Does protein raise blood sugar?

For most people, no. A 2024 meta-analysis of 154 feeding comparisons found that adding protein to a carbohydrate meal cut the glucose response by 50% per gram of protein per gram of carbohydrate in adults without diabetes, and by 10% in type 2 diabetes. In type 1 diabetes it went the other way: protein raised the glucose response by 40%, in only 5 comparisons. Over months, a high-protein diet did not change fasting glucose or HbA1c in 13 trials of 1138 people with type 2 diabetes.

Established. Protein eaten with carbohydrate blunts the rise in blood sugar after a meal in people without diabetes and in type 2 diabetes. In the same 2024 meta-analysis it also raised the insulin response, by 56% without diabetes and 76% in type 2 diabetes. These were short feeding tests, and the abstract does not give a certainty rating.

Not for everyone. Type 1 diabetes is the exception. Without your own insulin, protein in a meal can push glucose up 90 to 240 minutes after eating, and the insulin dose has to account for it. The 40% figure rests on 5 comparisons, so its size is uncertain.

What the trials found

Right after a meal

The 2024 meta-analysis pooled acute crossover trials of carbohydrate test meals with and without added protein, from animal, dairy and plant sources. Each gram of protein per gram of available carbohydrate cut the area under the glucose curve by 50% in adults without diabetes and by 10% in type 2 diabetes. In type 1 diabetes the same comparison raised it by 40%.

Whey taken before a meal is the version tested most. In a 2022 meta-analysis of 5 randomized trials in 134 people with mild or well-controlled type 2 diabetes, glucose was 48 mg/dL (2.67 mmol/L) lower at 60 minutes (95% CI 1.72 to 3.62) and 29 mg/dL (1.59 mmol/L) lower at 120 minutes (95% CI 0.28 to 2.91) than with placebo. The authors rated the certainty low, and the lower end of the 2-hour interval is close to no effect.

Over weeks and months

In a 2020 meta-analysis of 13 randomized trials in 1138 people with type 2 diabetes, a high-protein diet changed fasting glucose by -2.3 mg/dL (95% CI -8.3 to 3.4; metric: -0.13 mmol/L, -0.46 to 0.19) and HbA1c by -0.05%, neither significant, against other diets. Insulin resistance, measured as HOMA-IR, was slightly lower.

In a 2023 meta-analysis of 36 randomized trials in 1851 adults, milk protein supplements lowered fasting glucose by 1.83 mg/dL (95% CI 0.38 to 3.28) and left HbA1c unchanged at 0.01% (95% CI -0.14 to 0.16). That is a small change in fasting glucose. A 2026 network meta-analysis of 25 randomized trials in people with diabetes ranked breakfasts with added whey best for HbA1c, and legume-based and low glycemic index breakfasts best for 2-hour glucose. That review searched only two databases.

Long-term risk of diabetes

Across 16 cohort studies of 615,125 adults, people eating the most total protein had a 14% higher relative risk of type 2 diabetes (RR 1.14, 95% CI 1.04 to 1.24), and the most animal protein an 18% higher one (RR 1.18, 95% CI 1.09 to 1.27). Plant protein showed no link (RR 0.98). These are associations, the card gives no absolute risk, and they are about getting diabetes, not about blood sugar after a meal. A 2024 umbrella review for the German Nutrition Society judged the link with total protein possible, and noted that reviews of trials on HbA1c, fasting glucose and fasting insulin do not support a clear biological link.

For the rest of the nutrient, see the protein guide.

Who should be careful

Type 1 diabetes

A 2019 systematic review of 14 small studies in type 1 diabetes found protein eaten alone affected glucose only from 75 g. In a meal with carbohydrate, 12.5 g or more of protein affected glucose, with effects seen from 90 to 240 minutes after eating. A 2021 systematic review of 18 randomized trials found meals high in fat and protein needed an extra 24% to 75% on top of the usual insulin-to-carbohydrate ratio for better glucose.

