When you cut carbs on a ketogenic diet, your body starts flushing sodium at a much higher rate than normal. This isn’t a side effect of doing keto wrong; it’s a predictable shift in how your kidneys handle salt when insulin levels drop. Most people on keto need 3,000 to 5,000 mg of sodium per day, roughly double what a typical diet provides, just to keep up with what their body is now excreting.
How Low Insulin Changes Your Kidneys
Insulin doesn’t just regulate blood sugar. It also tells your kidneys to hold onto sodium. On a standard diet with regular carb intake, insulin stays elevated enough to keep sodium reabsorption humming along. When you drastically cut carbs, insulin drops, and your kidneys lose that signal. The result is a process called natriuresis: your kidneys begin dumping sodium into your urine, and water follows it out.
Research in the American Journal of Physiology demonstrated this clearly in animal models. When insulin was allowed to drop, sustained sodium and water loss followed. But when researchers kept insulin clamped at normal levels, the sodium flushing stopped entirely, even with the same metabolic changes happening elsewhere. The takeaway: it’s the drop in insulin itself, not anything else about the diet, that drives the salt loss. This is sometimes called the “natriuresis of nutritional ketosis,” and it begins within the first few days of restricting carbs.
Keto Flu Is Largely a Salt Problem
That collection of miserable symptoms people call “keto flu” maps almost perfectly onto what happens when your sodium drops too low. A study in Frontiers in Nutrition analyzed online reports of keto flu and found the most common complaints were headache (25%), fatigue (18%), nausea (16%), dizziness (15%), brain fog (11%), and feeling faint (8%). Some people also reported heart palpitations.
These are classic signs of low sodium and low blood volume. When sodium leaves, water follows, and your circulating blood volume shrinks. That means less blood reaching your brain when you stand up (dizziness, faintness), less efficient delivery of oxygen and nutrients (fatigue, brain fog), and compensatory changes in heart rate (palpitations). The same study found that the most frequently recommended remedy among experienced keto dieters was increasing sodium intake, cited 58 times, more than any other suggestion. Drinking broth, supplementing electrolytes, and adding potassium and magnesium rounded out the list.
Keto flu typically hits in the first week and can last anywhere from a few days to a couple of weeks. For many people, it’s entirely preventable with deliberate salt intake from day one.
The Aldosterone Cascade
Losing sodium triggers a hormonal chain reaction that makes things worse if you don’t replace it. When your body senses dropping sodium levels, your adrenal glands ramp up production of aldosterone, a hormone that tries to conserve sodium by pulling it back from your urine. The catch is that aldosterone works by swapping sodium for potassium: it saves one and dumps the other. So chronic sodium depletion on keto can drag your potassium and magnesium levels down as a secondary effect.
A 2023 study found that aldosterone levels increased by 88% in people following a ketogenic diet over six weeks, compared to no change in a low-fat diet group. That’s your body screaming for more sodium. If you simply increase your salt intake, aldosterone doesn’t need to spike as aggressively, and your potassium and magnesium stay more stable. This is why experienced keto dieters talk about all three electrolytes together. Sodium is the linchpin. Get that right, and the other two are much easier to maintain.
How Much Salt You Actually Need
Standard dietary guidelines suggest around 2,300 mg of sodium per day. On keto, you likely need 3,000 to 5,000 mg. That’s a significant jump, and it can feel counterintuitive if you’ve spent years hearing that salt is bad for you.
For context, one teaspoon of table salt contains about 2,300 mg of sodium. So you’re looking at roughly 1.5 to 2 teaspoons of salt per day from all sources combined, including what’s already in your food. Practical ways to get there include salting your meals generously, sipping bone broth (a cup can contain 500 to 1,000 mg of sodium), adding a pinch of salt to your water, or using electrolyte supplements designed for low-carb diets.
You don’t need to hit the target in one sitting. Spreading your intake throughout the day helps your body absorb and use it more effectively, and prevents the temporary water retention that comes from a large sodium load all at once.
What About Blood Pressure?
This is the question that makes people hesitate. Decades of public health messaging have linked salt to high blood pressure, so deliberately eating more of it feels risky. In the context of nutritional ketosis, the picture is different. Because your kidneys are actively dumping sodium, you’re replacing what’s being lost rather than piling excess on top of normal levels. Clinical data from Virta Health’s research program found that a modest increase in salt intake on a well-formulated ketogenic diet did not raise blood pressure.
A large multinational analysis published in the New England Journal of Medicine found the lowest overall mortality among people consuming 4 to 5 grams of sodium per day, which is above standard guidelines and right in the middle of the keto recommendation. That said, if you take blood pressure medication, the interaction between increased salt, ketosis, and your medication needs medical oversight. The diet itself often lowers blood pressure, which can make existing medication too strong.
Choosing the Right Salt
All salt delivers sodium, so the most important thing is simply getting enough. Beyond that, unrefined salts offer some minor advantages. Himalayan pink salt and unrefined sea salts contain trace amounts of minerals like potassium, magnesium, calcium, and iron that refined table salt lacks. The quantities are small, so don’t count on them as your primary source of those minerals, but they contribute to the overall picture.
A more strategic option is “lite salt,” which replaces roughly half the sodium chloride with potassium chloride. This lets you address both sodium and potassium needs with a single product. You can use it on food just like regular salt, though the taste is slightly different at high amounts. Some people also use dedicated electrolyte powders that combine sodium, potassium, and magnesium in ratios designed for ketosis.
Whatever you choose, plain iodized table salt works fine for the sodium piece. If your diet is already low in iodine (common if you don’t eat much seafood or dairy), iodized salt pulls double duty. The best salt for keto is the one you’ll actually use consistently.