Which fish is not good for diabetics? (and why)

November 19, 2025 •

3 min read

According to the American Diabetes Association, eating fish twice a week is beneficial for heart health, but not all fish and preparation methods are created equal. Knowing which fish is not good for diabetics is crucial for managing blood sugar and avoiding complications. Certain species and preparations can actually increase health risks due to high mercury levels, unhealthy fats, or excessive sodium.

Quick Summary

The guide explains why some fish are unsuitable for people with diabetes, citing high mercury content, inflammatory omega-6 ratios, and processed additives. It details which specific fish species and preparations to avoid, offering healthier alternatives and cooking methods to support diabetes management. The information covers making informed choices for heart health and blood sugar control.

Key Points

Avoid high-mercury species: Large predatory fish like shark, swordfish, and king mackerel accumulate high levels of mercury, which is harmful for diabetics.
Limit fried and processed fish: Frying adds unhealthy fats and calories that can spike blood sugar. Processed fish products are often high in sodium, raising blood pressure concerns.
Beware of unhealthy omega-6 ratios: Some farmed fish, particularly tilapia, can have an unfavorable omega-6 to omega-3 ratio, which promotes inflammation.
Opt for high omega-3, low-mercury options: Excellent choices include salmon, sardines, trout, and cod, which offer heart-protective benefits.
Choose healthy cooking methods: Baking, grilling, steaming, or broiling are the best ways to prepare fish to retain its nutritional value without adding unhealthy fats.
Always read labels for canned products: For canned fish, select water-packed, low-sodium varieties to avoid hidden salt and fat.
Mindful consumption supports heart health: Careful selection and preparation ensure fish contributes positively to managing diabetes and reducing cardiovascular risk.

Understanding the Risks: Mercury and Contaminants

For individuals with diabetes, who already face a higher risk of cardiovascular issues, consuming fish with elevated mercury levels poses a significant health concern. Mercury can accumulate in larger, longer-living predatory fish, and its consumption has been linked to increased risk of type 2 diabetes and other health problems. It is not the fish itself but the contaminants it may contain that pose a risk. The U.S. Food and Drug Administration (FDA) provides guidelines on limiting mercury in fish consumption, especially for vulnerable groups like those with chronic conditions.

High-Mercury Fish to Avoid

Shark: A large, long-lived predator at the top of the food chain, it has very high mercury levels.
Swordfish: Another large predatory fish that accumulates significant amounts of mercury over its lifespan.
King Mackerel: Also known as kingfish, this species is high in mercury and should be limited.
Tilefish (Gulf of Mexico): This specific variety is known for particularly high mercury concentrations.
Bigeye Tuna: Unlike smaller, canned varieties, bigeye tuna is larger and has a higher mercury content.
Marlin: A large, ocean-dwelling fish with mercury levels that make it unsuitable for regular consumption.
Orange Roughy: A very long-lived species, allowing mercury to build up extensively.

The Problem with Fried and Heavily Processed Fish

While fish is a lean protein source, the preparation method can completely undermine its health benefits for a person with diabetes. Deep-frying fish, especially with starchy breading, adds unhealthy fats and carbohydrates that can cause a blood sugar spike and raise cholesterol levels. Processed fish, such as certain canned varieties or fish sticks, often contains high levels of sodium, which can contribute to high blood pressure, a common comorbidity for those with diabetes. A study published in the journal Springer showed a correlation between fried fish and shellfish consumption and higher type 2 diabetes incidence.

Unhealthy Omega Ratios: The Tilapia Controversy

Omega-3 and omega-6 fatty acids are both important, but a balanced ratio is crucial for controlling inflammation. An unhealthy balance, with too much omega-6, can increase inflammation, which is particularly problematic for diabetics. While many fish, like salmon and sardines, have a beneficial omega-3 to omega-6 ratio, some, like farmed tilapia, have an unfavorable ratio. This is a concern because chronic inflammation can aggravate conditions like heart disease and negatively impact insulin sensitivity.

Comparison of Healthy vs. Unhealthy Fish Choices for Diabetics


Feature	Better Choices (e.g., Salmon, Sardines, Trout)	Worse Choices (e.g., Shark, Fried Tilapia)
Mercury Content	Low to moderate	Very high
Omega Fatty Acid Ratio	Favorable (high omega-3)	Unfavorable (high omega-6 in farmed)
Recommended Serving	Twice weekly	Limit to rare occasions or avoid
Cooking Method	Baked, grilled, steamed, broiled	Fried, breaded, heavily sauced
Fat Type	Healthy omega-3s	Unhealthy trans and saturated fats (if fried)
Sodium Level	Low (if fresh)	High (especially if processed)
Impact on Inflammation	Anti-inflammatory	Pro-inflammatory (unhealthy omega ratio)

Making Smarter Seafood Choices

To ensure fish remains a healthy part of a diabetes management plan, focus on low-mercury, high-omega-3 options like salmon, sardines, and trout. Always prioritize healthy cooking methods such as baking, grilling, steaming, or poaching to avoid adding unnecessary fats and calories. When choosing canned fish, opt for water-packed and low-sodium varieties. Reading nutrition labels is key for all processed products. By understanding which types of fish and preparations to avoid, individuals with diabetes can safely enjoy seafood and benefit from its nutritional value without compromising their health goals. For more detailed dietary guidance, consulting a healthcare provider or a registered dietitian is always recommended. The American Heart Association offers extensive resources on incorporating heart-healthy foods, including fish, into a balanced diet.

Conclusion: Prioritize Safety and Preparation

While fish is widely promoted as a healthy food, especially for its protein and omega-3 content, diabetics must exercise caution in their selection and preparation. Avoiding large, predatory fish high in mercury and steering clear of fried or heavily processed options are essential steps for protecting heart health and maintaining stable blood sugar. By choosing smaller, oily fish and preparing them in simple, healthy ways, people with diabetes can maximize the benefits of seafood while mitigating potential risks. Informed choices regarding fish consumption are a valuable part of comprehensive diabetes management.

Frequently Asked Questions

Yes, people with diabetes can eat many types of fish, as it is a great source of lean protein and omega-3 fatty acids. However, it is crucial to avoid fish high in mercury and unhealthy fats, and to choose healthy preparation methods.

Mercury, found in certain large fish, can be harmful if consumed excessively. For diabetics, who are already at a higher risk of heart disease, excessive mercury intake adds another health risk factor and has been linked to type 2 diabetes development.

While tilapia is a lean, high-protein fish, some farmed varieties have an unfavorable omega-6 to omega-3 fatty acid ratio, which can increase inflammation. It is best to choose fish with a higher omega-3 content, like salmon or cod.

The healthiest cooking methods are baking, grilling, steaming, or broiling. These techniques avoid adding unnecessary fats and calories that come with deep-frying or using buttery sauces.

Yes, canned tuna and salmon can be safe and healthy options. It is best to choose varieties that are packed in water and labeled as low-sodium to avoid excess salt and oil.

Fatty fish like salmon, sardines, and mackerel are particularly rich in omega-3 fatty acids, which are beneficial for heart health and can help reduce inflammation.

The American Diabetes Association recommends consuming at least two servings of fish per week, with a focus on fatty fish for their omega-3 benefits.