How to Take Blood Glucose: A Step-by-Step Guide

How to take blood glucose readings accurately is an essential skill for anyone managing diabetes at home. Self-monitoring of blood glucose gives you and your clinical team real-time information about how your blood sugar responds to food, activity, illness and medication. Whether you use a traditional fingertip meter or a continuous glucose monitor, understanding the correct technique, equipment and target ranges helps you make safer, more informed decisions about your care. This guide covers everything you need to know, from choosing the right equipment to interpreting your results and knowing when to seek medical advice.

How do you check your blood glucose at home?

You check blood glucose at home using a handheld meter that measures glucose in a fingertip blood drop. NICE supports self-monitoring for type 1 diabetes and for type 2 diabetes managed with insulin or medicines that carry a hypoglycaemia risk.

You check your blood glucose at home by using a small handheld device called a blood glucose meter, which measures the concentration of glucose in a drop of blood obtained from a fingertip prick. This process is known as self-monitoring of blood glucose (SMBG) and is a cornerstone of diabetes management for many people living with type 1 or type 2 diabetes. It gives you and your clinical team real-time information about how your blood sugar responds to food, physical activity, illness and medication.

NICE guidance (NG17 for type 1 diabetes and NG28 for type 2 diabetes) supports self-monitoring for people with type 1 diabetes and for those with type 2 diabetes who use insulin or certain other medicines that carry a risk of hypoglycaemia.^[1][2] Your GP or diabetes nurse will advise whether routine home monitoring is appropriate for your situation, as it is not universally recommended for everyone with type 2 diabetes managed by diet alone or by medicines that do not lower glucose independently.^[3][4]

Some people are now offered continuous glucose monitors (CGMs), which use a small sensor worn on the skin to measure glucose in the fluid beneath the skin every few minutes. There are two main types available on the NHS: intermittently scanned CGM (sometimes called flash glucose monitoring) and real-time CGM.^[5] Eligibility is determined by your local diabetes service. CGMs are increasingly available for eligible patients, particularly those with type 1 diabetes. However, fingertip testing with a meter remains widely used and is the focus of this guide. If you are unsure which method is right for you, speak to your GP or diabetes care team.

What equipment do you need to test your blood sugar?

You need a blood glucose meter, compatible test strips, a lancing device, single-use lancets and an approved sharps bin. Test strips are available on NHS prescription for eligible patients.

To test your blood sugar at home you need a blood glucose meter, compatible test strips, a lancing device, lancets, and a means of safely disposing of sharps. Each component plays a specific role in producing a reliable result, and using mismatched or expired supplies is one of the most common causes of inaccurate readings.

Here is a summary of the key items:

• Blood glucose meter: A small electronic device that reads the glucose level in your blood sample. Many meters are available; your diabetes team or pharmacist can advise on a suitable model.

• Test strips: Single-use strips that are inserted into the meter. They must be compatible with your specific meter model and must not be used beyond their expiry date or after the vial has been open for longer than the manufacturer recommends. Open-vial lifespan varies by brand and strip type, so always follow the instructions for use supplied with your strips.

• Lancing device and lancets: The lancing device holds a lancet (a very fine needle) and is used to prick the fingertip. Lancets are single-use and should be changed with every test to minimise discomfort and infection risk. Do not share your lancing device with anyone else, as this carries a risk of blood-borne infection.

• Sharps bin: Used lancets must be disposed of in an approved sharps container. Test strips should be disposed of in accordance with your local council or NHS guidance, which in many areas permits strips to go in household waste while lancets require a sharps bin. Your GP surgery or local pharmacy can advise on how to obtain and return sharps containers safely.

• Record book or app: Keeping a log of your readings, along with the time, what you ate and any relevant activity, helps your clinical team interpret patterns over time.

Test strips are available on NHS prescription for eligible patients. Your GP or diabetes nurse can confirm whether you qualify and how many strips are appropriate for your monitoring frequency.

How to take a blood glucose reading step by step

Wash and dry your hands, insert a fresh strip, prick the side of a fingertip, apply the blood drop to the strip, then record the result and dispose of the lancet in a sharps bin.

Taking a blood glucose reading involves a straightforward sequence of steps that becomes quick and routine with practice. Following each step carefully helps ensure the result is accurate and that the process is as comfortable as possible. Always refer to the instructions for use supplied with your specific meter and lancing device, as details may vary between models.

