Monitoring Your Glucose For Diabetes

Introduction

Diabetes is a chronic condition characterised by high levels of blood glucose. Data from Diabetes UK in 2023 showed at least 4.3 million UK citizens have diabetes, with another 850,000 yet to be diagnosed. Fluctuations in blood glucose outside of a healthy range can lead to symptoms like fatigue and weight loss, or severe complications like cardiovascular disease. Longer and more frequent periods outside this range can amplify symptoms, so quickly identifying high or low blood glucose levels is crucial. By regularly monitoring blood glucose levels, patients can track changes in the disease, identify trends, and see the effect of lifestyle on glucose levels. Patients and their healthcare providers can then make informed decisions to improve disease management. In this article, we will explore the fundamentals and importance of monitoring blood glucose for diabetes, the tools available, and practical tips for monitoring to manage diabetes symptoms best.

Understanding diabetes and blood glucose

Diabetes overview

Diabetes is the name for a group of diseases characterised by high blood glucose. The most common variants are type 1 (T1DM) and type 2 diabetes mellitus (T2DM), but there are other less common types like gestational diabetes (see here for more information). Different diabetes subtypes have different causes; those with T1DM do not produce enough of the hormone insulin, whereas T2DM patients don’t respond as well to insulin. However, the common feature is high blood glucose, which can lead to various symptoms. But what is glucose and why is it important for our bodies?  

Glucose in health and diabetes

Glucose is a type of sugar and the main source of energy for every cell in our bodies. When we have a meal, our food is broken down into its constituent molecules like glucose, which is then absorbed into the blood to be transported around the body. The pancreas detects the increased blood glucose and releases insulin. Insulin signals to our cells to take up glucose, and either use it or store it to provide energy until we have our next meal.¹

In patients with T1DM and T2DM, the insulin system does nott work properly, so glucose isn’t taken up from the blood efficiently. This results in high blood glucose, or ‘hyperglycaemia’, leading to symptoms like dehydration, weight loss, fatigue, confusion, mood changes, and a higher risk of infections.² Long-term hyperglycaemia can lead to serious complications including nerve and cardiovascular damage.³

T1DM patients control their blood glucose with medication e.g. insulin injections. However, factors like physical activity, eating meals later than usual, or too much alcohol can mean needing less insulin than expected. Taking too much insulin in these situations can cause very low blood sugar or ‘hypoglycaemia’, leading to headaches, increased appetite, anxiousness, confusion and cold sweats.^1,2

The importance of blood glucose monitoring

As we can see, blood glucose is like a seesaw, finding the ideal spot between hyper and hypoglycemia. The body is normally very good at this balancing act, but diabetes patients have to manage it themselves to stay in a healthy range and reduce symptoms. To best manage blood glucose, patients must first know what their current levels are. This allows patients and healthcare professionals to make informed decisions. In the short term, the patient may need medication, food or behavioural change (e.g. pausing exercise) to bring glucose under control. In the long term, they may need a different medication or dosage. This is where blood glucose monitoring comes in. 

Tools for monitoring blood glucose

There are two main methods to monitor glucose at home; a blood glucose monitor (BGM) or a continuous glucose monitor (CGM). There are other tests used by healthcare professionals like venous blood tests and HbA1C tests, but these can’t be done at home. You can read more about other tests here.¹

Blood glucose monitors (BGMs)

BGMs, also known as finger-prick, finger-stick or capillary glucose tests, measure blood glucose directly from a blood sample. The test is made up of three parts: a lancet, the electronic reader (a glucometer) and test strips. The user pricks their finger using a lancet, adds a small amount of blood to the test strip then inserts it into a glucometer (see here for a step-by-step guide with user advice). The test strip uses a chemical reaction to generate an electrical signal proportional to the amount of glucose. The glucometer detects and translates the size of this signal into a blood glucose level.¹

Modern glucometers only need a very small amount of blood and have Bluetooth capabilities to share data with smartphone apps. This allows patients and healthcare providers to see current blood glucose and how it responds to medication, diet or lifestyle.¹ If a glucometer does not automatically log readings, patients should manually record them for future reference by their healthcare provider.

Continuous glucose monitors (CGMs)

CGMs are small patches that stick to your skin to continually monitor glucose levels. Unlike a lancet, the sensor is small and doesn’t pierce skin far enough to enter a blood vessel. Instead, it measures blood glucose from the interstitial fluid; fluid that leaks out of our blood vessels into the space between cells.

CGMs come in two types, real-time CGM (rtCGM) and intermittently scanned CGM (isCGM), also known as a flash monitor.⁴ An isCGM automatically checks blood glucose roughly every 15 minutes but needs to be scanned by a smartphone or dedicated device to store data. In contrast, rtCGMs automatically scan and send data every 1-5 minutes.⁴ rtCGMs can also connect directly to insulin pumps, automatically administering varying doses of insulin depending on blood glucose readings. This is known as a ‘hybrid closed-loop system’ or ‘artificial pancreas’.^1,4 The automatic nature and higher frequency mean rtCGMs are supplanting isCGMs.

The more frequent glucose readings offered by CGMs provide useful features over BGMs. Patients can get a more regular idea of their blood glucose at all times of the day, including while they sleep, to better see trends over time. The paired smartphone app or device can tell patients if they’re in a healthy range of blood glucose and get alarms if this changes. Frequent readings allow us to create a useful metric; time in range (TIR). TIR is both intuitive for patients, and a low TIR correlates well with higher symptom frequency and severity.⁵

Choosing the right monitoring tool for you

There are advantages and disadvantages for each monitor. Discuss with your healthcare provider if one or more are appropriate for you.

Using blood glucose readings

Understanding target ranges

Once a patient has read their blood glucose it should be compared to example values (see Table 2) to determine if it is at a healthy point, or if the patient is hyper/ hypoglycemia. The actual ranges for a specific patient will depend on factors like age, duration of diabetes, cardiovascular disease and even the opinions of different organisations. Patients should consult a healthcare professional to find out what is appropriate for them. Different patients use either mmol/L or mg/dL to measure their glucose levels so we have included both in Table 2. 

When to monitor blood glucose

NICE guidelines recommend that T1DM patients use CGM as frequently as is practical or use BGM to take readings at least four times per day (before meals and before sleep). However, measurements can be taken as often as 10 times per day e.g. two hours after a meal or in situations that can greatly alter glucose such as during exercise, stress or illness. In general, T2DM patients don’t need to monitor glucose unless they’re taking insulin, pregnant or planning pregnancy.⁴ Patients should consult a healthcare professional for specific guidance, as well as actions to take when outside their healthy range.

Conclusion

Regular glucose monitoring is the best thing diabetes patients can do to help manage their blood glucose. Two main tools are available to achieve this: blood glucose monitors (BGMs) and continuous glucose monitors (CGMs). BGMs require taking blood samples to directly test glucose levels, whereas CGMs continually measure interstitial fluid glucose using a skin sensor. Both methods have advantages and disadvantages, but the automatic and more regular readings from CGM make it a powerful tool. NICE guidelines recommend taking measurements four to ten times per day for T1DM patients. Recording blood glucose readings and comparing them to the healthy glucose range discussed with a healthcare professional allows patients to take informed actions to manage their blood glucose levels and by extension their symptoms.