First things first, the terms ‘blood sugar’ and ‘blood glucose’ basically mean the same thing and they are often used interchangeably. To understand what they are, we need to talk about food!

There are three types of carbohydrates in the food we eat: starch, fibre, and sugars. You might instantly think of sugar in the diet as being ‘bad’, but that’s not the whole story. We all need to consume certain forms of sugar because the body turns it into fuel that provides us with energy. From the simplest of processes like breathing to the most demanding and energy-zapping—running a marathon, for instance—they all rely on sugar. 

When you eat carbohydrates, the digestive system breaks some of them down into sugar, which enters the bloodstream. In response, the pancreas makes the hormone insulin, and that prompts the body’s cells to absorb the blood sugar and use it as fuel. 

If you have type 2 diabetes, either your pancreas can’t make enough insulin or the insulin it produces doesn’t work properly.[1] So, while your body still turns carbohydrates into glucose, the insulin can’t function as it should. Body cells don’t absorb the glucose and instead, it accumulates in the blood leaving you with high blood sugar levels—the hallmark of type 2 diabetes. 

Why is blood sugar important?

For people with newly diagnosed type 2 diabetes, understanding blood sugar is crucial because managing it can go a long way to preventing diabetes complications.[2, 3] The first step is getting to grips with your own blood glucose normal range and keeping it within target.

Blood sugar levels specifically refer to the concentration of glucose in the blood. They are assessed differently around the world: levels are sometimes notated as mg/dL (milligrams per decilitre), a ratio of weight to volume commonly used in the US. But in the UK, the standard is to measure the number of glucose molecules per litre of blood (mmol/L)—so that’s the magic number to look out for. 

Everyone’s blood glucose levels fluctuate throughout the day, reaching their lowest when you’ve not eaten for a while and their highest shortly after a meal. So, it makes sense that your sugar levels before and soon after food are most indicative of your blood glucose control and diabetes management. 

National guidelines state the following target ranges for people with diabetes:[4]

Before meals: 4 to 7 mmol/L (also for people with type 1 diabetes)

90 minutes or more after meals: Less than 8.5mmol/L

‍Measuring blood sugar

Keeping a close check on your blood glucose levels can help you to manage your type 2 diabetes in several ways. It can be useful in getting to grips with your condition, especially if you’re newly diagnosed with type 2 diabetes.

Regular monitoring can help you avoid your sugar levels getting too high, known as hyperglycaemia or a hyper, or too low, known as hypoglycaemia or a hypo. These are potentially dangerous effects of diabetes that can lead to serious complications and threaten your long-term health.

If you take certain medication, you’ll need to measure your blood sugar levels routinely every day; doing so will help determine whether you need to adjust your meds or their doses. Don’t make any changes to your medication without first speaking to your diabetes specialist or healthcare professional. 

There are different ways to check your blood glucose levels, but they don’t all measure the same thing, so you need to know exactly what you’re testing and what the results mean.

Ways of checking your blood sugar

The most basic way to measure your blood glucose levels is with a finger prick test. Using a small device that holds a tiny needle called a lancet, you pierce the skin on a fingertip and collect the drop of blood on a testing strip, which is attached to a blood test meter. Within a few minutes, the meter displays a reading—this is your blood sugar level at that moment in time. 

People with type 2 diabetes are increasingly using a blood glucose monitor to keep their levels in check. There are two types—a flash glucose monitor and a continuous glucose monitor (CGM)—and neither requires needles and finger prick testing. 

Both types of blood glucose monitor use a small sensor worn on the skin (usually the upper arm) all the time, which reads your glucose levels and transmits the reading to your smartphone or monitoring device. 

A CGM does this automatically, whereas you need to scan your sensor with a flash device to get the reading. 

‍Blood glucose over time

Both types of blood glucose monitor allow you to see your blood sugar levels at a glance throughout the day and night, which can give you a broader picture of your diabetes, help identify patterns in your levels, and help you stay within your blood glucose normal range for longer.

Blood glucose monitors are not as accurate as finger-prick testing because they measure sugar in the fluid surrounding the cells rather than in the blood itself. This means the reading displayed isn’t in real-time but represents your sugar levels around 15 minutes earlier. 

The difference between your actual blood sugar level and your blood glucose monitor reading can be fairly great around mealtimes and when exercising. So, it’s worth checking your levels with the occasional finger prick test too.

As part of your long-term diabetes care plan, you’ll periodically have an HbA1c blood test to gauge your average blood sugar level over a period of three months. Signalling how well managed your blood glucose is over time, this important test can help you and your healthcare team spot trends and prevent your diabetes from spinning out of control.

The unit of measurement for HbA1c is millimoles (mmol) per mole (mol). Your healthcare team can help you understand what that means, but the magic number you need to aim for if you have diabetes is 48mmol/mol (6.5%) or lower.[5]

If you take certain diabetes medication, it’s likely your target will be slightly higher, at 53mmol/mol (7.0%).[6]

‍What affects blood glucose levels?

It’s not just what you eat and when that has an effect on your blood sugar levels. Whether or not you take diabetes medication, and what type of medication, directly impacts your blood sugar so any adjustments in your dose or timings can also trigger fluctuations. Other types of medication unrelated to your diabetes can also send your levels up or down.

Your state of health is linked with blood glucose control, too. If you’re stressed, have a virus or illness, or make changes to your diet or exercise patterns—drinking more alcohol than normal or dieting to lose weight, for instance—you might notice a knock-on effect on your normal blood glucose levels. 

And for women, periods, pregnancy, and menopause can disrupt normal blood glucose levels, so bear these factors in mind when measuring and recording your readings.[7] 

‍The takeaway

The ins and outs of blood sugar and what your levels mean can be tricky to get your head around. But with support from your healthcare team and armed with a bit of knowledge, you can become an expert in your condition, and stay healthy and in control.