Step 1: Wash and dry your hands. Wash with warm water and soap, then dry thoroughly. Residual food, hand cream or moisture on the fingertip can affect the reading. Avoid using alcohol wipes on the fingertip immediately before testing where possible; if you do use one, allow the skin to dry completely before lancing.

Step 2: Prepare your equipment. Insert a new test strip into the meter. The meter will usually switch on automatically. Check that the code on the strip vial matches any code displayed on the meter, if your device requires this. Also check that the meter's date and time are set correctly so that your log is accurate.

Step 3: Load and set the lancing device. Insert a fresh lancet, set the depth to a comfortable level (deeper settings may be needed for thicker skin), and cock the device ready to fire.

Step 4: Prick the side of a fingertip. The sides of the fingertip are less sensitive than the pad. Rotate which finger and which side you use to avoid soreness. Press the lancing device firmly against the skin and release.

Step 5: Obtain a blood drop. Gently squeeze the finger from the base towards the tip to encourage a small drop of blood. Avoid squeezing hard, as this can dilute the sample with tissue fluid.

Step 6: Apply blood to the strip. Touch the blood drop to the correct end of the test strip as directed by your meter's instructions. The meter will count down and display your result.

Step 7: Record and dispose safely. Note the reading in your log, then place the used lancet in your sharps bin. Discard the test strip in accordance with your local council or NHS guidance.

What do your blood glucose results actually mean?

A pre-meal reading of 4.0 to 7.0 mmol/L is a general target for many adults with diabetes; below 4.0 mmol/L indicates hypoglycaemia requiring immediate treatment. Your diabetes care team will set your personalised targets.

Blood glucose is measured in millimoles per litre (mmol/L) in the UK, and what constitutes a normal or target range depends on whether you have diabetes, when you last ate, and your individual treatment plan. Your diabetes care team will set personalised targets for you, and these should always take precedence over general reference ranges.

As a general guide, NICE (NG17 and NG28) and Diabetes UK publish the following approximate reference values for adults with diabetes:

• Before meals (fasting or pre-meal): 4.0 to 7.0 mmol/L is a commonly cited target for many people with type 1 or type 2 diabetes, though individual targets vary.

• Two hours after meals: Generally below 8.5 to 9.0 mmol/L, depending on the guidance your team follows.

• Hypoglycaemia (low blood sugar): A reading below 4.0 mmol/L is considered low and requires prompt action.

• Hyperglycaemia (high blood sugar): Persistently elevated readings above your agreed target should be discussed with your GP or diabetes nurse.

If your reading is below 4.0 mmol/L and you are able to swallow safely, treat with a fast-acting carbohydrate (for example, 15 to 20 g of glucose, such as glucose tablets or a small glass of fruit juice), then retest after 10 to 15 minutes. Once your reading has recovered, follow with a longer-acting carbohydrate such as a biscuit or your next meal if it is due. If someone with diabetes is unconscious, having a seizure, or unable to swallow, do not give anything by mouth. Call 999 immediately.

For people with type 1 diabetes or others at risk of diabetic ketoacidosis (DKA), if your blood glucose is persistently high or you feel unwell, check your blood ketones if you have a ketone meter. Raised ketones alongside high glucose or symptoms such as nausea, vomiting, abdominal pain or rapid breathing require urgent medical attention. Call 999 or go to your nearest emergency department. Your diabetes team should provide you with a sick-day rules plan that sets out when to check ketones and when to seek help.

A single reading is rarely cause for alarm on its own. Patterns over days and weeks are far more informative. Your HbA1c blood test, taken at your GP surgery every 3 to 6 months, gives a longer-term picture of average glucose control over approximately 3 months and complements your home readings.^[11]

If you experience symptoms of hypoglycaemia (shakiness, sweating, confusion, palpitations) or hyperglycaemia (excessive thirst, frequent urination, fatigue), check your glucose level and follow your care plan. Contact your GP if readings are consistently outside your agreed range, or call NHS 111 if you are unsure what to do.

When should you be testing your blood sugar levels?

Testing frequency depends on your diabetes type and treatment; NICE NG17 recommends at least 4 tests daily for type 1 diabetes, while routine testing is generally not recommended for type 2 diabetes managed without hypoglycaemia-risk medicines.

How often and when you should test your blood sugar depends on your type of diabetes, your treatment regimen and any specific advice from your diabetes care team. There is no single schedule that applies to everyone, and testing frequency should be agreed with your GP or diabetes nurse rather than decided independently.

