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Omega-3 (DHA) for Type 2 Diabetes: What the Randomized Trials Show

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In randomized trials of people with or at risk of type 2 diabetes, omega-3 (EPA/DHA) supplementation produced mixed...

In randomized trials of people with or at risk of type 2 diabetes, omega-3 (EPA/DHA) supplementation produced mixed glycemic results: some trials reported lower fasting insulin, HOMA-IR, or HbA1c [1][11], while others found no change in fasting glucose, insulin, HbA1c, or inflammatory markers [2][9][4].

Key Findings

  • A 12-week fish oil trial in 201 middle-aged and older adults found that supplementation dose-dependently increased serum EPA and DHA while decreasing fasting insulin and the HOMA-IR index (p<0.01 after controlling for confounders), with fasting blood glucose trending downward versus baseline within each fish oil group (p<0.01 vs. baseline) [1].
  • In 185 Chinese type 2 diabetes patients given 2 g/day EPA+DHA for 180 days, HbA1c decreased in the fish oil group versus the corn oil group (p=0.037), but no group-by-time interaction was seen for HOMA-IR, fasting insulin, or glucose [11].
  • A trial in 100 type 2 diabetes patients found that 12 weeks of EPA plus nano-curcumin lowered blood insulin (MD -1.44 [-2.70, -0.17]) but produced no significant between-group differences in fasting blood sugar, HOMA-IR, QUICKI, or HbA1c (all p>0.05) [2].
  • In the largest trial reviewed, 1312 adults with type 2 diabetes taking 1 g/day EPA+DHA showed no significant difference versus placebo in IL-6, hsCRP, or NT-proBNP over 5 years [4].
  • A high-dose trial (2 g/day, given as 1 g/day EPA + 1 g/day DHA) in 74 patients with type 2 diabetes and atherosclerosis found no change in HbA1c, insulin, lipids, platelet function, or systemic inflammation after 3 months [9].
  • Over 1 year, EPA+DHA (1.86 g EPA + 1.5 g DHA daily) was associated with no change in urine albumin-to-creatinine ratio in diabetic subjects, whereas those not receiving it had a 72.3% increase (p<0.001) [8].

Study Details

Effects of fish oil intervention on type 2 diabetes early risk novel biomarkers in healthy middle-aged and elderly adults: a double-blind randomized controlled trial
Nian Z, Lin Y, Tang W et al. — Food Funct (2025)
Over 12 weeks, fish oil dose-dependently raised serum EPA and DHA while lowering fasting insulin and HOMA-IR (p<0.01 after controlling for confounders), with fasting blood glucose trending downward versus baseline within each fish oil group (p<0.01 vs. baseline).
201 participantsModerate
Effects of n-3 fatty acid supplements on glycemic traits in Chinese type 2 diabetic patients: A double-blind randomized controlled trial
Zheng JS, Lin M, Fang L et al. — Mol Nutr Food Res (2016)
Fish oil (2 g/day EPA+DHA) for 180 days lowered HbA1c versus corn oil (p=0.037), but showed no group-by-time interaction for HOMA-IR, fasting insulin, or glucose.
185 participantsModerate
Effects of long-term vitamin D and n-3 fatty acid supplementation on inflammatory and cardiac biomarkers in patients with type 2 diabetes: secondary analyses from a randomised controlled trial
Limonte CP, Zelnick LR, Ruzinski J et al. — Diabetologia (2021)
n-3 fatty acids (1 g/day EPA+DHA) showed no significant difference versus placebo in IL-6, hsCRP, or NT-proBNP over 5 years.
1,312 participantsHigh
The effect of curcumin and high-content eicosapentaenoic acid supplementations in type 2 diabetes mellitus patients: a double-blinded randomized clinical trial
Asghari KM, Saleh P, Salekzamani Y et al. — Nutr Diabetes (2024)
Twelve weeks of EPA plus nano-curcumin lowered blood insulin (MD -1.44) but produced no significant between-group changes in fasting blood sugar, HOMA-IR, QUICKI, or HbA1c (all p>0.05).
100 participantsModerate
Treatment with high-dose n-3 PUFAs has no effect on platelet function, coagulation, metabolic status or inflammation in patients with atherosclerosis and type 2 diabetes
Poreba M, Mostowik M, Siniarski A et al. — Cardiovasc Diabetol (2017)
High-dose n-3 PUFAs (2 g/day, given as 1 g/day EPA + 1 g/day DHA) for 3 months produced no change in HbA1c, insulin, lipids, platelet function, or systemic inflammation.
74 participantsModerate
Eicosapentaenoic and Docosahexaenoic Acids Attenuate Progression of Albuminuria in Patients With Type 2 Diabetes Mellitus and Coronary Artery Disease
Elajami TK, Alfaddagh A, Lakshminarayan D et al. — J Am Heart Assoc (2017)
Over 1 year, urine albumin-to-creatinine ratio did not change in diabetic subjects receiving EPA+DHA, whereas it rose 72.3% (p<0.001) in those not receiving it.
262 participantsModerate
Effects of DHA-enriched fish oil on monocyte/macrophage activation marker sCD163, asymmetric dimethyl arginine, and insulin resistance in type 2 diabetic patients
Toupchian O, Sotoudeh G, Mansoori A et al. — J Clin Lipidol (2016)
Eight weeks of 2.4 g/day DHA-enriched fish oil significantly decreased serum sCD163, triglycerides, waist circumference, and weight-to-height ratio versus control.
72 participantsModerate
Effects of DHA-enriched fish oil on gene expression levels of p53 and NF-κB and PPAR-γ activity in PBMCs of patients with T2DM: A randomized, double-blind, clinical trial
Naeini Z, Toupchian O, Vatannejad A et al. — Nutr Metab Cardiovasc Dis (2020)
Eight weeks of 2400 mg/day DHA-rich fish oil increased PPAR-γ activity in PBMCs (p<0.01; between-group p=0.03), with no significant change in p53 or NF-κB expression.
50 participantsModerate

