Does krill oil reduce HbA1c? It is a question increasingly asked by people managing type 2 diabetes or non-diabetic hyperglycaemia who are exploring dietary supplements alongside conventional treatment. Krill oil, derived from Antarctic krill, provides omega-3 fatty acids EPA and DHA in a phospholipid-bound form, and also contains the antioxidant astaxanthin. While there are plausible biological mechanisms by which omega-3s might support metabolic health, the clinical evidence specifically linking krill oil to meaningful reductions in HbA1c remains limited and inconclusive. This article examines what the current research shows and what UK patients should know.

What Is Krill Oil and How Might It Affect Blood Glucose?

Krill oil provides omega-3 fatty acids with proposed anti-inflammatory effects that may theoretically improve insulin sensitivity, but these mechanisms have not translated into consistent HbA1c reductions in clinical trials.

Krill oil is a dietary supplement derived from Antarctic krill (Euphausia superba), small crustaceans rich in omega-3 fatty acids — primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Unlike fish oil, the omega-3s in krill oil are largely bound to phospholipids rather than triglycerides. Some researchers have suggested this may improve their absorption and bioavailability compared with fish oil, but the evidence from head-to-head studies is inconsistent and this remains an area of ongoing investigation rather than established fact.

The theoretical basis for krill oil influencing blood glucose regulation centres on several mechanisms. Omega-3 fatty acids have anti-inflammatory properties, and chronic low-grade inflammation is closely associated with insulin resistance — a key driver of type 2 diabetes. It has been proposed that by reducing inflammatory markers such as C-reactive protein (CRP), omega-3s might help improve insulin sensitivity at the cellular level. However, these mechanistic hypotheses are based largely on preclinical and observational data; they have not translated into consistent reductions in HbA1c in randomised controlled trials (RCTs).

Krill oil also contains astaxanthin, a naturally occurring antioxidant carotenoid. Astaxanthin has been studied in preclinical models for its potential to reduce oxidative stress, which is implicated in pancreatic beta-cell dysfunction. Readers should be aware that laboratory findings of this kind do not reliably translate into clinically meaningful outcomes in humans. The UK Scientific Advisory Committee on Nutrition (SACN) has not identified omega-3 supplementation as beneficial for blood glucose control, and there is no official guidance from NICE or the MHRA endorsing krill oil as a treatment for blood glucose management. It should not be considered a substitute for prescribed diabetes therapies.

Understanding HbA1c and Its Role in Diabetes Management

HbA1c reflects average blood glucose over two to three months; in the UK, 48 mmol/mol or above on two samples confirms type 2 diabetes, and it is the primary monitoring tool recommended by NICE NG28.

HbA1c — glycated haemoglobin — is a blood test that reflects average blood glucose levels over the preceding two to three months. When glucose circulates in the bloodstream, it binds irreversibly to haemoglobin within red blood cells. The higher the blood glucose over time, the greater the proportion of glycated haemoglobin. Results are expressed in millimoles per mole (mmol/mol) in the UK, in line with IFCC standardisation.

According to NICE guideline NG28 (Type 2 Diabetes in Adults: Management) and supporting NHS and UKHSA guidance, HbA1c is the primary diagnostic and monitoring tool for type 2 diabetes and non-diabetic hyperglycaemia (NDH):

• Below 42 mmol/mol: Normal range

• 42–47 mmol/mol: Non-diabetic hyperglycaemia (NDH) — sometimes referred to as prediabetes, though NDH is the preferred UK term

• 48 mmol/mol or above: Diagnostic threshold for type 2 diabetes (in line with WHO 2011 guidance, when confirmed on a second sample in asymptomatic individuals)

For people already diagnosed with type 2 diabetes, NICE NG28 recommends an individualised HbA1c target, commonly 48–53 mmol/mol, depending on treatment regimen and patient factors. Sustained reductions in HbA1c are strongly associated with reduced risk of microvascular complications, including diabetic retinopathy, nephropathy, and neuropathy.

It is important to note that HbA1c may not be a reliable measure in certain situations, including pregnancy, haemoglobinopathies (such as sickle cell disease or thalassaemia), conditions affecting red blood cell turnover (such as haemolytic anaemia), recent blood transfusion, chronic kidney disease, HIV, and in children or those with suspected type 1 diabetes. In these circumstances, alternative measures of glycaemic control should be used and results interpreted with clinical caution.

Because HbA1c captures long-term glycaemic trends rather than a single moment in time, it is a robust and clinically meaningful endpoint in diabetes research. Any supplement or intervention claiming to reduce HbA1c must therefore demonstrate consistent, sustained effects on blood glucose across weeks and months — a high evidential bar that many dietary supplements have not met in well-designed clinical trials.

What the Clinical Evidence Says About Krill Oil and HbA1c

Current clinical evidence, including Cochrane reviews of omega-3 supplementation, does not demonstrate a significant reduction in HbA1c from krill oil or fish oil in people with type 2 diabetes.

The direct clinical evidence examining krill oil's effect on HbA1c specifically is limited and, at present, inconclusive. Most of the available research on omega-3 fatty acids and glycaemic control has been conducted using fish oil rather than krill oil, making it difficult to draw firm conclusions specific to krill oil supplementation.

A number of meta-analyses and systematic reviews of omega-3 supplementation in people with type 2 diabetes have produced mixed results. A Cochrane review on omega-3 polyunsaturated fatty acids (PUFAs) for type 2 diabetes found that omega-3 supplementation did not significantly reduce HbA1c, despite beneficial effects on triglyceride levels. Other systematic reviews and meta-analyses have similarly reported no statistically significant effect on HbA1c, even where modest improvements in fasting glucose or insulin sensitivity were observed in some analyses. The SACN review of omega-3 fatty acids and health did not identify evidence supporting a role for omega-3 supplements in blood glucose control.

