How to use an HbA1c machine correctly is essential knowledge for anyone managing diabetes at home or in a clinical setting. An HbA1c machine — also known as a point-of-care HbA1c analyser — measures glycated haemoglobin to reflect average blood glucose levels over the preceding two to three months. Used correctly, these devices support effective diabetes monitoring in GP surgeries, pharmacies, and at home. This guide covers how HbA1c machines work, step-by-step instructions for accurate testing, how to interpret results against NHS target ranges, and when to seek advice from your GP or diabetes care team.

What Is an HbA1c Machine and How Does It Work?

An HbA1c machine measures the proportion of glycated haemoglobin in a capillary blood sample using methods such as immunoassay or boronate affinity chromatography, producing a result in mmol/mol within minutes.

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An HbA1c machine — also known as a point-of-care (POC) HbA1c analyser — is a device used to measure glycated haemoglobin in the blood. HbA1c reflects the average blood glucose level over the preceding two to three months, making it a key marker in the ongoing management and monitoring of diabetes.

The underlying principle relies on the fact that glucose binds irreversibly to haemoglobin A within red blood cells. The higher the blood glucose over time, the greater the proportion of haemoglobin that becomes glycated. Machines measure this proportion — expressed in millimoles per mole (mmol/mol), which is the standard unit used in the UK following IFCC alignment.

Point-of-care devices used in GP surgeries, pharmacies, and diabetes clinics — such as the Afinion, Quo-Test, or DCA Vantage (listed as examples only; no endorsement is implied) — typically use a small capillary blood sample obtained via a fingerprick. The sample is applied to a test cartridge or cuvette, and the machine uses methods such as immunoassay or boronate affinity chromatography (the specific method varies by device — refer to the manufacturer's instructions for use) to quantify HbA1c within minutes.

Important: Point-of-care and home-use HbA1c devices are intended for monitoring only. In the UK, a diagnosis of diabetes must be based on a venous blood sample analysed in an accredited laboratory using a quality-assured method, in line with WHO 2011 guidance (as adopted in the UK) and NICE guideline NG28. Do not use a POC or home device result alone to diagnose or rule out diabetes.

Home-use HbA1c kits are available for patients wishing to self-monitor between clinical appointments. Only use devices bearing a CE or UKCA mark, and ensure results are shared with and interpreted by your healthcare team. Home testing complements — but does not replace — laboratory or clinician-supervised testing.

Preparing for an HbA1c Test at Home or in a Clinical Setting

HbA1c testing does not require fasting; however, hands must be washed and dried, cartridges stored per the manufacturer's instructions, expiry dates checked, and sterile lancets used and disposed of safely.

One of the practical advantages of HbA1c testing is that, unlike fasting glucose tests, it does not require the patient to fast beforehand. You can eat and drink normally prior to the test, which makes it more convenient and accessible for routine monitoring.

However, there are several important preparation steps to follow to ensure an accurate result:

• Wash and dry your hands thoroughly before a fingerprick test. Residual food, lotion, or alcohol gel on the skin can contaminate the sample. If alcohol wipes are used to clean the skin, allow the area to dry completely before lancing.

• Store test cartridges strictly as directed by the manufacturer's instructions for use (IFU). Storage requirements vary between devices — some cartridges require refrigeration, whilst others should be kept at a specific room temperature (for example, 15–30°C). Do not assume a single storage range applies to all products. If cartridges have been refrigerated, allow them to reach room temperature before use, as specified in the IFU.

• Check the expiry date of test cartridges before use. Expired consumables are a common source of inaccurate readings.

• Use a new, sterile lancet for each test. Do not re-use lancets. Dispose of used lancets immediately in an approved sharps bin — do not place them in general household waste.

• Infection control: Wash hands before and after the procedure. In clinical settings, wear gloves where indicated by local infection control policy.

In a clinical setting, healthcare professionals must ensure the machine is operated under a local point-of-care testing (POCT) governance framework, in line with MHRA guidance on the management and use of IVD point-of-care test devices. This includes:

• Documented staff training and competency assessment

• Regular internal quality control (IQC) checks

• Participation in an external quality assurance (EQA) scheme, such as UK NEQAS for HbA1c POCT

• Device maintenance logs and records of all QC data

• Use of devices that are CE or UKCA marked for the intended purpose

For home users, read the device's IFU carefully before first use. If you are unsure about any step, your GP surgery, diabetes nurse, or community pharmacist can provide guidance.

