Chronic liver disease decreased HbA1c is a clinically important phenomenon that can mislead both patients and clinicians into believing blood sugar control is better than it actually is. HbA1c — the standard long-term blood glucose test — relies on red blood cells surviving their normal 120-day lifespan. In chronic liver disease, haemolysis, anaemia, and altered red cell turnover can shorten this lifespan, producing falsely low HbA1c readings even when blood glucose is dangerously elevated. Understanding why this occurs, which alternative tests are available, and when to seek specialist review is essential for safe diabetes management in anyone living with significant liver disease.

Why Chronic Liver Disease Can Lower HbA1c Readings

Chronic liver disease lowers HbA1c by disrupting red blood cell lifespan through haemolysis and anaemia, causing the test to underestimate true blood glucose even when hyperglycaemia is present.

Have any more questions about this? Message our pharmaceutical team to get more info →

HbA1c — glycated haemoglobin — is a widely used blood test that reflects average blood glucose levels over the preceding two to three months. It works by measuring the proportion of haemoglobin molecules that have glucose attached to them. In healthy individuals, this provides a reliable snapshot of long-term glycaemic control. However, in people with chronic liver disease (CLD), this measurement can be misleadingly reduced in certain circumstances, even when blood glucose levels are actually elevated.

The liver plays a central role in glucose metabolism, including glycogen storage, gluconeogenesis, and insulin clearance. When liver function is impaired — as seen in conditions such as cirrhosis, non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease, or viral hepatitis — these processes are disrupted. Paradoxically, despite the metabolic dysfunction that often leads to insulin resistance and elevated blood glucose, the HbA1c reading may appear falsely low. This phenomenon is sometimes referred to as a 'spuriously low HbA1c' and has important clinical implications for diagnosing and managing diabetes in this patient group. The extent to which HbA1c is affected depends on the degree of anaemia, haemolysis, and hypersplenism present, as well as the overall severity of liver disease.

Understanding why this occurs requires looking beyond glucose metabolism itself and towards the behaviour of red blood cells in the context of liver disease. Several interconnected mechanisms — principally haemolysis, anaemia, and altered red cell turnover — can reduce the reliability of HbA1c as a glycaemic marker. Clinicians and patients alike should be aware that a 'normal' or 'low' HbA1c result does not necessarily indicate good blood sugar control in the presence of significant liver pathology. NICE guideline NG28 (Type 2 diabetes in adults) and NG17 (Type 1 diabetes in adults) both acknowledge that HbA1c may be unreliable in conditions affecting red cell turnover.

How Liver Disease Affects Red Blood Cells and HbA1c

Liver disease shortens red cell survival via haemolysis, hypersplenism, anaemia, and impaired erythropoiesis, each reducing the time available for glucose to attach to haemoglobin and artificially lowering HbA1c.

The accuracy of HbA1c depends on red blood cells (RBCs) having a normal lifespan of approximately 120 days. Glucose attaches to haemoglobin gradually over this period, so a longer-lived red cell accumulates more glycated haemoglobin. Because HbA1c is expressed as a proportion of total haemoglobin, it is the shortened RBC lifespan — rather than changes in blood volume — that directly reduces HbA1c values regardless of actual blood glucose levels.

Key mechanisms include:

• Haemolysis: Liver disease — particularly cirrhosis — is associated with increased red cell destruction. Conditions such as hypersplenism (an enlarged, overactive spleen) cause accelerated RBC breakdown. Shorter-lived red cells have less time to accumulate glycated haemoglobin, artificially lowering HbA1c.

• Anaemia: Chronic liver disease frequently causes anaemia through multiple routes, including gastrointestinal bleeding (e.g., from oesophageal varices), nutritional deficiencies (iron, folate, B12), and bone marrow suppression. Anaemia alters the RBC pool and can distort HbA1c readings.

• Altered erythropoiesis: Liver disease can impair the production of erythropoietin and other factors that regulate red cell production, further disrupting normal RBC turnover and shortening effective red cell survival.

• Blood transfusions: Some patients with liver disease receive blood transfusions, which introduce donor red cells of varying ages and glycation status. Following a transfusion, HbA1c interpretation is unreliable for approximately three months — the lifespan of the transfused cells.

Collectively, these haematological disturbances mean that HbA1c may substantially underestimate true glycaemic burden in patients with CLD, potentially masking poorly controlled diabetes and delaying appropriate treatment. The British Society of Gastroenterology (BSG) and British Association for the Study of the Liver (BASL) guidance on cirrhosis management provides further context on hypersplenism and anaemia as complications of advanced liver disease.