For people with type 1 diabetes, NICE NG17 recommends testing at least 4 times daily, including before each meal and before bed.^[2][1] Testing may also be needed before and after exercise, when driving, during illness, or whenever hypoglycaemia is suspected. Those using CGMs may test less frequently by fingertip but should still confirm CGM readings with a fingertip test in certain situations, such as when symptoms do not match the sensor reading.

For people with type 2 diabetes using insulin, testing before meals and at bedtime is common practice. Those on sulphonylureas (medicines that stimulate insulin release) may also be advised to test, particularly if they drive or operate machinery, because of the hypoglycaemia risk. For people managing type 2 diabetes with diet alone or with medicines that do not cause hypoglycaemia, routine home testing is generally not recommended by NICE NG28 unless there is a specific clinical reason.

Driving: If you take insulin or medicines that can cause hypoglycaemia, the DVLA requires you to check your blood glucose before driving and at intervals of approximately every 2 hours on longer journeys.^[9][10] If your reading is below 5.0 mmol/L, do not drive. Refer to the official DVLA guidance on diabetes and driving for the full requirements, as these are a legal obligation.

Additional testing is often advisable in the following circumstances:

• During illness (sick-day rules apply, and your team should provide guidance on when to increase testing and when to check ketones)

• When starting a new medicine or changing a dose

• Before and after strenuous physical activity

• During pregnancy, where tighter glucose control is essential and closer monitoring is usually directed by your specialist antenatal diabetes team

Always follow the personalised advice of your diabetes care team, and contact your GP if your testing needs change.

Tips for getting accurate readings and avoiding common mistakes

Always wash and dry hands before testing, use unexpired strips stored correctly, and use a fresh lancet every time. Squeezing the finger too hard or skipping meter calibration are common causes of inaccurate readings.

Accurate blood glucose readings depend on consistent technique, well-maintained equipment and awareness of the factors that can cause misleading results. Even small errors in method can produce readings that are several mmol/L away from your true glucose level, which could lead to unnecessary concern or, more seriously, an inappropriate treatment decision.

Common mistakes to avoid:

• Not washing hands before testing. Traces of fruit juice, sugary food or hand cream on the fingertip can falsely elevate readings. Always wash and dry hands thoroughly.

• Using expired or incorrectly stored test strips. Strips exposed to heat, humidity or air beyond the recommended period give unreliable results. Store strips in their original sealed vial, away from direct sunlight and extremes of temperature, and follow the manufacturer's instructions for how long an opened vial remains usable.

• Squeezing the finger too hard. Excessive pressure dilutes the blood sample with interstitial fluid, which can lower the apparent glucose reading.

• Reusing lancets. Blunt lancets cause more discomfort and may not produce an adequate blood sample. Use a fresh lancet every time, and do not share your lancing device.

• Not calibrating or coding the meter. Some meters require a code to be entered when a new vial of strips is opened. Skipping this step can introduce systematic errors.

• Testing from a cold hand. Poor circulation to the fingertips in cold conditions can make it harder to obtain a sample. Warming your hands beforehand helps.

• Interfering substances. Some meters and strip types can be affected by certain substances, including high-dose vitamin C, or by extremes of haematocrit. Check your meter's instructions for use for a list of known interferences specific to your device.

Keep your meter clean and follow the manufacturer's guidance on quality control testing. Control solution for quality checks may not be included with every meter; if yours did not come with one, contact the manufacturer or ask your pharmacist. If your readings seem inconsistent with how you feel, repeat the test with a fresh strip. If you remain concerned, contact your GP or diabetes nurse for a review of your technique and equipment. Suspected faults with a medical device can be reported to the MHRA via the Yellow Card scheme at yellowcard.^[12]mhra.gov.uk.

Scientific References

1. Type 1 diabetes in adults: diagnosis and management (NG17) – Recommendations.
2. Type 1 diabetes in adults: diagnosis and management (NG17) – Checking your own blood glucose and target levels (patient information).
3. Type 2 diabetes in adults: management (NG28) – Blood glucose management chapter.
4. Type 2 diabetes in adults: management (NG28) – Full guideline.
5. Continuous glucose monitoring and hybrid closed loop for diabetes.
6. Hypoglycaemia – Treatment summaries.
7. Low blood sugar (hypoglycaemia).
8. Diabetes mellitus, diagnostic and monitoring devices.
9. Diabetes mellitus: assessing fitness to drive.
10. Diabetes and driving.
11. HbA1c – Type 1 diabetes in adults: patient information (NG17).
12. The Yellow Card scheme: guidance for healthcare professionals, patients and the public.

Frequently Asked Questions