Hasil HbA1c dapat menurun akibat berbagai faktor — mulai dari perbaikan gaya hidup dan pengobatan diabetes hingga kondisi medis yang memengaruhi sel darah merah. HbA1c, atau haemoglobin terglikasi, mencerminkan rata-rata kadar glukosa darah selama dua hingga tiga bulan terakhir dan merupakan alat penting dalam pengelolaan diabetes. Namun, penurunan hasil HbA1c tidak selalu berarti kontrol gula darah membaik. Memahami penyebab di balik perubahan hasil ini sangat penting agar pasien dan klinisi dapat mengambil keputusan yang tepat dan aman.
Summary: Hasil HbA1c dapat menurun akibat perbaikan kontrol gula darah melalui obat-obatan atau gaya hidup, tetapi juga akibat kondisi medis seperti anemia hemolitik, penyakit ginjal kronis, kehamilan, atau transfusi darah yang memengaruhi akurasi pengukuran.
- HbA1c mencerminkan rata-rata kadar glukosa darah selama 8–12 minggu terakhir, diukur dalam mmol/mol di UK.
- Kondisi yang memperpendek masa hidup sel darah merah — seperti anemia hemolitik, hemoglobinopati, atau transfusi darah — dapat menyebabkan HbA1c tampak rendah secara artifisial.
- Obat-obatan diabetes seperti metformin, SGLT-2 inhibitor, GLP-1 receptor agonist, dan insulin dapat menurunkan HbA1c secara nyata bila digunakan sesuai panduan NICE NG28.
- Perubahan gaya hidup termasuk diet rendah karbohidrat, aktivitas fisik rutin, dan penurunan berat badan terbukti menurunkan HbA1c pada penderita diabetes tipe 2.
- HbA1c yang turun tanpa penjelasan jelas — tanpa perubahan obat, diet, atau berat badan — memerlukan evaluasi klinis lebih lanjut untuk menyingkirkan penyebab medis yang mendasarinya.
- Pada kondisi tertentu seperti kehamilan atau penyakit ginjal lanjut, HbA1c tidak dapat diandalkan dan penanda alternatif seperti fruktosamin atau pemantauan glukosa mandiri lebih dianjurkan.
Table of Contents
- What Is HbA1c and What Do Your Results Mean?
- Common Medical Causes of a Lower HbA1c Reading
- Medications and Treatments That Can Reduce HbA1c Levels
- Lifestyle Factors That May Affect Your HbA1c Result
- When a Falling HbA1c May Require Further Investigation
- When to Speak to Your GP About Your HbA1c Results
- Frequently Asked Questions
What Is HbA1c and What Do Your Results Mean?
HbA1c is a blood test measuring average blood glucose over 8–12 weeks; in the UK, a result of 48 mmol/mol or above may indicate type 2 diabetes, while results can be falsely low due to conditions affecting red blood cell turnover.
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HbA1c, or glycated haemoglobin, is a blood test that reflects your average blood glucose levels over the preceding two to three months. When glucose circulates in the bloodstream, it binds to haemoglobin — the protein found inside red blood cells — forming glycated haemoglobin. Because red blood cells have a typical lifespan of approximately 120 days, the HbA1c result provides a reliable snapshot of longer-term blood sugar control — broadly reflecting the last 8–12 weeks — rather than a single moment in time.
In the UK, HbA1c is measured in millimoles per mole (mmol/mol). According to NICE guidelines (NG28):
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Below 42 mmol/mol is considered normal
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42–47 mmol/mol indicates non-diabetic hyperglycaemia (NDH) — sometimes referred to as prediabetes — representing an increased risk of developing type 2 diabetes
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48 mmol/mol or above may be used to diagnose type 2 diabetes in appropriate clinical contexts
Importantly, HbA1c is not suitable for diagnosing diabetes in all situations. NICE advises that it should not be used to diagnose type 1 diabetes, in children and young people, during pregnancy or within two months of giving birth, in people with acute illness, or where conditions affecting red blood cell turnover are present (such as haemoglobinopathies, haemolytic anaemia, or recent blood transfusion). In people without symptoms, a diagnosis of type 2 diabetes should be confirmed with a repeat HbA1c test on a separate occasion before a diagnosis is made.
For people already diagnosed with diabetes, a falling HbA1c is often a positive sign, suggesting improved blood glucose management. However, a declining result is not always straightforwardly good news. In some circumstances, a lower HbA1c may reflect underlying medical conditions, changes in red blood cell turnover, or other physiological factors that can distort the measurement — making it appear artificially low rather than reflecting genuine improvements in glycaemic control.