Studies specifically using krill oil are fewer in number and generally smaller in scale. Some short-term trials have reported improvements in lipid profiles — particularly reductions in triglycerides — but effects on LDL cholesterol have been inconsistent across studies. Robust, peer-reviewed evidence demonstrating a clinically meaningful reduction in HbA1c from krill oil supplementation is currently lacking. Many available studies also have methodological limitations, including small sample sizes, short durations, and inadequate dietary control.

NICE does not recommend omega-3 supplements for cardiovascular disease (CVD) prevention in most people (NICE NG238); the licensed omega-3 preparation icosapent ethyl has specific, restricted indications that do not apply to over-the-counter krill oil products.

In summary, while a biological rationale exists for omega-3s to support metabolic health, there is no strong clinical evidence at present that krill oil reliably reduces HbA1c in humans. Patients should be cautious about interpreting preliminary or industry-funded research as definitive proof of benefit.

Safety, Dosage, and Considerations for UK Patients

Krill oil is generally safe for most adults but may interact with anticoagulants, is unsuitable for those with shellfish allergy, and carries no evidence-based therapeutic dose for glycaemic effects.

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Krill oil is generally considered safe for most adults when taken as directed. There is no established therapeutic dose for glycaemic effects, and the wide range of doses seen in commercial products (commonly 500 mg to 3,000 mg per day) reflects manufacturer recommendations rather than evidence-based clinical guidance. Patients should follow the instructions on the product label and seek advice from their GP or pharmacist before starting supplementation. Krill oil is widely available over the counter in UK pharmacies and health food shops.

As with all supplements, there are important safety considerations:

Potential adverse effects and interactions include:

• Anticoagulant and antiplatelet interaction: Krill oil may have mild antiplatelet properties. The evidence for a clinically significant increase in bleeding risk is limited, but as a precaution, patients taking anticoagulants such as warfarin or direct oral anticoagulants (DOACs) such as apixaban or rivaroxaban, or antiplatelet medicines, should discuss use with their GP or pharmacist before starting. Those on warfarin should have their INR monitored if they start or stop krill oil.

• Perioperative use: If you are scheduled for surgery, inform your surgical team that you are taking krill oil. They will advise whether and when to stop it; guidance varies depending on the procedure and individual circumstances.

• Shellfish allergy: Because krill is a crustacean, individuals with shellfish allergies should avoid krill oil or seek medical advice before taking it.

• Gastrointestinal effects: Some users report mild nausea, loose stools, or a fishy aftertaste, particularly at higher doses.

• Pregnancy and breastfeeding: The safety of krill oil during pregnancy and breastfeeding has not been fully established. Pregnant women should also check whether any krill oil product contains vitamin A, as excessive vitamin A intake is harmful in pregnancy. Seek advice from a GP or midwife before use.

If you experience a suspected adverse reaction to krill oil or any other supplement, you can report it to the MHRA via the Yellow Card Scheme at yellowcard.mhra.gov.uk.

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In the UK, food supplements including krill oil are regulated by the Food Standards Agency (FSA) rather than the MHRA, meaning they are not subject to the same rigorous pre-market efficacy and safety testing as licensed medicines. Under GB Nutrition and Health Claims rules, supplement products cannot legally claim to treat, cure, or prevent any disease, including diabetes. A product being legally sold does not imply it has proven clinical efficacy.

For people with diabetes who are considering krill oil, supplementation should be viewed as a potential adjunct to — never a replacement for — evidence-based treatments such as metformin, GLP-1 receptor agonists, SGLT-2 inhibitors, or lifestyle interventions recommended by NICE NG28.

When to Speak to Your GP or Diabetes Care Team

Anyone with diabetes or NDH should consult their GP before starting krill oil, especially if taking prescribed medications, and should never replace evidence-based diabetes treatments with supplements.

If you are considering taking krill oil and have diabetes or non-diabetic hyperglycaemia (NDH), it is always advisable to discuss this with your GP or diabetes care team before starting supplementation. This is particularly important if you are taking prescribed medications, as interactions — even with seemingly benign supplements — can have clinical consequences.

Seek urgent or same-day medical attention if you experience:

• Symptoms that may suggest diabetic ketoacidosis (DKA): abdominal pain, vomiting, rapid or laboured breathing, drowsiness, or confusion, particularly if blood glucose is very high

• Severe or recurrent hypoglycaemia (very low blood glucose)

• Very high blood glucose readings that do not respond to your usual management

Contact your GP or diabetes nurse if:

• Your HbA1c has risen above your agreed target at your last review

• You are considering stopping or reducing prescribed diabetes medication in favour of supplements

• You experience unexplained changes in blood glucose readings after starting any new supplement

• You are pregnant, planning pregnancy, or breastfeeding

• You have a history of bleeding disorders, are taking anticoagulant or antiplatelet therapy, or are scheduled for surgery

It is also worth raising the topic of omega-3 supplementation during your annual diabetes review, which is recommended by NICE NG28 for all people with type 2 diabetes. Your care team can help contextualise the evidence, review your current lipid profile, and advise whether any supplement might be appropriate alongside your existing management plan. Note that NICE does not recommend omega-3 supplements for CVD prevention in most people; over-the-counter krill oil is not equivalent to licensed omega-3 preparations used in specific clinical settings.

Ultimately, the most evidence-based approaches to lowering HbA1c remain: a balanced diet low in refined carbohydrates, regular physical activity, weight management where appropriate, smoking cessation, and adherence to prescribed medications. Krill oil may offer some lipid benefits — particularly triglyceride reduction — for certain individuals, but it should not be relied upon as a primary strategy for glycaemic control. Always seek personalised advice from a qualified healthcare professional rather than relying on supplement marketing claims.

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