal within approximately two hours in most cases. To assess a functioning glycaemic response, an Oral Glucose Tolerance Test (OGTT) may be used to examine this process. Should concentrations remain high (hyperglycaemia) post-consumption of a fixed carbohydrate amount or exceed the expected rise, then it is assumed that there is some degree of glucose intolerance, typically caused by some underlying insulin desensitization.
Low blood sugar (hypoglycaemia) is also concerning. Glucose is the critical energy molecule our cells need to survive. The brain in particular is reliant on glucose as fuel, and there are several safety mechanisms in place to ensure a minimum supply; without it, brain death will occur. Mild hypoglycaemia can lead to confusion and impede cognitive performance. While severe hypoglycaemia is rare in healthy individuals, it is a dangerous event in those with Type 1 diabetes. Nonetheless, high degrees of glucose variability (swings in concentration) can bring on some hypoglycaemia. Often the natural endocrine response to correct hyperglycaemia may overshoot its task and create short periods of hypoglycaemia, which are often transient in nature. This is known as reactive hypoglycaemia.
What Is Metabolic Health?
Metabolic health is a reflection of a number of systems and processes which interact with each other. When all organs work well, the system generally works well. In the case of diabetes, the pancreas is the broken link in the chain. Lifestyle has a major part to play in our metabolic health: if we don’t use it, we lose it. The more active we are, the more we challenge the system and ask it to adapt and cope. This adaptation gives it capacity and maintains function. When we eat, we fuel our body to allow for activity. The issue arises when we stop being active but continually eat and over fuel. Excess energy is stored as adipose tissue. Excessive accumulation extends into the blood, where fat circulates in the form of triglycerides, detectable in blood tests. Excessive fat accumulation around the organs interrupts their function, particularly the liver. This leads to further accumulation and inflammation of organs. Eventually, this hinders the ability of insulin to work effectively, meaning glucose does not exit the bloodstream as well as it once did, and we see heightened concentrations.
Eventually, these heightened concentrations place additional pressure on the pancreas to secrete additional insulin. The net result of this is that we become desensitised to insulin and may struggle to produce enough, while glucose accumulates in the blood. This accumulation rarely gets to toxic levels in someone free of diabetes, but should the pancreas fail, then concentrations may become toxic. This can lead to nerve damage and vascular degeneration, which can impact the eyes and the extremities.
Certain risk factors such as high levels of adipose tissue and inactivity contribute significantly to the decline in metabolic health. The progressive decline leads to the development of disease and comorbidities such as Type 2 diabetes, cardiovascular disease and several others, which significantly impact longevity.
Glucose Spikes: Are They Always Bad?
The general media is very concerned about glucose spikes. This appears to be the core concern for those looking to optimise their health. A glucose spike is a loose term; glucose excursion is the correct phrase, and it is defined as a rise above baseline that exceeds a certain threshold. These thresholds vary depending on who is examining them. Excursions are generally measured using the mean amplitude of glucose excursion (MAGE). Other metrics such as time in range are also used to observe general daily fluctuations with time spent above range being equally concerning. For healthy individuals with a functioning pancreas, there is little evidence that spikes are abnormal. When a natural correction occurs, there is little to be concerned about. This is not the case with Type 1 diabetes, where glucose spikes can reach toxic levels and may remain uncorrected without appropriate insulin therapy. This process is often confused in the media with the physiology of Type 1 diabetes, which is assumed to apply to healthy individuals.
Glucose Concentration as a Symptom
For healthy individuals concerned with longevity or the potential development of declining metabolic health, blood glucose should be viewed more as a symptom than a cause. Heightened concentrations are the sign that something in the underlying physiology is off. While these concentrations may not reach the threshold for clinical concern, sustained elevated concentrations may be the first signs of developing insulin resistance. There are several tests which can be used to assess this. First is fasted glucose measurement; this indicates the general maintenance of glucose concentrations in the blood as the concentration is not impacted by food intake. It allows us to see how physiology works in the background. This can be somewhat impacted acutely and does not tell the full picture over time. To account for this, glycated haemoglobin can be assessed. Red cells in our blood can become coated with glucose over their lifecycle, typically three months. By measuring the levels of glycation, we can determine the levels of exposure to high glucose concentrations over time. This is reflected by HbA1c measurements, which should sit below 5.7%.
Additionally, one can assess insulin resistance using a Homeostatic Model Assessment for Insulin Resistance (HOMA-IR). Depending on the model, the value obtained can indicate various levels of insulin resistance, although the exact threshold for concern is debated amongst clinicians.
What Is Continuous Glucose Monitoring and Why Is It Important?
Continuous Glucose Monitoring (CGM) has been a truly revolutionary advance in the management of diabetes. It allows the user a convenient, discreet method of tracking their glucose concentrations in real time. Not only does this allow them to take immediate actions if required, but it also allows them to collect deep insights into the variances and patterns within their own personal physiology. While CGM technology is not without its limitations, the efficacy of the technology has advanced substantially in recent decades to produce a very useful support tool.
