The keto diet and diabetes relationship is one of the most actively researched areas in modern nutrition science. For people with type 2 diabetes in particular, the evidence is striking: carbohydrate restriction that produces sustained ketosis has been shown in multiple randomised controlled trials to significantly reduce blood glucose, lower HbA1c, reduce medication requirements, and in some cases produce clinical remission of type 2 diabetes altogether. These are not marginal or speculative findings. They are the consistent output of the highest-quality dietary research currently available.
The picture for type 1 diabetes is more complex, more individual, and more dependent on active medical supervision. The picture for type 2 diabetes is clearer and increasingly reflects mainstream clinical guidance rather than fringe dietary thinking.This article covers what the research shows about keto and blood sugar management, the clinical evidence for keto and type 2 diabetes remission, the specific risks and requirements for people with type 1 diabetes, and the practical monitoring that anyone with diabetes needs in place before and during a ketogenic diet. For the foundational dietary framework, see the complete keto diet plan.
How the Keto Diet Affects Blood Sugar Levels
Blood glucose levels are directly controlled by dietary carbohydrate intake. Every gram of carbohydrate you eat is converted to glucose in the digestive process. Reducing carbohydrate intake reduces the amount of glucose entering the bloodstream after meals, which reduces the insulin response required to manage that glucose, and which reduces the overall blood glucose burden that the pancreas and insulin-sensitive tissues are dealing with throughout the day.
On a standard ketogenic diet, carbohydrate intake is reduced to 20 to 50 grams of net carbs per day. This dramatically reduces post-meal glucose spikes, reduces fasting glucose over time, and reduces average blood glucose as measured by HbA1c. These effects are measurable within days to weeks of starting a ketogenic diet and compound over months of consistent adherence.
A meta-analysis of randomised controlled trials published in PMC(Zhou et al., Nutrients, 2022) examining ketogenic diet effects in overweight patients with type 2 diabetes found that the ketogenic diet significantly reduced fasting blood glucose, HbA1c, LDL cholesterol, and BMI compared to control diets, while significantly increasing HDL cholesterol. The HbA1c reduction was statistically significant and clinically meaningful.[1]The blood sugar response to keto is relevant not only to people with diagnosed diabetes. Anyone with prediabetes, insulin resistance, metabolic syndrome, or elevated fasting glucose will see significant improvements in these markers from sustained carbohydrate restriction. Keto and insulin resistance is covered in more depth in the dedicated guide on keto diet and insulin resistance.
Ketogenic Diet and Type 2 Diabetes: What the Research Shows
The evidence base for keto and type 2 diabetes is now substantial enough that several national diabetes associations, including Diabetes UK and the American Diabetes Association, have formally acknowledged very low-carbohydrate and ketogenic diets as viable therapeutic options for type 2 diabetes management.
Type 2 diabetes remission on keto: what the research shows
A 2025 systematic review published in PMC (Das et al., Cureus, 2025) evaluated the long-term efficacy and safety of low-carbohydrate and ketogenic diets in type 2 diabetes remission across six studies with follow-up durations of one to eight years. The findings are significant: remission rates were highest at one year, reaching up to 62 percent of participants, with a meaningful proportion maintaining remission over longer periods. The review found significant reductions in HbA1c, body weight, BMI, and systolic blood pressure across all included studies. [2]
The Unwin et al. 2023 study included in that review, which followed patients for eight years, demonstrated a reduction in HbA1c from 63 to 46 mmol/mol in the intervention group, representing a shift from diabetic to near-normal blood glucose levels sustained over nearly a decade. This is the type of outcome that pharmacological treatment rarely achieves with equivalent consistency.
HbA1c improvements: the clinical picture
HbA1c is the primary clinical measure of blood glucose control over a three-month period. A reduction in HbA1c of 1 percent (or 11 mmol/mol) is considered clinically significant in diabetes management. Multiple randomised controlled trials and systematic reviews show that keto consistently produces HbA1c reductions well above this clinical threshold.
A 2022 systematic review and meta-analysis published in PMC (Alluwyam and Estrella, 2022) examining ketogenic versus low-carbohydrate diets on glycaemic control found a significant decrease in HbA1c percentage in patients consuming ketogenic diets compared to control diets (standardised mean difference: -1.45%, 95% CI: -2.73%, -0.17%, P < 0.00001). [3] This is not a marginal effect. It represents a level of glycaemic improvement that typically requires multiple medications to achieve through pharmacological means.
Medication reduction: a critical safety consideration
When keto reduces blood glucose rapidly and significantly, diabetes medications that work by lowering blood glucose, particularly insulin, sulphonylureas such as gliclazide and glibenclamide, and SGLT2 inhibitors such as empagliflozin, can cause blood glucose to fall too low. Hypoglycaemia in a person who has not had their medication adjusted is a medical emergency.