Practical Takeaway

The randomized evidence on omega-3 (EPA/DHA) for type 2 diabetes is mixed and depends heavily on the specific outcome, dose, and trial duration, so it should not be viewed as a substitute for prescribed diabetes care. Some trials report modest improvements in fasting insulin, HOMA-IR, or HbA1c [1][11], while several well-controlled trials found no benefit for glycemic control or systemic inflammation [2][4][9]; that same high-dose trial, reported separately for endothelial function, also showed no improvement in flow-mediated dilation [7]. Anyone with type 2 diabetes considering omega-3 should discuss it with their clinician, since responses varied widely across studies.

Summary

This summary reviews randomized controlled trials testing omega-3 fatty acids (EPA and DHA, often as fish oil) on glycemic and cardiometabolic markers in people with or at risk of type 2 diabetes. Results are mixed and endpoint-specific: some trials report lower fasting insulin, HOMA-IR, or HbA1c, while others show no change in glycemic control, inflammation, or endothelial function. Effects appear to vary by dose, duration, and which outcome is measured.

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Frequently Asked Questions

Does omega-3 lower blood sugar or HbA1c in type 2 diabetes?

The randomized evidence is mixed. One trial of 2 g/day EPA+DHA for 180 days reported lower HbA1c versus corn oil (p=0.037), though it found no group-by-time interaction for HOMA-IR, fasting insulin, or glucose [11]. A separate 12-week fish oil trial reported lower fasting insulin and HOMA-IR with fasting glucose trending downward versus baseline within each fish oil group [1], while other trials found no significant between-group change in fasting blood sugar or HbA1c [2][9].

Evidence:RCT (2025)[#1]. See full reference list below.

Does omega-3 reduce inflammation in people with type 2 diabetes?

Not consistently. In a 5-year trial of 1312 adults with type 2 diabetes, 1 g/day EPA+DHA showed no significant difference versus placebo in IL-6, hsCRP, or NT-proBNP [4]. A 3-month high-dose (2 g/day) trial also found no change in systemic inflammation markers [9], although one DHA-enriched fish oil trial reported lower sCD163 [10].

Evidence:RCT (2021)[#4]. See full reference list below.

How much EPA and DHA were used in these trials?

Doses varied widely across the randomized trials, ranging from about 0.31 to 1.24 g/day EPA+DHA in a dose-finding fish oil study [1], to 1 g/day [4], 2 g/day [11], and a high-dose 2 g/day regimen given as 1 g EPA + 1 g DHA [9]. Because doses, formulations, and durations differed, results are not directly comparable between trials.

Evidence:RCT (2025)[#1]. See full reference list below.

