A no-nonsense guide to blood sugar

You’ve probably heard the term blood sugar thrown around lately, be it on social media, in conversations with your doctor, or because you may have heard it out in public. It’s become a bit of a buzzword, with people tracking their glucose levels, talking about “spikes,” and trying to eat in ways that keep things steady. 

But beyond the trend, blood sugar isn’t just a wellness fad. It’s a key part of how your body works and can influence your energy,mood and long-term health, even if you don’t have diabetes.

What is blood sugar?

Blood sugar (or blood glucose) is the amount of sugar circulating in your bloodstream at any given time. It’s your body’s main source of energy, produced when carbohydrates from food are broken down during digestion.¹

After you eat, your blood sugar naturally rises. In response, the pancreas releases insulin, a hormone that helps move glucose from the blood into your cells, where it can be used for energy. Any extra glucose is stored for later or converted into fat.¹

In a healthy body, this system works smoothly, keeping energy levels steady throughout the day. But when blood sugar spikes too high or drops too low, that balance gets disrupted. Over time, those fluctuations may affect how you feel day-to-day.¹

Why blood sugar balance matters

Everyone can be affected by changes in blood sugar. Even in healthy individuals, large peaks and crashes can lead to low energy, cravings, poor focus, and irritability. Research is exploring links between long-term glucose patterns and metabolic health, but these effects vary between individuals

When your blood sugar is stable, your body has a consistent energy supply. You’re less likely to experience mid-afternoon slumps, sugar cravings, or sudden mood dips. In fact, balanced glucose levels may support steadier energy, sleep and mood for some people.

Understanding HbA1c

One of the most reliable ways to assess long-term blood sugar control is through a marker called HbA1c, or glycated haemoglobin.¹

Haemoglobin is a protein in red blood cells that carries oxygen around the body. Over time, glucose in your bloodstream binds to this protein, forming what’s known as glycated haemoglobin. The HbA1c test measures the percentage of haemoglobin that has glucose attached to it, providing an average of your blood sugar levels over the past 90 days (the typical lifespan of a red blood cell).^1,3

• Below 6% (42 mmol/mol): normal range

• 6-6.4% (42-47 mmol/mol): prediabetes

• 6.5% (48 mmol/mol) or higher: diagnostic for diabetes

*HbA1c results should be interpreted by a clinician if they fall outside the normal range.

The HbA1c test is useful because it gives a broader view of blood sugar control over time, rather than a snapshot from a single reading. For people with diabetes, it’s an important tool to help manage treatment and reduce the risk of long-term complications like kidney damage, nerve issues, or heart disease.

Even for those without diabetes, an HbA1c test may help identify patterns worth discussing with a clinician. 

What causes blood sugar highs and lows?

While food plays a major role, it’s not the only factor influencing your blood sugar.

1. What you eat

Simple carbohydrates like white bread, pastries, or sugary drinks are digested quickly, causing rapid spikes in blood sugar followed by equally sharp crashes. In contrast, complex carbs (like oats, wholegrains, and beans) are digested slowly, keeping levels more stable. Pairing carbs with protein, fibre, and healthy fats can also help moderate your response to food.⁴

2. Stress

When you’re stressed, your body releases cortisol, a hormone that can increase blood sugar and may reduce insulin sensitivity.  Chronic stress can therefore keep blood sugar levels high and reduce your cells’ sensitivity to insulin.⁵

3. Sleep

Poor sleep has been linked to blood sugar issues. Research shows that people who sleep less than six hours a night or have irregular sleep patterns could have higher glucose levels and more pronounced spikes after meals. Going to bed earlier and maintaining a consistent sleep schedule can make a noticeable difference.⁶

4. Hormones

In women, blood sugar balance can shift throughout the menstrual cycle. Insulin sensitivity tends to be higher during the first half of the cycle, and lower in the second half when progesterone rises. This may help explain sugar cravings and fatigue before a period.⁷

Practical ways to support healthy blood sugar

You don’t need a wearable sensor or complicated diet plan to keep your blood sugar in check. Here are a few simple, science-backed strategies:

1. Eat balanced meals: Combine carbs with protein, fibre, and healthy fats to slow down digestion and keep your energy levels steady.

2. Choose complex carbs: Opt for wholegrains, beans, and lentils over refined carbs like white rice or bread.

3. Move after meals: Even a 10-minute walk after eating can help lower post-meal blood sugar levels by using up glucose as energy.

4. Manage stress: Techniques like yoga, breathing exercises, or meditation can reduce cortisol and help stabilise glucose levels.

5. Sleep more: Aim for 7–9 hours of quality sleep each night to support insulin sensitivity and hormone balance.

6. Eat regularly: Some people find that regular meals help maintain steadier energy levels.

The numan take

Blood sugar management isn’t just about avoiding sugar or chasing perfect “flatline” glucose graphs. It’s about understanding how your body responds, recognising what helps you feel your best, and making small, sustainable changes that support long-term health.

References

1. ^{Eyth E, Zubair M, Naik R. Hemoglobin A1C. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2025.}

2. ^{What is HbA1c? Diabetes UK. 2017. [accessed 4 Nov 2025] Available from: https://www.diabetes.org.uk/about-diabetes/looking-after-diabetes/hba1c}

3. ^{Avner S, Robbins T. A scoping review of glucose spikes in people without diabetes: Comparing insights from grey literature and medical research. Clin Med Insights Endocrinol Diabetes. 2025;18(11795514251381409):11795514251381409.}

4. ^{Ferretti F, Mariani M. Simple vs. Complex carbohydrate dietary patterns and the global overweight and obesity pandemic. Int J Environ Res Public Health. 2017;14(10).}

5. ^{Sharma K, Akre S, Chakole S, Wanjari MB. Stress-induced diabetes: A review. Cureus. 2022;14(9):e29142.} 

6. ^{Brouwer A, van Raalte DH, Rutters F, Elders PJM, Snoek FJ, Beekman ATF, et al. Sleep and HbA1c in patients with type 2 diabetes: Which sleep characteristics matter most? Diabetes Care. 2020;43(1):235–43}

7. ^{Bonora E, Zavaroni I, Alpi O, Pezzarossa A, Dall’Aglio E, Coscelli C, et al. Influence of the menstrual cycle on glucose tolerance and insulin secretion. Am J Obstet Gynecol. 1987;157(1):140–1.}