This is the central reason why anyone with type 2 diabetes who is on medication must work with their GP or diabetes team when starting keto. The diet works. That is precisely why medication must be adjusted proactively rather than reactively. Many people starting keto and type 2 diabetes management find their medication needs reduce significantly or disappear entirely within weeks. This outcome requires medical supervision to manage safely, not because keto is dangerous, but because it works rapidly.
| If you are on diabetes medication and starting ketoTell your GP or diabetes nurse before you start. Ask for a plan to monitor blood glucose daily, particularly in the first two weeks. Ask which of your medications carry a risk of hypoglycaemia on a very low-carbohydrate diet. Do not reduce your own medication without medical guidance. Hypoglycaemia from unmanaged insulin or sulphonylurea doses is a medical emergency. |
Keto and Type 1 Diabetes: A More Complex Picture
The situation for type 1 diabetes and keto is fundamentally different from type 2 diabetes. Type 1 diabetes is an autoimmune condition in which the pancreas produces no insulin. Without external insulin administration, ketone levels can rise uncontrollably because there is no insulin to suppress overproduction, leading to diabetic ketoacidosis, a life-threatening emergency. This is categorically different from nutritional ketosis in a person with intact insulin function.
However, many people with type 1 diabetes do follow ketogenic diets, and some do so with excellent results in terms of blood glucose stability. The key characteristics of this population are:
| Continuous glucose monitoring throughout.People with type 1 diabetes on keto need to check glucose frequently, ideally using a continuous glucose monitor, because the diet can change insulin requirements significantly and unpredictably, particularly during early adaptation.Significant insulin dose adjustment.Carbohydrate reduction on keto dramatically reduces the mealtime insulin requirements of a person with type 1 diabetes. Bolus insulin doses must be recalculated by a diabetes care team. Background insulin doses may also need adjustment as insulin sensitivity improves.Knowledge of the signs of DKA.People with type 1 diabetes on keto must be able to recognise the symptoms of diabetic ketoacidosis: severe nausea and vomiting, abdominal pain, fruity-smelling breath that is different from normal keto breath, and blood ketone readings above 3.0 mmol/L combined with elevated blood glucose. |
The research on type 1 diabetes and keto is less extensive than for type 2, but the available evidence suggests that well-managed keto can significantly improve time-in-range and reduce HbA1c in people with type 1 diabetes who use it carefully under medical supervision. It is not a diet to attempt without a specialist diabetes team actively involved.
Low Carb Diet and Diabetes Management: A Practical Framework
For people with type 2 diabetes or prediabetes who have GP support, the practical framework for starting keto is straightforward:
Before you start
Get a baseline blood panel covering HbA1c, fasting glucose, full lipid panel, kidney function, and liver function. This gives you a clear baseline to measure progress against. Tell your GP or diabetes nurse you are planning to follow a ketogenic diet. Ask specifically about which medications carry a hypoglycaemia risk during the early weeks when blood glucose falls fastest.
During the first two weeks
Check your blood glucose daily, particularly before meals and two hours after meals, in the first two weeks. The keto diet can reduce post-meal glucose spikes within days, which means medication-induced hypoglycaemia can develop rapidly if doses are not adjusted. Track your readings and share them with your diabetes team at regular intervals. If you experience symptoms of hypoglycaemia, trembling, sweating, confusion, or weakness, treat immediately with glucose and contact your GP.
Foods to prioritise for blood sugar management on keto
The keto approach to diabetes management benefits from specific food emphasis beyond the standard keto framework:
| Food category | Best choices for diabetes management | Why it helps |
| Proteins | Fatty fish (salmon, mackerel, sardines), eggs, chicken thighs | Minimal blood glucose impact; omega-3s reduce inflammation |
| Fats | Olive oil, avocado, nuts, butter | Neutral blood glucose impact; monounsaturated fats support insulin sensitivity |
| Non-starchy vegetables | Leafy greens, broccoli, cauliflower, courgette, cucumber | Very low carb; fibre slows any glucose absorption |
| Dairy | Full-fat plain Greek yoghurt (measured), hard cheese, butter | Low carb; yoghurt provides protein with moderate lactose |
| Avoid entirely | Bread, pasta, rice, potatoes, sugar, fruit juice, most fruit | High carbohydrate load that directly raises blood glucose |
| Condiments to check | All sauces and dressings for hidden sugar | Hidden carbs are a common source of unexplained blood glucose rises |
For a complete guide to spotting hidden carbs that can undermine blood glucose management, see the guide on hidden carbs in food. For reference on the correct macros for your specific situation, the keto macro calculator provides a personalized starting point.
Frequently Asked Questions
Can diabetics do keto safely?
