Based on NIH | Do I need to adjust my metformin dose or take any special precautions when eating shrimp or other shellfish?

There is no known interaction between metformin and shrimp or other shellfish, and you generally do not need to adjust your metformin dose when eating seafood. Metformin’s absorption can be modestly affected by food in general, but this does not require dose changes and is usually managed by taking metformin with meals to reduce stomach side effects. ^[1] Metformin’s official labeling outlines many drug interactions and precautions, and none relate specifically to shellfish or seafood. ^{[2] [3]}

Metformin and Food

• Food can slightly lower and delay metformin absorption, which is expected and not harmful. ^[1] Taking metformin with meals is commonly recommended because it helps reduce gastrointestinal upset like nausea or diarrhea. ^[4]

Shellfish Allergy vs. Iodine Myth

• Metformin has a contraindication for people with a known hypersensitivity to metformin itself, but shellfish allergy is not listed as a concern or contraindication. ^{[5] [6]} If you have a shellfish allergy, you can still take metformin; shellfish allergy does not imply an allergy to metformin or to iodinated contrast used in imaging.

When to Pause or Adjust Metformin

While shellfish does not require dose changes, there are situations related to illness and hydration where temporary precautions are advised:

• Severe vomiting, diarrhea, fever, or poor fluid intake (dehydration): you may need to stop metformin briefly and restart once you are well and hydrated, because dehydration can raise the risk of rare complications. ^{[7] [8]}
• Surgery or imaging with iodinated contrast: metformin is typically stopped temporarily and restarted after kidney function is confirmed. ^{[5] [9]}
• Alcohol: avoid heavy alcohol use because it can increase metformin’s effect on lactate. ^[10]

Vitamin B12 Consideration

Long‑term metformin use can be associated with lower vitamin B12 levels in some people, which is usually reversible and may be managed with supplementation. ^[11] Monitoring blood counts yearly, and checking vitamin B12 every 2–3 years in at‑risk individuals, is often reasonable. ^{[12] [13]}

Gastrointestinal Side Effects

The most common metformin side effects are gastrointestinal (diarrhea, nausea), and taking the medicine with food often helps. ^[4] These effects are patient‑specific and usually diminish over time. ^[14]

Bottom Line

• No dose adjustment is needed when eating shrimp or other shellfish. ^{[2] [3]}
• Take metformin with meals to improve tolerability; general food intake can slightly lower peak levels but does not require changing the dose. ^[1]
• Use standard precautions during dehydration, severe illness, surgery, or contrast imaging, and consider periodic vitamin B12 monitoring with long‑term use. ^{[7] [8] [5] [9] [11] [12]}

If you’d like help tailoring these precautions to your health status (kidney function, alcohol intake, or upcoming procedures), feel free to share more details.