Understanding what drives a change in your HbA1c result is therefore important for both patients and clinicians. A result should always be interpreted in the context of your overall health, symptoms, and any recent changes to your medication or lifestyle.
Key references: NICE NG28 (Type 2 diabetes in adults: management); NHS HbA1c test information.
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Common Medical Causes of a Lower HbA1c Reading
Haemolytic anaemia, haemoglobinopathies, chronic kidney disease, recent blood transfusion, and pregnancy can all cause a falsely low HbA1c by shortening red blood cell lifespan and reducing glycated haemoglobin accumulation.
Several medical conditions can cause HbA1c levels to fall, and not all of them are related to improved blood sugar control. One of the most clinically significant causes is haemolytic anaemia, a condition in which red blood cells are destroyed more rapidly than normal. Because HbA1c accumulates over the lifespan of a red blood cell, a shortened red cell survival time means less opportunity for glucose to bind to haemoglobin — resulting in a falsely low HbA1c reading.
Similarly, conditions associated with increased red blood cell turnover can lower HbA1c. These include:
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Iron deficiency anaemia — this typically raises HbA1c, because iron-deficient red cells survive longer and accumulate more glycated haemoglobin. Conversely, treating iron deficiency anaemia with iron supplementation can lower HbA1c as red cell turnover normalises. The direction of effect therefore depends on whether the anaemia is untreated or being corrected.
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Haemoglobinopathies such as sickle cell disease or thalassaemia, which alter haemoglobin structure and can interfere with standard HbA1c assays, making results unreliable
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Chronic kidney disease (CKD), which is associated with anaemia due to reduced erythropoietin production and may also affect red cell lifespan. In advanced CKD or in people receiving dialysis, HbA1c can become particularly unreliable, and alternative markers of glucose control may be more appropriate (see NICE NG203 and UK Kidney Association guidance)
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Recent significant blood loss or blood transfusion, which introduces new red blood cells that have had less time to accumulate glycated haemoglobin
Pregnancy is another important physiological state that can lower HbA1c. Increased red cell turnover during pregnancy means the test may underestimate average glucose levels. In line with NICE NG3 (Diabetes in pregnancy), HbA1c is not recommended for monitoring gestational diabetes mellitus (GDM). The standard approach for GDM monitoring is self-monitoring of capillary blood glucose. Continuous glucose monitoring (CGM) may be offered in specific circumstances — for example, it is routinely recommended for women with type 1 diabetes during pregnancy — but is not standard practice for GDM.
In all of these scenarios, the HbA1c result may not accurately reflect true glycaemic control. Clinicians should consider alternative tests or interpret results with caution when any of these conditions are present.
Key references: NICE NG28; NICE NG3 (Diabetes in pregnancy); NICE NG203 (Chronic kidney disease).
Medications and Treatments That Can Reduce HbA1c Levels
Diabetes medications including metformin, SGLT-2 inhibitors, GLP-1 receptor agonists, sulphonylureas, and insulin are designed to lower HbA1c; erythropoiesis-stimulating agents and certain other drugs can also reduce HbA1c indirectly.
A range of medications used in the management of type 2 diabetes are specifically designed to lower blood glucose and, consequently, HbA1c. When taken as prescribed and combined with appropriate lifestyle changes, these treatments can produce meaningful reductions in HbA1c over time. NICE NG28 outlines the recommended glucose-lowering therapies, which include:
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Metformin — the first-line treatment for most people with type 2 diabetes; it reduces hepatic glucose production and improves insulin sensitivity
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SGLT-2 inhibitors (e.g., empagliflozin, dapagliflozin) — promote urinary glucose excretion and have additional cardiovascular and renal benefits, making them a preferred option for people with established cardiovascular disease or CKD (subject to relevant NICE Technology Appraisals)
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GLP-1 receptor agonists (e.g., semaglutide, liraglutide) — stimulate insulin secretion in a glucose-dependent manner and suppress glucagon; also associated with weight loss and cardiovascular benefits in certain patient groups
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DPP-4 inhibitors (e.g., sitagliptin) — enhance incretin activity to improve post-meal glucose control
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Sulphonylureas (e.g., gliclazide) — stimulate insulin release from the pancreas
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Pioglitazone — a thiazolidinedione that improves insulin sensitivity; used in selected patients per NICE guidance
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Insulin therapy — used when oral agents are insufficient to achieve glycaemic targets
Beyond diabetes-specific medications, certain other drugs can influence HbA1c indirectly. Erythropoiesis-stimulating agents used in chronic kidney disease increase red blood cell production, which can dilute the proportion of glycated haemoglobin and lower the measured HbA1c. Dapsone and some antimalarial drugs can cause haemolysis, similarly affecting the result.
