Keto vs. Low-Carb vs. Mediterranean vs. Carnivore: Which Is Best for Blood Sugar?

Evidence: Moderate

Mediterranean, low-carb, keto, carnivore: each has passionate fans who say it’s the best diet for blood sugar. So we compared all four on what matters most: the evidence for blood sugar, how easy they are to stick with, and the trade-offs.

Best diet for blood sugar: quick comparison

Diet	Carbs	Evidence for blood sugar	Ease of sticking with it	Main watch-outs
Mediterranean	Moderate	Strong	Easier	Portion sizes of grains and starches
Low-carb	Under 130 g a day	Moderate to strong	Moderate	Medication adjustments; benefits fade if you stop
Keto	Under about 50 g a day	Moderate	Harder	Higher LDL cholesterol, low fiber, hard to sustain
Carnivore	Near zero	Early	Hardest	Higher LDL cholesterol, no fiber, nutrient gaps

Mediterranean

What it is: vegetables, fruit, legumes, whole grains, nuts and olive oil, with fish and poultry as the main proteins, plus limited red meat and sweets.

The evidence: it’s one of the most-studied eating patterns in the world, and the ADA’s 2026 guidelines name it, together with low-carb, as one of the best-supported options for preventing type 2 diabetes. In addition, it has strong evidence for heart health, which matters because heart disease is the leading complication of diabetes.

Best for: people who want a flexible, family-friendly approach they can follow for life.

Low-carb

What it is: generally under 130 grams of carbohydrate a day, built around vegetables, protein and healthy fats, with small amounts of starch and fruit.

The evidence: a 2021 BMJ review of 23 trials found that after six months, 57% of people with type 2 diabetes on low-carb diets had an HbA1c under 6.5%, compared with 31% on comparison diets. Similarly, weight, triglycerides and insulin sensitivity improved, though the advantage shrank by 12 months. Read more in Low-Carb Eating and Blood Sugar.

Best for: people who want faster blood sugar improvements and don’t mind planning meals around protein and vegetables.

Keto

What it is: a very-low-carb diet, usually 20–50 grams a day, low enough that the body shifts to burning fat and producing ketones.

The evidence: the best head-to-head test is the 2022 Keto-Med trial from Stanford. Forty adults with prediabetes or type 2 diabetes ate a well-formulated keto diet for 12 weeks and a Mediterranean-style diet for 12 weeks, in random order. Importantly, both diets cut added sugar and refined grains. The results:

• Blood sugar (HbA1c) improved on both diets, with no meaningful difference between them.
• Triglycerides fell more on keto (−16% vs. −5%).
• LDL cholesterol rose 10% on keto but fell 5% on the Mediterranean diet.
• Weight loss was similar (8% vs. 7%).
• Keto provided less fiber, folate, vitamin C and magnesium.
• After the study, participants’ eating looked more like the Mediterranean diet, suggesting it was easier to keep up.

Best for: people who want the most aggressive carb cut, ideally with medical supervision and cholesterol monitoring.

Carnivore

What it is: animal foods only, with no plants at all.

The evidence: a 2026 review found only nine studies, mostly surveys and case reports, with no controlled trials. Admittedly, some people report better blood sugar, but LDL cholesterol rose sharply on average in the two largest studies, and modeled meal plans provided under 1 gram of fiber a day. Full details: Carnivore Diet: What the Evidence Actually Says.

Best for: honestly, it’s hard to recommend for blood sugar when less restrictive options work as well with more evidence.

What every good diet for blood sugar has in common

Look closely, and you’ll see the diets that work share three habits: plenty of non-starchy vegetables, very little added sugar, and few refined grains. In fact, the Keto-Med researchers credited these shared features for why both diets improved blood sugar. In other words, if you get those three right, you’ve captured most of the benefit, whichever label you choose.

How to choose the best diet for blood sugar

• Want something sustainable for the whole family? Start with Mediterranean, minus the sugary drinks and white bread.
• Want faster blood sugar results? Try moderate low-carb (under 130 g a day) and adjust from there.
• Considering keto? Do it with your doctor, check your cholesterol after a few months, and keep plenty of vegetables.
• Not sure how your body responds? If you have diabetes, a continuous glucose monitor (CGM) can show which meals spike your blood sugar. The ADA’s 2026 guidelines expanded their recommendation for CGM use in people with diabetes.

Talk to your doctor before cutting carbs if you take diabetes medication. Lowering carbohydrates quickly can cause low blood sugar if you use insulin or certain other glucose-lowering drugs, and very-low-carb eating should be avoided with SGLT2 inhibitors (such as empagliflozin or dapagliflozin) because of the risk of ketoacidosis. Your doses may need adjusting, sometimes within days.

The bottom line

There’s no single best diet for blood sugar that suits everyone, but there is a best approach: cut added sugar and refined carbs, eat more vegetables, and pick a pattern you can live with. Overall, Mediterranean and low-carb have the strongest evidence, keto works but has trade-offs, and carnivore is still largely unproven.

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This article is for general education and isn’t medical advice. See our medical disclaimer.

Sources

1. American Diabetes Association. Prevention or Delay of Diabetes and Associated Comorbidities: Standards of Care in Diabetes—2026. Diabetes Care. 2026;49(Suppl 1):S50–S60. PMC.
2. American Diabetes Association. Standards of Care in Diabetes—2026 (press release). diabetes.org.
3. Goldenberg JZ, et al. Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission: systematic review and meta-analysis. BMJ. 2021;372:m4743. PMC.
4. Gardner CD, et al. Effect of a ketogenic diet versus Mediterranean diet on glycated hemoglobin in individuals with prediabetes and type 2 diabetes: the Keto-Med randomized crossover trial. Am J Clin Nutr. 2022;116(3):640–652. PubMed.
5. Lietz A, Dapprich J, Fischer T. Carnivore Diet: A Scoping Review of the Current Evidence, Potential Benefits and Risks. Nutrients. 2026;18:348. PMC.
6. Della Corte K, et al. Dietary Sugar Intake and Incident Type 2 Diabetes Risk: A Dose-Response Meta-Analysis. Adv Nutr. 2025;16(5):100413. PubMed.