Step-by-Step Guide to Using an HbA1c Machine

Allow the device to complete its warm-up cycle, collect a sufficient fingerprick blood sample into the capillary tube, apply it to the cartridge, and record the mmol/mol result — always following the device's specific instructions for use.

While specific steps vary between devices, the following general process applies to most point-of-care HbA1c analysers and home-use kits. Always refer to your device's specific instructions for use (IFU), which take precedence over any general guidance.

Step 1 – Prepare the device Switch on the machine and allow it to complete its self-calibration or warm-up cycle. Insert the test cartridge or cassette as directed, ensuring it clicks or seats firmly into place. Confirm that IQC has been performed and is within acceptable limits before proceeding (clinical settings).

Step 2 – Prepare the fingerprick site Wash and dry your hands. In clinical settings, wear gloves where required by local policy. Using a new, sterile lancet device, prick the side of a fingertip (the index, middle, or ring finger is recommended). Avoid the very tip of the finger, which is more sensitive. Wipe away the first drop of blood with a clean tissue.

Step 3 – Collect the blood sample Allow a second drop of blood to form. Using the supplied capillary tube or pipette, collect the required volume of blood as specified in the IFU — this varies between devices. Avoid squeezing the finger excessively, as this can dilute the sample with tissue fluid. If the sample appears underfilled or contains air bubbles, discard it and repeat the collection; do not proceed with an inadequate sample, as this can produce a falsely low or error result.

Step 4 – Apply the sample Apply the collected blood to the designated area of the test cartridge or directly into the machine's sample port, following the manufacturer's instructions precisely.

Step 5 – Wait for the result Most POC devices produce a result within 3 to 10 minutes. Do not move or disturb the machine during analysis.

Step 6 – Record and interpret the result Note the result displayed in mmol/mol (UK standard). Record the date, time, and reading. In clinical settings, document the result in the patient record and log it alongside QC data in line with your organisation's POCT policy.

Step 7 – Safe disposal Dispose of the used lancet immediately in a sharps bin. Dispose of the used cartridge and any blood-contaminated materials in line with local clinical waste or household sharps disposal guidance.

Understanding Your HbA1c Results and NHS Target Ranges

In the UK, an HbA1c below 42 mmol/mol is normal, 42–47 mmol/mol indicates non-diabetic hyperglycaemia, and 48 mmol/mol or above indicates diabetes when confirmed by a laboratory venous sample.

In the UK, HbA1c results are reported in mmol/mol in line with IFCC standardisation. Understanding what your result means is essential for informed self-management and clinical decision-making.

NHS and NICE reference ranges include:

• Below 42 mmol/mol — Normal range; diabetes is unlikely

• 42–47 mmol/mol — Non-diabetic hyperglycaemia (sometimes called prediabetes); indicates increased risk of developing type 2 diabetes

• 48 mmol/mol or above — Indicates diabetes (when confirmed on a second laboratory test in asymptomatic individuals, per NICE guideline NG28 and WHO 2011 guidance)

Important diagnostic limitations — HbA1c should not be used for diagnosis in the following circumstances:

• Pregnancy (including suspected gestational diabetes — alternative tests are used; see NICE NG3)

• Suspected type 1 diabetes (clinical diagnosis; HbA1c alone is insufficient)

• Children and young people

• Acute illness (results may be unreliable)

• Haemolytic anaemia, iron deficiency anaemia, or haemoglobin variants (e.g., HbS, HbC) — these can cause falsely low or falsely high results

• Recent blood transfusion — results will be unreliable

In these circumstances, alternative markers such as fructosamine, or alternative diagnostic tests (fasting plasma glucose or oral glucose tolerance test), may be considered by your clinical team.

For people already diagnosed with diabetes, NICE recommends the following treatment targets:

• Type 2 diabetes (managed with lifestyle or non-hypoglycaemic drugs): Target HbA1c of 48 mmol/mol

• Type 2 diabetes (managed with drugs that carry a hypoglycaemia risk, e.g., sulphonylureas or insulin): Target of 53 mmol/mol

• Type 1 diabetes: NICE (NG17) recommends aiming for 48 mmol/mol where safely achievable

These targets are a guide and should be individualised in discussion with your diabetes care team, taking into account factors such as hypoglycaemia risk, frailty, comorbidities, and personal circumstances. Always discuss your result in the context of your overall health with a qualified healthcare professional.

Common Errors and How to Ensure Accurate Readings

The most frequent errors are insufficient blood volume, air bubbles in the capillary, contaminated samples, and expired or improperly stored cartridges — all of which can produce falsely low results or error readings.