Patients should always inform their GP or diabetes care team of all medications they are taking, including over-the-counter products and supplements, as these may influence both blood glucose levels and the accuracy of HbA1c measurements. Do not start, stop, or alter any prescribed medication without first consulting your GP or diabetes team. If you experience a suspected side effect from any medicine, you can report it via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).
Key references: NICE NG28; relevant NICE Technology Appraisals for SGLT-2 inhibitors and GLP-1 receptor agonists; MHRA/EMC Summary of Product Characteristics (e.g., metformin, empagliflozin, semaglutide, gliclazide, insulin).
Lifestyle Factors That May Affect Your HbA1c Result
Dietary changes, regular physical activity, and weight loss are evidence-based lifestyle interventions that can meaningfully lower HbA1c in people with type 2 diabetes or non-diabetic hyperglycaemia.
Lifestyle modifications remain one of the most powerful and evidence-based ways to lower HbA1c in people with type 2 diabetes or non-diabetic hyperglycaemia (NDH). NICE guidance consistently emphasises structured lifestyle intervention as a cornerstone of diabetes management, often before or alongside pharmacological treatment.
Dietary changes have a direct impact on blood glucose levels. Reducing the intake of refined carbohydrates, sugary drinks, and ultra-processed foods can significantly lower post-meal glucose spikes. Diets such as the Mediterranean diet or low-carbohydrate approaches have demonstrated reductions in HbA1c in clinical trials. The NHS Diabetes Prevention Programme supports structured dietary education for those at risk.
Physical activity improves insulin sensitivity and promotes glucose uptake by muscle cells, both during and after exercise. UK Chief Medical Officers' guidelines recommend at least 150 minutes of moderate-intensity aerobic activity per week, alongside muscle-strengthening activities on at least two days per week, and reducing prolonged periods of sedentary behaviour. Even modest increases in activity can contribute to meaningful HbA1c reductions over time.
Weight loss is particularly impactful. Evidence from the DiRECT trial, conducted in the UK and published in The Lancet, demonstrated that significant weight loss through a structured low-calorie diet could achieve remission of type 2 diabetes in some individuals, with substantial falls in HbA1c.
Other lifestyle factors to consider include:
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Smoking cessation — smoking is associated with insulin resistance and poorer glycaemic control
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Alcohol reduction — excessive alcohol can cause unpredictable fluctuations in blood glucose
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Stress management and sleep quality — chronic stress and disrupted sleep are associated with elevated cortisol levels, which can raise blood glucose; managing these factors may therefore support better glycaemic control, though individual responses vary
These factors highlight that HbA1c is a dynamic marker, responsive to a wide range of behavioural and environmental influences.
Key references: NICE NG28; UK Chief Medical Officers' Physical Activity Guidelines; NHS Diabetes Prevention Programme; DiRECT trial (Lean et al., The Lancet, 2018).
When a Falling HbA1c May Require Further Investigation
An unexplained or unexpectedly low HbA1c should prompt clinical review, as it may indicate recurrent hypoglycaemia, an artificially low result due to a medical condition, or unintentional weight loss from an underlying illness.
Whilst a declining HbA1c is frequently a welcome finding, there are circumstances in which an unexplained or unexpectedly low result warrants careful clinical evaluation. A result that falls significantly without a clear explanation — such as a new medication, dietary change, or weight loss — should prompt further assessment.
One important concern is hypoglycaemia. In people treated with insulin or sulphonylureas, an overly low HbA1c may indicate recurrent episodes of low blood sugar, which can be dangerous. Hypoglycaemia is associated with cardiovascular risk, falls, cognitive impairment, and reduced quality of life. NICE NG28 advises that HbA1c targets should be individualised, and excessively tight control is not always appropriate — particularly in older adults or those with significant comorbidities.
