You cut the carbs, the scale moved fast, and then day three arrived with a headache, dead legs, and a fog you can't blink away. That's the "keto flu," and most people blame the lack of carbs itself. The real culprit is usually simpler and more fixable: your kidneys are dumping sodium, and you haven't replaced it. Getting electrolytes on keto right is the difference between a miserable first week and a smooth transition.
Why low-carb makes you lose sodium
When you stop eating carbohydrate, insulin falls. That's the whole point of the diet, and it's also why you feel rough. Insulin doesn't just manage blood sugar; it quietly tells your kidneys to hold on to sodium. When insulin drops, that signal goes quiet and the kidneys start excreting more sodium in your urine, taking water with it. This antinatriuretic role of insulin is well documented in the renal physiology literature (see DeFronzo's classic review, The effect of insulin on renal sodium metabolism).
So in the first days of low-carb eating you lose water weight quickly, but you're also flushing the electrolyte that governs how much fluid your body can hold. Low sodium is what produces the classic keto-flu cluster: headache, fatigue, lightheadedness on standing, and muscle twitchiness. It isn't the absence of bread making you feel bad. It's the absence of salt.
The part nobody tells you: it's temporary
Here's the non-obvious piece. The heavy electrolyte loss is a feature of the transition, not a permanent tax on low-carb living. Once your body adapts to running on fat and your glycogen stores stop draining, the exaggerated water-and-sodium flush settles down. Your sodium needs on keto stay somewhat higher than on a standard diet, but the dramatic losses of week one don't last. If you get through the adaptation window well-salted, most of the "flu" never shows up.
How to cover your sodium during adaptation
During that first week of heavy losses, low-carb sodium needs can climb toward a few grams a day — more than any daily hydration stick is designed to carry on its own. The clean way to hit a keto sodium target is to anchor your day with a good hydration drink and then salt your food generously: broth, salted whole foods, and a pinch of extra salt in your water when the day calls for it. Think of your electrolyte stick as the reliable daily base — the thing that makes your water count and covers the minerals that are hard to get — and real food as where the big adaptation-phase sodium comes from.
Where burbo fits on a low-carb plate
burbo is built for exactly this daily-anchor role, and it brings two things keto dieters specifically need. First, it's an excellent source of magnesium (100 mg as magnesium bisglycinate, 24% of the Daily Value), and magnesium supports normal neuromuscular function — directly relevant when low-carb transitions bring on muscle twitches and restless legs. Bisglycinate is a well-absorbed, gut-friendly form, so it's a genuine, measurable claim. Second, burbo is calorie free, so it won't nudge you out of ketosis: it's sweetened with OnoSweet, a zero-calorie form of Reb M, plus a trace of organic agave for flavor — no meaningful sugar or calorie load to worry about.
On the hydration itself, each stick delivers 327 mg of sodium, and sodium supports fluid absorption and retention — the same sodium-coupled transport behind oral rehydration is what helps you hold on to the water you drink instead of sending it straight through. That makes burbo a strong daily base through the transition; on the heaviest adaptation days, pair it with the extra sodium from food and broth. (For quality, burbo is also third-party tested for heavy metals — a heavy-metals screen specifically.)
A simple plan for the first week
Anchor your hydration, then salt your food. A reasonable rhythm: one stick in a full bottle of water in the morning, another around a workout or the hottest part of the day, and — if you're a heavy or salty sweater feeling wiped out — a third, always in its own full bottle. Alongside that, lean on broth and salted meals to carry the bigger adaptation-week sodium load. Two sticks a day is comfortably fine and three is the practical ceiling — each stick also carries a full day's folate and B vitamins set against adult Daily Values, so beyond three, keep the fluid high and take additional sodium from food or plain salt rather than more sticks. More sticks should always mean more fluid, never a stronger, saltier drink.
One caution: if your low-carb week goes sideways into actual illness with vomiting or diarrhea, that's a job for an oral rehydration solution, not a hydration stick. burbo is for everyday and training hydration, not medical rehydration.
The takeaway: keto flu is mostly a salt-and-magnesium story wearing a scary name. Anchor each day with hydration and well-absorbed magnesium, salt your food generously through the adaptation window, keep the fluid high, and the "flu" mostly never arrives — with the heaviest sodium coming from your plate, not from stacking sticks.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. How this article was researched and written: our editorial standards.