If you’re experiencing leg cramps on keto, I sympathize. Cramping is NOT pleasant—and those suckers can definitely cut into your quality of life.
It was common for my former coaches’ community members to start cramping after cutting carbs. Muscle cramps are a common complaint of keto flu—a laundry list of symptoms that include not only cramps, but headaches, low energy, fatigue, insomnia, GI issues, and worse. These symptoms usually crop up in the early stages of low-carb dieting.
Muscle cramps can be extremely uncomfortable. In the throes of a calf cramp, people question why the hell they’re even doing this keto thing. They’re kind-of like weekend warriors who overtrain and then question the point of exercise. Both people want to burn fat, lose weight, and feel better, but no health benefit is worth that kind of agony.
I get it. A health regimen should make you feel better, not worse.
Luckily, leg cramps aren’t required for an effective keto diet. They often stem from inadequate hydration—specifically, inadequate electrolytes.
This means that most cases of keto leg cramps are preventable. I’ll share how to fix them at the end of this article.
It doesn’t mean, however, that all muscle cramps are resolved in the same way. Not all cramps can be blamed on low-carb dieting. So let’s first cover the basics of muscle cramps, then we’ll talk about cramps on keto.
Muscle Cramps 101
A muscle cramp is defined as an uncomfortable, involuntary muscle contraction. These contractions (also called spasms) can occur anywhere, but most commonly affect the calves, quadriceps, feet, hands, and abdominals. According to one source, about 80% of muscle cramps occur in the calf.
Leg cramps are mysterious things. They’re nearly impossible to predict. They seem to come from nowhere. They can stick around for seconds, minutes, or hours. And neither stretching nor massage typically helps.
Muscle cramps don’t just impact the local muscle… They can affect the entire body. They can even trigger a raft of emotions.
What increases one’s risk for leg cramps? The keto diet, for one. We’ll talk about why in a minute.
Other risk factors include age, BMI, cardiovascular disease, kidney disease, cancer, allergies, long or intense exercise, exercising in the heat, and the use of many medications.
Let’s talk about leg cramps during exercise now. Understanding this phenomenon will help explain why keto dieters get more leg cramps.
Leg Cramps from Exercise
Two main theories explain why cramps occur during exercise:
- The muscle fatigue theory
- The hydration theory
Support for the muscle fatigue theory is found in endurance sports. One study, for instance, found that marathon runners reported all their cramps during the second half of the race as fatigue was setting in.
But endurance athletes also cramp up in cool climates, when sweat loss isn’t a major factor. So hydration can’t explain everything.
Why might muscle fatigue cause cramping? Researchers aren’t exactly sure, but the simplified hypothesis is that muscle overuse alters the communication between the brain and the muscles, leading to nervous system activation and cramping. It’s not clear, however, why only a small percentage of athletes cramp up during grueling efforts.
The other theory is that muscle cramps result from suboptimal hydration. Football players, for instance, are more likely to cramp when training in the heat, likely due to heavy sweat loss.
Does this mean that more water is the antidote for leg cramps? Not so fast.
In one study, even severe dehydration (net water loss of 5% of body weight) didn’t increase cramping. But healthy hydration isn’t just about preventing dehydration. It’s about maintaining electrolyte levels too.
Electrolytes and Leg Cramps on Keto
Electrolytes are minerals with many crucial functions in your body. They conduct electricity throughout your nervous system, maintain fluid balance, and help muscles contract and relax.
Electrolyte deficiencies are undeniably linked to leg cramps. The main cramp-causing deficiencies are:
- Sodium deficiency
- Potassium deficiency
- Magnesium deficiency
- Calcium deficiency
When it comes to cramps on keto, the first three deficiencies are the most common. Let’s take them one at a time.
Sodium Deficiency
Sweating increases your risk of developing muscle cramps. That’s because you lose sodium through sweat, increasing the risk of sodium deficiency.
Back in the 1920s, sweaty industrial workers were cramping up frequently. What solved the problem? Yes, salt supplementation.
Again, sodium deficiency equals cramps. Football players who sweat more, cramp more. The same holds for dialysis patients who aren’t given enough sodium.
But sweating isn’t the only risk factor for low sodium. The keto diet is too.
Keto dieters tend to be sodium deficient because:
- They tend to consume fewer high-sodium foods
- They excrete more sodium through urine
You read number two correctly. Restricting carbs decreases the amount of insulin in circulation, and low insulin levels decrease sodium retention. It’s actually a part of a really complex chain affecting the HPTA Axis, but this explanation will work for our discussion’s sake. End result: you lose more sodium on keto.