Not for everyone. Extra insulin carries its own risk. In a 2021 systematic review of insulin pump dosing in type 1 diabetes, additional insulin for high-protein or high-fat meals improved glucose after the meal, and raised the risk of hypoglycemia in 5 of 14 studies. Changing how you dose is a decision to make with your diabetes team, with glucose monitoring.

Diabetic kidney disease

The American Diabetes Association says that in diabetes with kidney disease not yet on dialysis, cutting protein below the recommended 0.8 g per kg of body weight a day does not meaningfully change glucose measures and may raise the risk of malnutrition.

What expert bodies say

The American Diabetes Association's 2019 consensus report says that for a mixed meal with carbohydrate that is high in fat or protein, insulin should not be dosed on carbohydrate counting alone. We used the 2019 report because we could not check the matching sentence in the 2026 Standards of Care word for word. The German Nutrition Society's umbrella review rates the link between total protein and type 2 diabetes risk as possible.

How we searched

What would change this answer

• Larger feeding trials in type 1 diabetes. The 40% rise rests on 5 comparisons, and a bigger set could change its size.
• Long trials that swap animal protein for plant protein and measure HbA1c, to test whether the cohort link with diabetes risk shows up in blood sugar at all.

Sources

1. ev-prbs-01 · Meta-analysis or systematic review · systematic review and meta-analysis of acute controlled feeding trials · n = 154 trial comparisons
   RESULTS: In 154 trial comparisons of animal, dairy, and plant proteins (without diabetes, n = 22, 67, 32, respectively; T2DM, n = 14, 16, 3, respectively), each gram protein per gram available carbohydrate (g/g) reduced the glucose area under the curve (AUC) less in adults with T2DM than in those without diabetes (-10% compared with -50%, P < 0.05) but increased the insulin AUC similarly (+76% compared with +56%).
   
   Who: adults without diabetes, with type 2 or type 1 diabetes, acute crossover trials of carbohydrate test meals with vs without added protein
   Effect: glucose AUC per g protein/g carbohydrate: -50% without diabetes, -10% with T2DM; insulin AUC +56% and +76%
   Certainty: Acute crossover trials; high heterogeneity; GRADE is not given in the abstract.
   J Nutr, 2024 · checked 2026-10-07 · we read the abstract
2. ev-prbs-02 · Meta-analysis or systematic review · systematic review and meta-analysis of acute controlled feeding trials · n = 5 trial comparisons
   In adults with T1DM, protein increased the glucose AUC by 40% (P < 0.05, n = 5).
   
   Who: adults with type 1 diabetes in acute crossover feeding trials
   Effect: glucose AUC +40% (P < 0.05)
   Certainty: Only 5 comparisons. The opposite sign of effect in T1D: without own insulin, protein raises glucose.
   J Nutr, 2024 · checked 2026-10-07 · we read the abstract
3. ev-prbs-03 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 5 RCTs, 134 persons
   Postprandial glycemia was significantly lower at 60 minutes (weighted mean difference: -2.67 mmol/L; 95% confidence interval, -3.62 to -1.72 mmol/L) and 120 minutes (-1.59 mmol/L; -2.91 to -0.28 mmol/L) in WP group than in placebo group.
   
   Who: persons with mild or well-controlled type 2 diabetes, premeal whey protein vs placebo
   Effect: postprandial glucose WMD -48 mg/dL (95% CI -65 to -31; metric: -2.67 mmol/L, -3.62 to -1.72) at 60 min; -29 mg/dL (-52 to -5; metric: -1.59 mmol/L, -2.91 to -0.28) at 120 min
   Certainty: Authors: the certainty of the evidence is not high; only mild or controlled T2D.
   Nutr Res, 2022 · checked 2026-10-07 · we read the abstract
4. ev-prbs-04 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 13 studies, 1138 patients
   Glycemic control was not significantly different between the high-protein diet and control group, with the changes in fasting plasma glucose (FPG) (-0.13 (95% CI (-0.46, 0.19), p = 0.43) mmol/L) and HbA1c% (-0.05 (95% CI (-0.18, 0.08, p = 0.92))) from baseline to the end of intervention.
   