Did omega-3 affect kidney or cardiovascular markers in type 2 diabetes?

In one 1-year trial, urine albumin-to-creatinine ratio did not change in diabetic subjects taking EPA+DHA, while it rose 72.3% (p<0.001) in those not taking it [8]. The 3-month high-dose (2 g/day) trial in patients with type 2 diabetes and very high cardiovascular risk, reported separately for endothelial function, found no improvement in flow-mediated dilation [7]; that same trial showed no change in platelet, coagulation, metabolic, or inflammation markers [9].

Evidence:RCT (2018)[#7]. See full reference list below.

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Bottom line: Omega-3s have strong evidence for heart, brain, and joint health. Take 1,000-2,000mg EPA+DHA daily — choose triglyceride form fish oil or algal oil for vegans.

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References

  1. RCTNian Z, Lin Y, Tang W et al. (2025). Effects of fish oil intervention on type 2 diabetes early risk novel biomarkers in healthy middle-aged and elderly adults: a double-blind randomized controlled trial. Food Funct. DOI PubMed
  2. RCTAsghari KM, Saleh P, Salekzamani Y et al. (2024). The effect of curcumin and high-content eicosapentaenoic acid supplementations in type 2 diabetes mellitus patients: a double-blinded randomized clinical trial. Nutr Diabetes. DOI PubMed
  3. RCTKuang X, Shao X, Li H et al. (2023). Lipid extract from blue mussel (Mytilus edulis) improves glycemic traits in Chinese type 2 diabetic mellitus patients: a double-blind randomized controlled trial. J Sci Food Agric. DOI PubMed
  4. RCTLimonte CP, Zelnick LR, Ruzinski J et al. (2021). Effects of long-term vitamin D and n-3 fatty acid supplementation on inflammatory and cardiac biomarkers in patients with type 2 diabetes: secondary analyses from a randomised controlled trial. Diabetologia. DOI PubMed
  5. RCTNaeini Z, Toupchian O, Vatannejad A et al. (2020). Effects of DHA-enriched fish oil on gene expression levels of p53 and NF-κB and PPAR-γ activity in PBMCs of patients with T2DM: A randomized, double-blind, clinical trial. Nutr Metab Cardiovasc Dis. DOI PubMed
  6. RCTFayh APT, Borges K, Cunha GS et al. (2018). Effects of n-3 fatty acids and exercise on oxidative stress parameters in type 2 diabetic: a randomized clinical trial. J Int Soc Sports Nutr. DOI PubMed
  7. RCTSiniarski A, Haberka M, Mostowik M et al. (2018). Treatment with omega-3 polyunsaturated fatty acids does not improve endothelial function in patients with type 2 diabetes and very high cardiovascular risk: A randomized, double-blind, placebo-controlled study (Omega-FMD). Atherosclerosis. DOI PubMed
Show 5 more references
  1. RCTElajami TK, Alfaddagh A, Lakshminarayan D et al. (2017). Eicosapentaenoic and Docosahexaenoic Acids Attenuate Progression of Albuminuria in Patients With Type 2 Diabetes Mellitus and Coronary Artery Disease. J Am Heart Assoc. DOI PubMed
  2. RCTPoreba M, Mostowik M, Siniarski A et al. (2017). Treatment with high-dose n-3 PUFAs has no effect on platelet function, coagulation, metabolic status or inflammation in patients with atherosclerosis and type 2 diabetes. Cardiovasc Diabetol. DOI PubMed
  3. RCTToupchian O, Sotoudeh G, Mansoori A et al. (2016). Effects of DHA-enriched fish oil on monocyte/macrophage activation marker sCD163, asymmetric dimethyl arginine, and insulin resistance in type 2 diabetic patients. J Clin Lipidol. DOI PubMed
  4. RCTZheng JS, Lin M, Fang L et al. (2016). Effects of n-3 fatty acid supplements on glycemic traits in Chinese type 2 diabetic patients: A double-blind randomized controlled trial. Mol Nutr Food Res. DOI PubMed
  5. RCTTremblay AJ, Lamarche B, Hogue JC et al. (2016). n-3 Polyunsaturated Fatty Acid Supplementation Has No Effect on Postprandial Triglyceride-Rich Lipoprotein Kinetics in Men with Type 2 Diabetes. J Diabetes Res. DOI PubMed