With less sodium coming in and more going out, should we be surprised that low-carbers are deficient in sodium? Should we be surprised they’re cramping?
Potassium Deficiency
Most people know that potassium helps with muscle cramps. Like sodium, potassium is a key nutrient for muscle function.
Although hypokalemia (low serum potassium) is a well-documented risk factor for leg cramps, more research is needed to prove that potassium supplements can prevent cramping. I believe that they can, but I’d like to see an RCT on this topic.
Yet even without perfect data from the lab, there’s no downside to hitting 3.5–5 grams of potassium per day. Only about 3% of Americans hit the IOM target of 4.7 g/day, likely contributing to our collective blood pressure problem. And we DO have solid clinical data that potassium supplementation lowers blood pressure in those with hypertension.
If you’re on a ketogenic diet, you may not be hitting that target either. Many good sources of potassium—potatoes, fruits, carrots, etc.—contain too many carbs to keep you in ketosis.
And as with sodium, a low-carb diet increases potassium loss through urine. There we go again. Less potassium in, more out.
Magnesium Deficiency
About 30% of the population is subclinically deficient in magnesium. Since magnesium is critical for muscle contraction and relaxation, this could be driving many cases of leg cramps.
If you’re not mainlining green leafy vegetables on keto, you’re probably not getting enough magnesium. Magnesium sits at the center of the chlorophyll molecule. If it’s green, it’s probably rich in magnesium.
But getting enough magnesium from diet alone isn’t easy. (A total of 400–600 mg per day is a good evidence-based target for adults.) There’s a case for supplementation here.
Blood Panel Information
By now you might be wondering if you should test for electrolyte deficiencies in the blood. Can’t you just assess sodium, potassium, magnesium, and calcium status in the serum?
Actually, bloodwork isn’t a reliable way to detect dietary electrolyte deficiencies. Why? Because your body pulls these minerals from other sources (like bone) if they drop in the serum. Out of the bone, into the blood.
When sodium or potassium levels are in range on an electrolyte panel, that just means your kidneys are working to balance fluid and electrolyte levels. It doesn’t say your dietary intake of electrolytes is optimal. Something to keep in mind.
How to Prevent Leg Cramps On Keto
Leg cramps are not inevitable on keto. Heed the following tips to prevent them.
#1: Allow recovery time
Although the data is difficult to parse, it appears muscle fatigue increases the likelihood of leg cramps. The more tired your muscles become during exercise, the more likely you are to cramp up.
If you often cramp while exercising, consider ramping down the duration or intensity of your training. I’m not saying you should stop entirely. Just ease off and see if the cramps diminish.
You might also allow a day or two of rest between harder or longer efforts. Unless you’re training for a competition, limiting your training volume makes a lot of sense for preventing leg cramps.
It might also be prudent to rest more if you are training for a big event. Listen to your body.
#2: Drink to thirst
Most hydration websites blame dehydration for leg cramps. For starters, this is false. Even serious dehydration doesn’t increase cramp frequency in athletes.
Blaming dehydration for cramps is also dangerous. Why? Because people get scared of dehydration and overcompensate. They drink too much water.
But when we drink too much sodium-free water, it dilutes blood sodium levels. Low blood sodium levels (called hyponatremia) affects a large proportion of endurance athletes.
Low sodium is also a problem for keto acolytes. The stock advice is to drink more water, but that just dilutes serum electrolytes and makes things even worse.
To avoid dehydration AND overhydration, simply drink to thirst. Your body excels at telling you when you need more fluids.
#3: Take electrolytes
The most important tip for preventing leg cramps on keto? Dial in your electrolytes.
This means consuming enough of each essential electrolyte through diet and supplementation. How much is enough? Based on the scientific literature, I recommend baseline daily intakes of:
You can get most of the way there through diet. On a keto diet, this means eating lots of green leafies for potassium and magnesium, and cruciferous veggies, bones, and dairy (if tolerated) for calcium. The sodium will come from salting your food. (4–6 grams sodium is about 2–3 teaspoons of salt.)
You can also salt your water. To make your electrolyte water palatable, add a squeeze of lemon or use a no-sugar electrolyte drink mix like Drink LMNT. With LMNT, you’ll also get some extra potassium and magnesium for cramp prevention.
Before we sign off, if you remember one thing about preventing leg cramps, remember to get enough electrolytes. Your muscles will thank you.
