A low-carb diet can be one of the most effective dietary strategies for managing diabetes, particularly type 2 diabetes. In clinical studies, people with type 2 diabetes who followed a low-carb, high-fat diet reduced their A1C by an average of 1.29 percentage points more than those receiving usual care, a significant improvement that can shift someone from poorly controlled diabetes into a much healthier range. The approach works because carbohydrates are the nutrient most directly responsible for raising blood sugar, so eating fewer of them means your body has less glucose to manage in the first place.
What Counts as Low Carb
There’s no single definition, and that’s part of what makes the conversation confusing. A ketogenic diet, the strictest version, typically limits carbohydrates to under 50 grams per day (less than what’s in a single plain bagel) and sometimes as low as 20 grams. At that level, roughly 70 to 80 percent of your daily calories come from fat, with only 5 to 10 percent from carbs.
Most people searching for “low carb” aren’t necessarily aiming for a full ketogenic diet. A moderate low-carb approach might mean 50 to 130 grams of carbohydrates per day, compared to the 200 to 300 grams many people eat on a standard diet. Even this moderate reduction can produce meaningful improvements in blood sugar control. The benefits tend to scale with the degree of restriction, but any reduction from a high-carb baseline helps.
Blood Sugar Improvements in Type 2 Diabetes
The evidence for type 2 diabetes is strong. In a community-based study published in BMJ Open Diabetes Research & Care, people following a low-carb, high-fat diet achieved an average A1C of 6.67% by the end of follow-up, compared to 7.8% in the usual care group. They also lost an average of 12.8 kilograms (about 28 pounds) more than the comparison group. That weight loss matters because excess body fat, especially around the midsection, worsens insulin resistance.
These results aren’t unusual. Across multiple trials, low-carb diets consistently outperform standard dietary advice for A1C reduction in people with type 2 diabetes. The mechanism is straightforward: fewer carbohydrates entering your digestive system means less glucose entering your bloodstream, which means your pancreas doesn’t need to produce as much insulin and your cells aren’t overwhelmed trying to absorb it.
Effects on Cholesterol and Heart Health
Since people with diabetes already face higher cardiovascular risk, the effect of any diet on cholesterol matters. A meta-analysis of randomized controlled trials in people with type 2 diabetes found that low-carb diets reduced triglycerides by about 20 mg/dL on average and raised HDL (“good”) cholesterol. Both of these changes are favorable for heart health. Importantly, LDL (“bad”) cholesterol and total cholesterol were not significantly affected.
This is a common concern people raise about low-carb diets, since they often involve eating more fat. The data suggests the shift toward healthier triglyceride and HDL levels offsets worries about fat intake, at least in overweight and obese people with type 2 diabetes. If you have a personal or family history of high LDL cholesterol, monitoring your lipid panel after starting a low-carb diet is still a reasonable idea.
Low Carb With Type 1 Diabetes
Type 1 diabetes is a different situation. Your body produces little or no insulin, so you rely on injected insulin to manage blood sugar. A low-carb diet doesn’t replace that need, but it can make blood sugar significantly easier to control. In a clinical trial published in PLOS ONE, adults with type 1 diabetes who followed a low-carb diet increased their time in the target blood sugar range from 59% to 74%, a jump of about 15 percentage points. They also reduced their total daily insulin from 65 units to 49 units per day.
Blood sugar swings also shrank considerably. The large spikes and drops that make type 1 diabetes exhausting to manage became smaller and less frequent during the low-carb intervention. This matters for daily quality of life, since fewer swings mean fewer episodes of feeling shaky, foggy, or unwell. The tradeoff is that eating very low carb with type 1 diabetes requires careful insulin adjustment and close monitoring, especially early on.
Hypoglycemia Risk When Starting
One of the most important practical concerns is low blood sugar. If you take insulin or a class of oral medications called sulfonylureas (common brand names include Glucotrol, Amaryl, and Glynase), cutting carbs without adjusting your medication dose can cause dangerous drops in blood sugar. These medications are dosed based on your usual eating pattern. When you suddenly eat far fewer carbs, the same dose of medication can push your blood sugar too low.
This doesn’t mean you can’t go low carb on these medications. It means you need to work with your prescriber to reduce doses proactively, often before you start or within the first few days. Some people with type 2 diabetes who achieve strong blood sugar control on a low-carb diet are eventually able to reduce or stop certain medications entirely, though this should always be done with medical guidance rather than on your own.
A Serious Risk for Some Medications
There’s a less common but more dangerous risk that applies to people taking a newer class of diabetes drugs called SGLT2 inhibitors (names ending in “-flozin”). These medications work by causing your kidneys to excrete excess glucose through urine. When combined with very low carb intake, they can trigger a condition called euglycemic ketoacidosis, where dangerous acid levels build up in your blood even though your blood sugar reads normal.
The “normal blood sugar” part is what makes this condition deceptive. You might feel nauseated, fatigued, or short of breath, check your glucose monitor, see a normal number, and assume you’re fine. Symptoms to watch for include nausea, vomiting, abdominal pain, and unusual fatigue. If you take an SGLT2 inhibitor and want to try a low-carb diet, this is a conversation to have with your doctor before making changes, not after. In some cases, the SGLT2 inhibitor may need to be paused or switched to a different medication.
What the Guidelines Say
The American Diabetes Association’s 2024 Standards of Care don’t single out any one diet as the best for diabetes. Their updated nutrition guidance emphasizes “food-based eating styles” that include healthy fats, with particular mention of Mediterranean-style eating patterns. Low-carb diets fit within this framework, especially when the fats come from sources like olive oil, nuts, avocados, and fatty fish rather than processed meats and fried foods.
In practice, most diabetes specialists recognize low-carb eating as a legitimate tool for blood sugar management. The shift over the past decade has been away from recommending a single diet and toward supporting whatever sustainable eating pattern helps a given person achieve better glucose control, a healthier weight, and improved cardiovascular markers.
Making It Sustainable
The biggest challenge with any dietary approach is sticking with it long term. Many studies show strong results in the first 6 to 12 months of a low-carb diet, with some people gradually drifting back toward higher carb intake over time. The blood sugar benefits only last as long as the dietary changes do.
A few practical strategies help. First, you don’t have to go extremely low carb to see results. Even reducing from 250 grams of carbs per day to 100 or 130 grams can improve blood sugar meaningfully. Second, focusing on which carbs you eliminate matters. Refined grains, sugary drinks, and processed snacks have the largest impact on blood sugar and are the easiest to cut without feeling deprived. Vegetables, legumes, and small portions of whole grains have a gentler effect and add fiber and nutrients. Third, building meals around protein, healthy fats, and non-starchy vegetables tends to keep you full longer, which makes the transition easier than simply removing carbs and leaving a gap on your plate.
For most people with diabetes, reducing carbohydrate intake is one of the most direct and effective ways to improve blood sugar control. The degree of restriction that works best varies from person to person, and the right approach depends on your medications, your type of diabetes, and what you can realistically maintain over months and years rather than weeks.