Limitations of HbA1c for Monitoring Diabetes in Liver Disease

HbA1c can significantly underestimate mean blood glucose in cirrhosis or advanced fibrosis, with the greatest inaccuracy seen in decompensated disease; fasting plasma glucose or OGTT should be used for diagnosis when HbA1c is unreliable.

Given the mechanisms described above, HbA1c has well-recognised limitations as a glycaemic monitoring tool in chronic liver disease. Studies have demonstrated that HbA1c can underestimate mean blood glucose by a clinically significant margin in patients with cirrhosis or advanced liver fibrosis. This means that a patient may appear to have acceptable glycaemic control on paper whilst actually experiencing sustained hyperglycaemia — a situation that increases the risk of diabetes-related complications including nephropathy, neuropathy, and cardiovascular disease.

The degree of HbA1c underestimation tends to correlate with the severity of liver disease. Patients with decompensated cirrhosis — characterised by jaundice, ascites, or hepatic encephalopathy — are at greatest risk of having a falsely reassuring HbA1c. Even in compensated cirrhosis or significant fibrosis, the test may not be fully reliable. It is also worth noting that HbA1c can be affected by haemoglobin variants (e.g., sickle cell trait, thalassaemia), which are separate considerations but may co-exist in some patients.

From a diagnostic standpoint, using HbA1c alone to screen for or diagnose diabetes in patients with known liver disease is problematic. NICE guideline NG28 (Type 2 diabetes in adults) and NG17 (Type 1 diabetes in adults) both acknowledge that HbA1c may not be appropriate in certain clinical circumstances, including conditions affecting red cell turnover. When HbA1c is deemed unreliable, diagnosis should be based on fasting plasma glucose or an oral glucose tolerance test (OGTT), in line with NICE and WHO guidance. Clinicians should interpret HbA1c results in the context of the full clinical picture — including liver function tests, full blood count, and symptoms of hyperglycaemia — rather than relying on HbA1c in isolation.

Alternative Tests for Assessing Blood Sugar Control

Fructosamine, glycated albumin, self-monitoring of blood glucose, and continuous glucose monitoring (CGM) are the main alternatives when HbA1c is unreliable, though fructosamine is itself affected by low albumin levels common in advanced liver disease.

When HbA1c is deemed unreliable due to chronic liver disease, alternative methods of assessing glycaemic control should be considered. It is important to distinguish between tools used for diagnosing diabetes and those used for ongoing monitoring.

For diagnosis: When HbA1c cannot be relied upon, fasting plasma glucose or an oral glucose tolerance test (OGTT) should be used to diagnose or exclude diabetes, in accordance with NICE and WHO guidance.

For ongoing monitoring:

Fructosamine is one of the most commonly used alternatives. It measures glycated serum proteins — primarily albumin — and reflects average blood glucose over the preceding two to three weeks. Because it is not dependent on red cell lifespan, it avoids the haematological confounders that affect HbA1c. However, fructosamine has its own limitations: it is influenced by serum albumin levels, which are frequently low in advanced liver disease due to impaired hepatic synthesis. A low albumin will itself lower fructosamine, potentially masking poor glycaemic control. Albumin-adjusted interpretation should be considered where possible.

Glycated albumin is a more specific measure of albumin glycation and may offer advantages over total fructosamine in patients with hypoalbuminaemia, though it is not yet widely available in routine NHS practice.

Self-monitoring of blood glucose (SMBG) using a glucometer remains a practical and accessible option. Regular capillary blood glucose measurements — particularly fasting and postprandial readings — can provide valuable real-time data. For patients with diabetes and liver disease, structured SMBG may be the most pragmatic approach to day-to-day management.

Continuous glucose monitoring (CGM) devices, such as the FreeStyle Libre, are increasingly available on the NHS for eligible patients with diabetes. CGM provides detailed glucose profiles and time-in-range data, which can be particularly informative when HbA1c is unreliable. Eligibility criteria for NHS-funded CGM are set out in NICE guideline NG17 (for adults with type 1 diabetes) and NICE guideline NG28 (for adults with type 2 diabetes). Patients should discuss eligibility with their diabetes care team.

If you experience any suspected side effects from medicines used to manage your diabetes or liver disease, these can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

NICE and NHS Guidance on Diabetes Monitoring in Liver Disease

NICE guidelines NG28, NG17, and NG49 collectively advise that HbA1c may be unreliable in conditions affecting red cell turnover, recommending clinical judgement and alternative markers; metformin and other antidiabetics require hepatic impairment review via the BNF and SmPC.