We know CGM is an effective tool in managing diabetes, but its utility outside of that sphere is debatable. What good is knowing glucose concentrations if they are normal? A healthy individual has no action to take and no real use for what can be a costly piece of technology. The hype and marketing surrounding wearable technology often exceed the evidence base and this is somewhat true for CGM.
In isolation, CGM might do little for longevity. As part of a greater toolbox of early detection and management tools, it becomes quite a useful option. There is a substantial argument for the use of CGM to aid in the development of a better lifestyle through changes in behaviour, both from an educational and accountability standpoint. Real-time feedback is engaging and compelling and plays a significant role in supporting a change in lifestyle, which may be needed to steer an individual onto a better path before real pharmaceutical intervention is required.
Practical Ways to Support Healthy Glucose Levels
Managing the glycaemic impact of food is one of the best ways to stabilise glucose levels and reduce daily variability. Choosing low glycaemic index carbohydrates is a very simple strategy. This includes whole grain versions of regular white carbohydrates, pasta and bread, for example. The inclusion of fibre and protein can also slow the release of glucose during digestion and reduce variation. Reducing the intake of sugary food sources like confectionery or fizzy drinks should also be considered.
In terms of exercise support, being active helps the disposal of glucose through increased glucose utilisation. In addition, lean muscle mass is considered a metabolically active tissue. This means maintaining muscle mass through regular resistance training can help support the disposal of glucose from the circulatory system.
When Should You Speak to a Healthcare Professional?
Regular checkups typically screen for the development of major risk factors, however, these are generally age-specific. Not all GPs will check fasting glucose unless there is a genuine reason. An unhealthy lifestyle or weight gain doesn’t automatically trigger the assumption that an underlying metabolic disorder is present because it may not be. And those with a healthy weight and an average lifestyle, by contrast, may develop conditions regardless. In this respect, metabolic disorders can silently develop as their symptoms may not be obvious until the conditions are fully developed. In the case of more severe symptoms such as extreme thirst, frequent urination, fatigue and sudden weight loss; these should be investigated further as they may be an indication of adult-onset Type 1 diabetes.
Final Takeaway: Glucose Is One Part of the Longevity Puzzle
Glucose is a useful insight into metabolic health, but it isn’t the whole picture, and it certainly won’t cause ageing on its own. It’s a symptom that reflects how well the underlying system – activity levels, muscle mass, body composition, sleep and stress – combine and interact. Chasing reduced concentrations and zero spikes alone misses the point: a healthy pancreas and healthy tissues will naturally produce some rise and fall, and that’s not something to be concerned with. What matters far more for longevity is the lifestyle routines like staying active, maintaining muscle, not over fuelling a body that isn’t moving enough to use the fuel. Glucose monitoring, whether through a fasting blood test, an HbA1c, or a CGM, is best used as one input among several, helping to flag when the underlying physiology is starting to drift, rather than as a daily scorecard to be optimised for its own sake. Used this way, it’s a genuinely useful piece of the puzzle, but other factors still must be factored into the overall longevity strategy.
Frequently Asked Questions
What is a healthy glucose level?
Typically, normoglycaemia is considered a concentration from 72-99 mg/dL or 4 to 5.5 mmol/L.
Are glucose spikes bad if I do not have diabetes?
No, there is natural variation in glucose concentrations. Sudden rises and falls are normal as long as concentration stabilizes within a reasonable timeframe.
What causes glucose levels to rise after meals?
The release of glucose into the bloodstream from the digestion of carbohydrates.
How does glucose affect metabolic health?
Constantly elevated glucose concentrations can contribute to the development of insulin resistance, but glucose is regarded more as a symptom of other issues rather than a cause of metabolic decline.
Can high glucose levels affect longevity?
In isolation, without diabetes, glucose has little direct impact. In the case of diabetes and in combination with other metabolic disorders, extreme levels can have a detrimental impact. This is uncommon in otherwise healthy individuals.
What is the link between insulin resistance and ageing?
Insulin resistance generally increases with ageing as lifestyles become more sedentary and other health decrements combine to promote the development of general metabolic declines.
What foods cause the biggest glucose spikes?
Carbohydrates with a high glycaemic index generally eaten in large amounts ie. confectionary, white bread, white rice and regular fizzy drinks
Is fasting good for glucose control?
Fasting avoids a spike simply because there’s no glucose load to respond to, and it also actively shifts the hormonal environment (lower insulin, higher glucagon) toward improved insulin sensitivity, though how much of that benefit is fasting-specific versus a byproduct of eating less overall is still genuinely debated.
When should I get tested for prediabetes or diabetes?
As a preventive measure as you age, it is a good idea to be screened for general risk factors. If experiencing any of the typical symptoms discussed above it is worth seeking guidance from a health professional.