Could be from the diet. Some folks get dehydrated and that can definitely cause leg cramps. But it sounds like you're drinking plenty of water. Are you getting enough salt? Try drinking a cup of salty broth before bedtime and see if that helps.

Another possibility is that you could be deficient in Vitamin D. Years before I went low-carb, I went thru a period when I got HORRID leg cramps every single night. And I'm not talking about garden-variety leap-out-of-bed and stretch out the calf-muscle charlie-horse cramps either. THOSE hardly make me grimace. I'm talking about my inner-thigh muscles cramping so hard it felt like my bones were going to break under the stress. The knots were so tight my inner thighs would have "hollow" spots the size of a softball and when my husband tried to massage the cramps out, he said that the muscles felt like they were made of iron. There as no way I could "stretch" the cramp out and it would go on and on for what seemed like hours. By the time the cramp would release, I'd be covered with sweat and my throat would be raw from screaming.

The cramps went on every night for months until I used to dread going to bed at night and was totally sleep-deprived. My doctor at the time just shrugged and said "some people get leg cramps at night.... they won't kill you." Well, I reached the point where I WISHED that they would kill me.

Then I read somewhere that vitamin D might help so I bought a bottle of the oil capsule kind and took about 20 capsules all at once. Seriously, I was that desperate! The leg cramps went away like magic. I woke up the next morning and realized that I had slept thru the night without waking with leg cramps a single time! Since then I've kept myself on a 2000 mcg/day vitamin D regimen and never get leg cramps anymore...except when I run out of vitamin D and go for a few days without taking any. The low carb diet doesn't seem to have an effect one way or the other for me. BTW, when I saw my doctor a couple of months after bingeing on Vitamin D that one time and then continuing to take 2000 mcg a day, and told him that Vitamin D had made cramps go away, he was concerned that I could be overdosing on vitamin D and ran a blood test. Turned out that after two months of taking very high daily doses, I was still at the extreme LOW end of the scale on D. Apparently I must have been literally devoid of Vitamin D previously. Turns out my body simply doesn't store it normally.

I've also heard that some people get night-time leg cramps if they're deficient in magnesium so you might try a little magnesium citrate. (You'll find 1 pt jars of magnesium citrate in your pharmacy with the laxatives. A bottle costs about $2 most places.) Be careful with that stuff tho because it does have a strong laxative effect. If your leg cramps are due to magnesium deficiency, a tablespoon full of mag citrate daily mixed into your lemon water might be all you need.

Good luck. Doctors do tend to ignore us when we complain about leg cramps but if they only knew! Severe leg cramps can have a major debilitating effect on one's life. And you should NOT have to suffer them.

I wish you all the best in finding out what is causing yours and in finding a cure a whole lot quicker than I did!