Is metformin made from fish, and are there any interactions with fish oil supplements?

Short Answer

Metformin is not made from fish; it is a synthetic drug in the biguanide class that was developed from a compound found in the plant Galega officinalis (French lilac), not from animal sources. ^{[1] [2]} There are no known direct drug–drug interactions between metformin and fish oil (omega-3 fatty acids), and they are commonly taken together; however, omega-3s can slightly prolong bleeding time, so caution is reasonable if you also use anticoagulants or have bleeding risks. ^{[3] [4] [5]}

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What Metformin Is Made Of

• Synthetic biguanide: Metformin hydrochloride is a chemically synthesized antihyperglycemic agent; its chemical name is N,N-dimethylimidodicarbonimidic diamide hydrochloride. ^{[1] [6]}
• Not related to other oral diabetes classes: It is not chemically or pharmacologically related to sulfonylureas, thiazolidinediones, or alpha-glucosidase inhibitors. ^{[1] [7]}
• Herbal origin of the idea, not the pill: The drug’s development traces back to galegine, a guanidine derivative from the French lilac plant, but modern metformin tablets are manufactured synthetically and are not derived from fish or other animal products. ^{[2] [8]}

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Metformin and Fish Oil: Interactions and Safety

• No direct interaction identified: Standard drug interaction data for metformin do not list omega-3/fish oil as interacting with metformin, and metformin’s pharmacokinetics are unchanged with many common co-medications. ^{[3] [9]}
• Bleeding considerations with omega-3s: Omega-3 ethyl esters have been shown to prolong bleeding time modestly in some trials, typically within normal limits and without clinically significant bleeding episodes, but caution is advised when combined with anticoagulants. ^[4]
• Co-use in metabolic care: Omega-3 long-chain polyunsaturated fatty acids are widely used to improve cardiometabolic risk factors and generally do not adversely interact with common therapies for diabetes, hypertension, and dyslipidemia. ^[5]

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Potential Benefits When Used Together

• Triglyceride reduction with omega-3s: Fish oil (EPA/DHA) consistently lowers triglycerides, which can complement metformin’s glucose-lowering effects. ^[5]
• Metabolic improvements: In clinical contexts, omega-3s can improve triglycerides and sometimes insulin resistance, while metformin improves glycemic control and lipid parameters such as HDL and LDL in certain groups. ^{[10] [5]}
• No glycemic worsening at typical doses: Concerns about worsened blood sugar with high-dose fish oil have been eased by more recent studies; typical supplemental doses focus on triglyceride lowering without harming glycemic control. ^[5]

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Practical Tips for Safe Use

• Take metformin with meals: This can reduce common gastrointestinal side effects like nausea or diarrhea. ^[11]
• Monitor bleeding risk: If you are on blood thinners (e.g., warfarin) or have bleeding disorders, discuss omega-3 dosing with your clinician due to its mild effect on bleeding time. ^[4]
• Keep a medication list: Share all prescription drugs, over-the-counter medicines, vitamins, and supplements (including fish oil) with your healthcare provider. ^[12]

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Key Facts at a Glance

• Metformin source: Synthetic; inspired by a plant compound, not fish. ^{[1] [2]}
• Mechanism category: Biguanide antihyperglycemic agent, distinct from other oral diabetes medications. ^{[1] [7]}
• Fish oil interaction: None known with metformin; watch bleeding risk if on anticoagulants. ^{[3] [4] [5]}
• Cardiometabolic role of omega-3s: Beneficial for triglycerides and may support overall heart health. ^[5]

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References

• Metformin drug descriptions and chemistry. ^{[1] [6] [13] [7]}
• Metformin pharmacokinetic and historical context. ^{[2] [8]}
• Metformin interaction profiles. ^{[3] [12] [9] [14]}
• Omega-3 bleeding precautions and clinical role. ^{[4] [5]}
• Clinical observations on omega-3s and metabolic parameters. ^{[10] [5]}