NICE does not currently publish a single, dedicated guideline specifically addressing diabetes monitoring in chronic liver disease; however, relevant recommendations are distributed across several key documents. NICE guideline NG28 (Type 2 diabetes in adults) and NG17 (Type 1 diabetes in adults) both acknowledge that HbA1c may be unreliable in certain conditions affecting red cell turnover, advising clinicians to use clinical judgement and alternative measures where appropriate. NICE guideline NG49 (Non-alcoholic fatty liver disease) highlights the frequent co-existence of NAFLD and type 2 diabetes, underscoring the importance of robust glycaemic monitoring in this population.

The NHS Long Term Plan and associated diabetes programmes emphasise structured diabetes reviews, which should include an assessment of whether standard monitoring tools remain appropriate for individual patients. For those with significant liver disease, this review should prompt consideration of alternative glycaemic markers and more frequent clinical assessment.

The BSG and BASL have published guidance on the management of cirrhosis and its complications, which includes recognition that diabetes commonly coexists with, and may arise as a direct consequence of, chronic liver disease — sometimes described in the literature as hepatogenous diabetes. This may require tailored management strategies, as some antidiabetic medicines carry cautions or are contraindicated in advanced liver disease. For example, metformin carries a caution in hepatic impairment due to the risk of lactic acidosis; prescribers should consult the current metformin Summary of Product Characteristics (SmPC), available via the MHRA's electronic Medicines Compendium (eMC), and the BNF monograph for up-to-date guidance on hepatic impairment cautions and contraindications. Similar considerations apply to other antidiabetic drug classes, and the relevant SmPC and BNF entries should be reviewed when selecting or reviewing therapy in this context.

When to Seek Specialist Review for Abnormal HbA1c Results

Specialist review is warranted when HbA1c is discordant with capillary glucose readings, when cirrhosis or advanced fibrosis is diagnosed, or when unexplained hypoglycaemia or new anaemia develops in a patient with diabetes and liver disease.

Patients and clinicians should be alert to situations where HbA1c results appear inconsistent with clinical symptoms or other test findings. If a person with known or suspected chronic liver disease has an HbA1c that seems unexpectedly low — particularly in the context of symptoms such as excessive thirst, frequent urination, unexplained weight loss, or fatigue — this warrants prompt further evaluation rather than reassurance.

Seek emergency care (call 999 or go to A&E) if any of the following occur:

• Symptoms of severe hyperglycaemia with ketones, dehydration, or altered consciousness (possible diabetic ketoacidosis or hyperosmolar hyperglycaemic state)

• Signs of decompensated liver disease, such as sudden jaundice with confusion, significant gastrointestinal bleeding, or rapidly worsening ascites

Seek same-day GP or urgent clinic review if:

• Capillary blood glucose readings are persistently above 20 mmol/L

• There are recurrent unexplained hypoglycaemic episodes

The following situations should prompt referral to or discussion with a specialist (hepatologist, diabetologist, or both):

• Discordance between HbA1c and capillary blood glucose readings: If home glucose monitoring consistently shows elevated readings but HbA1c appears normal or low, the HbA1c is likely unreliable.

• New or worsening anaemia in a person with diabetes and liver disease: This may signal haemolysis or bleeding, both of which will affect HbA1c validity.

• Diagnosis of cirrhosis or advanced fibrosis: At this stage, routine HbA1c monitoring should be formally reviewed and alternative strategies discussed.

• Unexplained hypoglycaemic episodes: Advanced liver disease impairs gluconeogenesis, increasing hypoglycaemia risk — particularly in patients on insulin or sulphonylureas.

• Initiation or review of antidiabetic medication: Some agents require dose adjustment or avoidance in hepatic impairment; refer to the relevant SmPC and BNF.

Patients are encouraged to raise concerns about their monitoring plan with their GP or diabetes nurse, who can facilitate onward referral if needed. A coordinated approach between hepatology and diabetes services is ideal for managing this complex patient group safely and effectively. Early specialist involvement can prevent both under-treatment of hyperglycaemia and dangerous hypoglycaemia, improving long-term outcomes.

Key UK references and resources:

• NICE NG28: Type 2 diabetes in adults (nice.org.uk/guidance/ng28)

• NICE NG17: Type 1 diabetes in adults (nice.org.uk/guidance/ng17)

• NICE NG49: Non-alcoholic fatty liver disease (nice.org.uk/guidance/ng49)

• BNF: Antidiabetic drugs and hepatic impairment (bnf.nice.org.uk)

• MHRA eMC: Metformin SmPC (medicines.org.uk/emc)

• MHRA Yellow Card scheme: yellowcard.mhra.gov.uk

• NHS: HbA1c test (nhs.uk)

• BSG/BASL: Guidance on the management of cirrhosis

Frequently Asked Questions