Does fish oil help with diabetes? What the research does and doesn't show

The evidence doesn't support fish oil as a way to control blood sugar. The largest meta-analysis on the topic found improvements in fasting glucose and insulin resistance across pooled trials, but a separate, more tightly controlled Cochrane review of people specifically diagnosed with type 2 diabetes found no effect on blood sugar, glycated hemoglobin, or fasting insulin at all.

What the evidence doesn't support

It doesn't support fish oil as something that lowers A1C or reverses insulin resistance in people already diagnosed with type 2 diabetes — the most tightly controlled trial data in that specific population found no measurable change in blood sugar control. It doesn't support one dose as clearly established either; the studies below range from under 1,000 mg to 3.5 grams a day of combined EPA and DHA.

What the trials found

A 2022 systematic review and meta-analysis in Critical Reviews in Food Science and Nutrition pooled 30 studies on omega-3 supplementation and markers related to diabetes. Almost 70% of the included studies (20 of 30) found at least one significant effect. In the pooled meta-analysis specifically, omega-3 was associated with a reduction in fasting blood glucose and in insulin resistance, but showed no significant effect on glycated hemoglobin (HbA1c) — the longer-term blood sugar marker doctors actually use to track diabetes control.

A 2008 Cochrane review took a narrower, more tightly controlled look: 23 randomized controlled trials in 1,075 people specifically diagnosed with type 2 diabetes, mean dose 3.5 grams a day for a mean of 8.9 weeks. That review found no significant change in HbA1c, fasting glucose, or fasting insulin — omega-3's measurable effect in this population was on triglycerides and VLDL cholesterol going down, not blood sugar control.

In women with polycystic ovary syndrome (PCOS) — a condition closely tied to insulin resistance — a 2023 meta-analysis of 11 randomized trials in 816 patients found omega-3 supplementation reduced fasting glucose, fasting insulin, and a standard insulin-resistance score (HOMA-IR), alongside reductions in waist circumference and several lipid measures. The benefit was more consistent in trials lasting longer than 8 weeks, regardless of the specific dose used.

Questions people ask

Is omega-3 good for diabetes?

It depends on which measure you mean. A large pooled analysis found improvements in fasting glucose and insulin resistance markers, but the most tightly controlled review of people diagnosed with type 2 diabetes found no change in HbA1c — the marker doctors use to judge actual blood sugar control over time.

How much fish oil should a diabetic take?

There isn't an established dose for this specific use. The trials above range from under 1,000 mg to 3.5 grams a day of combined EPA and DHA, and the Cochrane review at the higher end of that range found no blood sugar benefit at all — so a higher dose isn't obviously the answer either. Anyone with diagnosed diabetes should work out dosing with the doctor managing their care, not from a range of trial doses.

Can a diabetic take fish oil?

The trials above didn't report safety concerns specific to people with diabetes taking omega-3, beyond the general side effects covered on the fish oil side effects page. Anyone who takes medication for diabetes should still confirm with their doctor before adding a new supplement.

Is omega-3 good for PCOS?

A 2023 meta-analysis of 11 trials in women with PCOS found improvements in fasting glucose, fasting insulin, and insulin resistance scores, alongside reductions in waist circumference and several lipid measures — one of the more consistent positive findings across the research reviewed here.

When to talk to a doctor

Diagnosed diabetes, prediabetes, or PCOS call for a doctor's ongoing management, not a supplement swapped in for medication or monitoring. Fish oil is not a treatment for diabetes or insulin resistance, and nothing in the evidence above supports using it in place of prescribed diabetes care. If you take insulin or another diabetes medication, or are pregnant or nursing, talk to a doctor before adding any supplement.

Related reading: fish oil and cholesterol: what the research does and doesn't show, fish oil and weight loss: what the research does and doesn't show, how much fish oil should you take a day, and fish oil and medications: what to check.