An artificially low HbA1c due to the medical conditions described earlier — such as haemolytic anaemia, haemoglobinopathy, advanced CKD, or recent transfusion — may mask poor glycaemic control. In these cases, clinicians may request alternative markers of glucose control, such as:
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Fructosamine — reflects average glucose over the preceding two to three weeks; useful when red cell lifespan is abnormal
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Glycated albumin — another short-term marker of glucose control when HbA1c is unreliable
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Self-monitoring of blood glucose (SMBG) — capillary blood glucose testing remains a practical and widely used alternative
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Continuous glucose monitoring (CGM) — provides real-time glucose data and time-in-range metrics; in the NHS, CGM is routinely commissioned for people with type 1 diabetes and for specific type 2 diabetes indications (e.g., those on insulin with recurrent hypoglycaemia or impaired awareness of hypoglycaemia); availability for other type 2 diabetes patients may vary by local commissioning
A falling HbA1c in someone who has not made any deliberate changes to their diet, activity, or medication should also raise the possibility of unintentional weight loss, which may itself be a symptom of an underlying condition requiring investigation, including malignancy, thyroid disease, or gastrointestinal disorders.
Key references: NICE NG28 (HbA1c targets, hypoglycaemia management, monitoring); NICE NG17 (Type 1 diabetes in adults, CGM guidance).
When to Speak to Your GP About Your HbA1c Results
Contact your GP if your HbA1c changes significantly without explanation, if you experience symptoms of hypoglycaemia or anaemia, or if you have unexplained weight loss alongside a falling result.
If you have received an HbA1c result that has changed significantly — whether higher or lower than expected — it is always reasonable to discuss this with your GP or diabetes care team. Open communication about your results helps ensure that any necessary adjustments to your management plan are made promptly and safely.
You should contact your GP if you notice any of the following:
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Symptoms of hypoglycaemia, such as shakiness, sweating, confusion, or palpitations, particularly if these are occurring frequently or without warning. If you or someone else experiences a severe hypoglycaemic episode — including loss of consciousness or a seizure — call 999 immediately
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Unexplained weight loss alongside a falling HbA1c, which may indicate an underlying health condition requiring investigation
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Symptoms of anaemia, such as persistent fatigue, breathlessness, or pallor, which could be affecting the accuracy of your HbA1c result
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Uncertainty about your current medications and whether they are contributing to changes in your result
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Concerns about your diabetes management targets, especially if you are elderly, have cardiovascular disease, or have experienced recurrent low blood sugar episodes
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If you are pregnant or planning a pregnancy, contact your midwife or diabetes in pregnancy team promptly, as monitoring and targets differ during pregnancy in line with NICE NG3
It is also worth noting that HbA1c is just one tool in diabetes monitoring. Your GP or diabetes nurse may also assess blood pressure, cholesterol, kidney function, and foot health as part of your annual diabetes review — the NHS recommends nine key care processes as part of this review.
If you are not currently under regular review for diabetes or non-diabetic hyperglycaemia, ask your GP about being referred to a structured education programme such as the NHS Diabetes Prevention Programme or DESMOND (Diabetes Education and Self-Management for Ongoing and Newly Diagnosed). Proactive engagement with your healthcare team remains the most effective way to understand and act upon your HbA1c results safely.
Key references: NICE NG28; NICE NG3 (Diabetes in pregnancy); NHS nine care processes for annual diabetes review.
Frequently Asked Questions
Apakah hasil HbA1c yang rendah selalu berarti kontrol gula darah membaik?
Tidak selalu. Meskipun HbA1c yang rendah sering mencerminkan perbaikan kontrol gula darah, hasil yang rendah juga dapat disebabkan oleh kondisi medis seperti anemia hemolitik, penyakit ginjal kronis, atau kehamilan yang memengaruhi akurasi pengukuran. Penting untuk mendiskusikan hasil ini dengan dokter untuk memastikan interpretasi yang tepat.
Kondisi medis apa saja yang dapat menyebabkan hasil HbA1c turun secara artifisial?
Kondisi yang memperpendek masa hidup sel darah merah — termasuk anemia hemolitik, hemoglobinopati (seperti sickle cell disease atau thalassaemia), penyakit ginjal kronis stadium lanjut, dan transfusi darah baru-baru ini — dapat menyebabkan HbA1c tampak lebih rendah dari kadar glukosa darah yang sebenarnya.
Kapan saya harus menemui dokter terkait perubahan hasil HbA1c saya?
Segera hubungi dokter jika HbA1c Anda turun secara signifikan tanpa perubahan obat, diet, atau berat badan yang jelas; jika Anda mengalami gejala hipoglikemia seperti gemetar atau kebingungan; atau jika terdapat penurunan berat badan yang tidak disengaja. Jika terjadi hipoglikemia berat dengan kehilangan kesadaran, hubungi layanan darurat segera.
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