People with type 2 diabetes can follow a ketogenic diet safely with GP or diabetes team support, regular blood glucose monitoring, and proactive medication adjustment. The research strongly supports keto as an effective tool for type 2 diabetes management, with multiple studies showing significant HbA1c reductions and in some cases clinical remission. The critical safety requirement is medical supervision when starting, because keto’s blood glucose-lowering effect can interact with diabetes medications in ways that require dose adjustment. People with type 1 diabetes can also follow keto, but the complexity of insulin management in this context requires active specialist involvement rather than self-management.
How quickly does keto lower blood sugar in type 2 diabetes?
Blood glucose reductions can begin within the first 24 to 72 hours of starting a ketogenic diet, as the removal of dietary carbohydrate directly reduces the glucose load the body is processing. Post-meal glucose spikes reduce first. Fasting glucose typically begins to fall within the first week. HbA1c, which reflects average blood glucose over approximately three months, typically shows clinically significant improvement at the three-month mark. In people on insulin or sulphonylureas, the rapid early reduction in blood glucose means medication doses may need adjustment within the first week. This is why monitoring and medical communication in the first two weeks is the most important safety step.
Does keto cause hypoglycaemia in diabetics?
Keto itself does not cause hypoglycaemia. The hypoglycaemia risk in people with diabetes comes from diabetes medications, specifically insulin, sulphonylureas, and SGLT2 inhibitors, continuing at doses calibrated for a higher-carbohydrate diet while the diet itself is already lowering blood glucose. If medication doses are not reduced to match the improved blood glucose control that keto produces, blood glucose can fall too low. This is manageable with GP guidance and daily monitoring but requires active management rather than a set-and-forget approach to medication during the early weeks.
Is keto safe for people with type 2 diabetes who are on metformin?
Metformin does not cause hypoglycaemia when used as a single agent because it works by reducing liver glucose production rather than directly lowering blood glucose. People on metformin alone are generally at lower risk of hypoglycaemia when starting keto than people on insulin or sulphonylureas. However, metformin and other medications should still be reviewed by a GP when starting keto, because the improved metabolic control that keto produces may allow dose reductions over time. Additionally, some people experience digestive side effects from metformin that are temporarily more pronounced during the keto flu period in the first two weeks.
Can keto reverse type 2 diabetes permanently?
The research shows that keto can produce clinical remission of type 2 diabetes, meaning blood glucose returns to non-diabetic levels and medication may no longer be required. The 2025 systematic review cited above found remission rates of up to 62 percent at one year. However, remission declined to 13 percent by year five in the studies that followed participants that long, which is consistent with the finding that remission is maintained primarily by ongoing dietary adherence. People who maintain consistent low-carbohydrate eating tend to maintain their improved blood glucose control. People who return to a higher-carbohydrate diet tend to see blood glucose rise again. This does not mean keto failed. It means the dietary approach needs to be maintained to maintain the benefit, which is true of virtually all dietary interventions for chronic metabolic conditions.
Keto and Diabetes: The Evidence Is Strong, the Approach Requires Care
The keto diet and diabetes relationship is one of the most evidence-supported areas of nutritional science. For type 2 diabetes in particular, the research consistently shows significant improvements in blood glucose, HbA1c, and in a meaningful proportion of cases, clinical remission of the condition itself. These outcomes are achievable without the side effects that often accompany escalating pharmacological management.
The requirement for medical supervision is not a caveat that undermines these benefits. It is the practical gateway to accessing them safely. The blood glucose-lowering effect of keto is powerful precisely because it removes the carbohydrate load that drives blood glucose elevation, and that power needs to be matched with appropriate medication adjustment to prevent the hypoglycaemia risk that comes from medications doing double duty on a diet that is already doing the job.
For the full dietary framework that supports this outcome, the complete keto diet plan covers every component of a well-formulated ketogenic diet. For the specific metabolic mechanism behind keto’s effects on insulin and blood glucose, see the guide on keto diet and insulin resistance.
References
All external sources cited in this article are peer-reviewed studies or established medical references. This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making dietary changes if you have diabetes.
1. Zhou C, Wang M, Liang J, He G, Chen N. Ketogenic Diet Benefits to Weight Loss, Glycemic Control, and Lipid Profiles in Overweight Patients with Type 2 Diabetes Mellitus: A Meta-Analysis of Randomized Controlled Trials. PMC, International Journal of Environmental Research and Public Health, 2022
2. Das R, Mohammad N, Islam MS, et al. Long-Term Efficacy and Safety of a Low-Carbohydrate Diet in Type 2 Diabetes Remission: A Systematic Review. PMC, Cureus, 2025
3. Alluwyam AH, Estrella ED. Comparative Study Evaluating the Effectiveness Between Ketogenic and Low-Carbohydrate Diets on Glycemic and Weight Control in Patients With Type 2 Diabetes Mellitus: A Systematic Review and Meta-Analysis. PMC, 20224. Tinguely D, Gross J, Kosinski C. Efficacy of Ketogenic Diets on Type 2 Diabetes: a Systematic Review. PMC, Current Diabetes Reports, 2021