   Who: T2DM patients in randomized trials comparing a high-protein diet with other diets
   Effect: fasting plasma glucose -2.3 mg/dL (95% CI -8.3 to 3.4; metric: -0.13 mmol/L, -0.46 to 0.19); HbA1c -0.05% (-0.18 to 0.08); HOMA-IR -0.27 (-0.47 to -0.06)
   Certainty: Long-term diet: protein neither raises nor lowers glycemia; insulin resistance is slightly better.
   Clin Nutr, 2020 · checked 2026-10-07 · we read the abstract
5. ev-prbs-05 · Meta-analysis or systematic review · GRADE-assessed systematic review and dose-response meta-analysis of RCTs · n = 36 RCTs, 1851 participants
   It was displayed that supplementation with MP effectively reduced levels of fasting blood glucose (FBG) (weighted mean difference (WMD): -1.83 mg/dL, 95% CI: -3.28, -0.38; P = 0.013), fasting insulin (WMD: -1.06 uU/mL, 95% CI: -1.76, -0.36; P = 0.003), and homeostasis model assessment of insulin resistance (HOMA-IR) (WMD: -0.27, 95% CI: -0.40, -0.14; P < 0.001) while making no remarkable changes in serum hemoglobin A1c (HbA1c) values (WMD: 0.01%, 95% CI: -0.14, 0.16; P = 0.891).
   
   Who: adults in RCTs of milk protein or whey supplementation
   Effect: fasting blood glucose WMD -1.83 mg/dL (95% CI -3.28 to -0.38); fasting insulin -1.06 uU/mL; HbA1c 0.01% (-0.14 to 0.16)
   Certainty: Clinically small effect (1.83 mg/dL ≈ 0.1 mmol/L).
   Nutr J, 2023 · checked 2026-10-07 · we read the abstract
6. ev-prbs-06 · Meta-analysis or systematic review · systematic review and network meta-analysis of RCTs · n = 25 RCTs
   Subgroup analyses showed that legume-based breakfasts and low-glycemic-index breakfasts were most effective in reducing 2-hour postprandial blood glucose, while breakfasts supplemented with whey protein were most effective in improving HbA1c.
   
   Who: patients with diabetes mellitus in RCTs comparing breakfast macronutrient compositions
   Effect: modified breakfast vs standard: 2-h glucose MD -34 mg/dL (95% CI -44 to -24; metric: -1.90 mmol/L, -2.46 to -1.34), HbA1c MD -0.52%; whey-supplemented breakfasts ranked best for HbA1c
   Certainty: Search up to March 2026, PubMed and WoS only; different breakfast compositions pooled.
   Front Endocrinol (Lausanne), 2026 · checked 2026-10-07 · we read the abstract
7. ev-prbs-07 · Observational data · systematic review and dose-response meta-analysis of prospective cohorts · n = 16 cohort studies, 615,125 participants, 52,342 T2D cases
   Intakes of total (pooled effect size: 1.14, 95% CI: 1.04-1.24) and animal (pooled effect size: 1.18, 95% CI: 1.09-1.27) protein were associated with an increased risk of T2D.
   
   Who: adults in prospective cohort studies, highest vs lowest protein intake
   Effect: total protein RR 1.14 (95% CI 1.04 to 1.24); animal protein RR 1.18 (1.09 to 1.27); plant protein 0.98 (0.89 to 1.08)
   Certainty: Observational data, risk of T2D, not postprandial glucose; RCTs do not confirm this link with glycemia (37718370).
   Clin Nutr, 2024 · checked 2026-10-07 · we read the abstract
8. ev-prbs-08 · Observational data · umbrella review of systematic reviews (AMSTAR 2, NutriGrade) · n = 8 systematic reviews
   However, SRs on RCTs examining major glycaemic traits (HbA1c, fasting glucose, fasting insulin) do not support a clear biological link with T2D risk.
   