Even with straightforward devices, errors in technique or equipment handling can lead to inaccurate HbA1c readings. Being aware of common pitfalls helps ensure reliable results.

Common sources of error include:

• Insufficient blood volume: Underfilling the capillary tube is one of the most frequent mistakes. An inadequate sample can produce a falsely low result or an error reading. Always collect the full volume specified in the IFU.

• Air bubbles in the capillary: These can displace blood and reduce sample volume. Allow blood to fill the capillary by capillary action rather than forcing it.

• Contaminated sample: Residual alcohol from hand sanitiser or skin-preparation wipes can interfere with the sample. Always allow the skin to dry fully before lancing.

• Expired or improperly stored cartridges: Cartridges exposed to incorrect temperatures, humidity, or used past their expiry date may yield unreliable results. Follow the IFU for storage conditions precisely.

• Failure to perform quality control checks: In clinical settings, skipping IQC testing means errors may go undetected. Follow your organisation's POCT policy.

• Haemoglobin variants and haematocrit: Some assay methods are affected by haemoglobin variants (e.g., HbS, HbC) or abnormal haematocrit. Check the IFU for your specific device to understand its known interferences, and consider laboratory confirmation when a haemoglobinopathy or significant anaemia is suspected.

• Patient-specific factors: As noted above, haematological conditions can affect HbA1c independently of blood glucose levels.

To maximise accuracy:

• Calibrate and perform IQC on the device regularly according to the manufacturer's schedule and local POCT policy

• Use only compatible, in-date consumables from the approved supplier

• Document all results, QC data, and maintenance records in line with clinical governance requirements

• Periodically cross-check POC results with laboratory HbA1c as part of your POCT quality assurance programme, and participate in an EQA scheme such as UK NEQAS

For home users, if a result seems unexpectedly high or low compared to your recent readings or symptoms, repeat the test using a fresh cartridge and contact your GP or diabetes nurse for confirmation using a laboratory sample.

When to Seek Advice from Your GP or Diabetes Care Team

Seek urgent emergency care for suspected severe hypoglycaemia or DKA; contact your GP promptly if your HbA1c is 48 mmol/mol or above without a prior diagnosis, or if results change significantly.

HbA1c machines — whether used at home or in a clinical setting — provide valuable monitoring information, but they are not a substitute for professional medical assessment. Knowing when to seek help is an important aspect of safe diabetes management.

Call 999 or go to your nearest emergency department immediately if you or someone else:

• Has lost consciousness, is having a seizure, or cannot be roused — this may indicate severe hypoglycaemia

• Has symptoms that may suggest diabetic ketoacidosis (DKA) or hyperosmolar hyperglycaemic state (HHS): abdominal pain, persistent vomiting, drowsiness, rapid or laboured breathing, or high ketone levels

These are medical emergencies requiring urgent same-day assessment or emergency care.

Contact your GP or diabetes care team promptly if:

• Your HbA1c result is 48 mmol/mol or above and you have not previously been diagnosed with diabetes — a confirmatory laboratory test will be needed

• Your result has risen significantly since your last reading, particularly if you have made no changes to diet, activity, or medication

• Your result is unexpectedly low and you are experiencing symptoms of hypoglycaemia (shakiness, sweating, or confusion)

• You are experiencing symptoms such as excessive thirst, frequent urination, unexplained weight loss, or fatigue, regardless of your HbA1c reading

• You are pregnant or planning a pregnancy — contact your maternity or diabetes antenatal team promptly. Tighter glycaemic targets apply in pregnancy, more frequent monitoring is recommended (NICE NG3), and HbA1c is not used to diagnose gestational diabetes

• You suspect your device may be malfunctioning or producing inconsistent results

How often should HbA1c be measured? NICE recommends measuring HbA1c every 3 months when treatment has recently changed or targets are not being met, and every 6 months when diabetes is stable and targets are achieved. Your diabetes care team will advise on the frequency appropriate for your individual circumstances.

It is also worth noting that HbA1c alone does not capture day-to-day glucose variability or episodes of hypoglycaemia. Your diabetes care team may recommend complementary monitoring — such as self-monitored blood glucose (SMBG) or continuous glucose monitoring (CGM) — depending on your treatment regimen and individual circumstances.

Regular structured reviews with your GP or diabetes nurse remain the cornerstone of safe, effective diabetes management in the UK.

Frequently Asked Questions