Other people report the same thing occasionally on forums. The standard medical textbook on clinical use of ketogenic diets doesn't mention it, which suggests that it's not very common. There doesn't seem to be a single mention of this in the biomedical literature, which also suggests that it's not very common. But it does happen. You're not the only one.

It's possible that you were close to the threshhold for night sweats for other reasons before you began your ketogenic diet and ketosis nudged you over.

If you are taking any medications, you might want to consider the possibility that they are interacting with ketones in your blood.

Two things occur to me which might help and can't hurt. First, make sure you're getting adequate amounts of all micronutrients. You can help make this happen by including certain foods (like liver) in your diet but the only practical way to accomplish it completely is with supplements. Perfect Health Diet by Paul and Shou-Ching Jaminet contains excellent advice about micronutrients.

Second, whenever you experience unpleasant symptoms from ketosis, you can reduce or eliminate symptoms within a few minutes by eating a tiny amount of sugar. This is what people on medical ketogenic diets do. It's a way of fine tuning the degree of ketosis.

Children on medical ketogenic diets are usually told to drink 30 ml of orange juice for this purpose. That's about 2.5 grams of sugar. I eat a stalk of celery instead. Believe it or not, the tiny amount of sugar in a stalk of celery (about 1.5 g) is enough to affect me noticeably within about 20 minutes. If it doesn't work, I eat another stalk.

I'm on a medical ketogenic diet so my blood ketone levels are probably higher than yours and I may be more sensitive to sugar than you. Therefore you may need more sugar to notice an effect.

References:

Jaminet, Paul and Shou-Ching. Perfect Health Diet. 2010. YinYang Press: Cambridge.

Strafstrom, Carl E. and Jong M. Rho. Epilepsy and the Ketogenic Diet. 2004. Humana Press.

A quick Google search is bringing up results for me--apparently this is a symptom for some people in ketosis, though not necessarily all. I'm pretty sure we shed ketones through the sweat as well as through breath and urine.

Make sure to stay hydrated and give it a little time, could be the symptoms will improve after a week or so.

HYDRATE, HYDRATE AND HYDRATE MORE>>>>>> please.... you tend to forget you need water!

I haven't had night sweats when in ketosis. But assuming you're drinking more water, supplement magnesium and potassium to counteract the losses from drinking so much water.

I've been on the Ideal Protein diet, which is ketogenic, for 4 weeks. The diet includes several different kinds of vitamins and supplements, two of which have magnesium. In addition to IP diet, I've had low vitamin D for several years since having Lyme's disease. Although the low Vitamin D has improved greatly, I still take 50,000 IUs per week. When I forget to take it, I begin feeling run down which reminds me and usually a day or two after taking the vitamin D, I feel very happy and energetic. Just this week I had severe night sweats and felt run down so, I took the Vitamin D. Not sure if the low vitamin D had any correlation with the night sweats. I'm also menopausal so, it could be hormonal too.

If your symptoms are worrisome, maybe you should discontinue the ketogenic diet. The one thing I can say is that I'm feeling happier. Maybe because I've lost weight, maybe because I'm not in a carbohydrate fog. Whatever it is, ketosis reduces my food cravings. When I'm eating carbohydrates my food desires are beyond my control. Wondering how I can manage to avoid that awful carbohydrate high for the rest of my life without being in ketosis. I only want to stay in ketosis for 6 months then transition back to a balanced diet. I realize now that the balance needs to involve a lot less carbs than I was eating before.