   Who: systematic reviews of randomized trials and cohort studies on protein intake and T2D risk, 2009 to 2022
   Effect: cohort RR 1.09 to 1.11 for total protein; RCT reviews of HbA1c, fasting glucose and insulin do not support a clear link
   Certainty: The basis for the DGE guideline; certainty "possible".
   Eur J Nutr, 2024 · checked 2026-10-07 · we read the abstract
9. ev-prbs-09 · Observational data · systematic review (mixed designs, no meta-analysis) · n = 14 studies
   When protein was consumed alone a glycaemic effect was not seen until ≥ 75 g. In a carbohydrate-containing meal ≥ 12.5 g of protein impacted the postprandial glucose.
   
   Who: individuals with type 1 diabetes, protein alone (2 studies) or in mixed meals (12 studies)
   Effect: protein alone: glycemic effect from >= 75 g; with carbohydrate: from >= 12.5 g; timing 90 to 240 min; fat amplified the rise
   Certainty: Small studies 1992-2018; late hyperglycemia is the reason protein is counted in the insulin dose in T1D.
   Diabet Med, 2019 · checked 2026-10-07 · we read the abstract
10. ev-prbs-10 · Meta-analysis or systematic review · systematic review of RCTs · n = 18 studies
    CONCLUSIONS: Findings highlight the glycaemic benefit of an additional 24%-75% ICR for fat and fat and protein meals.
    
    Who: people with type 1 diabetes in RCTs of insulin strategies for fat and fat-plus-protein meals
    Effect: glycemic benefit with additional 24% to 75% of the insulin-to-carbohydrate ratio; at least 60% upfront, 15 min before the meal
    Certainty: It records the insulin requirement, not a safe dose; individual titration under CGM.
    Diabet Med, 2021 · checked 2026-10-07 · we read the abstract
11. ev-prbs-11 · Observational data · systematic review (no meta-analysis due to heterogeneity) · n = 7 high-protein studies, 129 participants; 11 high-fat studies, 234 participants
    Additional insulin further improved postprandial glycaemia, although increasing risk of hypoglycaemia in 5 of 14 studies.
    
    Who: adults and children with type 1 diabetes on insulin pump therapy; 7 studies of high-protein meals (129 participants)
    Effect: dual-wave bolus superior; additional insulin raised hypoglycemia risk in 5 of 14 studies
    Certainty: Interaction with insulin: an extra bolus risks hypoglycemia, hence "with caution" and with CGM.
    Diabetes Res Clin Pract, 2021 · checked 2026-10-07 · we read the abstract
12. ev-prbs-12 · Position of an expert body · consensus report · n = —
    When consuming a mixed meal that contains carbohydrate and is high in fat and/or protein, insulin dosing should not be based solely on carbohydrate counting.
    
    Who: adults with diabetes on insulin
    Effect: consensus recommendation
    Certainty: ADA consensus 2019; Standards of Care 2026 not verified verbatim (see log).
    Evert AB et al., Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report (American Diabetes Association), Diabetes Care, 2019 · checked 2026-10-07 · we read the fulltext
13. ev-prbs-13 · Position of an expert body · consensus report · n = —
    In individuals with diabetes and non–dialysis-dependent diabetic kidney disease (DKD), reducing the amount of dietary protein below the recommended daily allowance (0.8 g/kg body weight/day) does not meaningfully alter glycemic measures, cardiovascular risk measures, or the course of glomerular filtration rate decline and may increase risk for malnutrition.
    
    Who: individuals with diabetes and non-dialysis-dependent diabetic kidney disease
    Effect: protein below RDA 0.8 g/kg/day: no meaningful change in glycemic measures or GFR decline; possible malnutrition
    Certainty: Consistent with Cochrane 2023 (36594428): low-protein diet in CKD, effect on the kidneys is uncertain.
    Evert AB et al., Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report (American Diabetes Association), Diabetes Care, 2019 · checked 2026-10-07 · we read the fulltext