Presence of a kidney stone in one kidney, by itself, even if it is large enough to obstruct the flow of urine, is not sufficient to cause impairment of kidney function as the second kidney compensates and the maintains the overall kidney function. So, the blood tests, which estimate the overall kidney function, can be normal even if one of the kidneys is not functioning optimally.A kidney stone on one side, if it is large enough to obstruct the urine flow, usually manifests with flank pain on that side, with or without nausea and vomiting. Smaller stones may manifest themselves with blood in the urine or with frequency or urgency (a frequent or urgent need to urinate). And, many patients with kidney stones have no symptoms.Keeping the above in mind and also the fact that your kidney function tests are normal, it is unlikely that the symptoms you are reporting (headache, nausea, loss of appetite and loss of interest in work since the last few months) are due to a kidney problem. A kidney stone can cause nausea but it is usually accompanied by other symptoms such as flank pain. Kidney failure can cause nausea, loss of appetite and shortness of breath, but your kidney function is normal.Depression may manifest with several of the symptoms that you mention, especially the loss of interest in your work. Studies have also shown that occurrence of nocturia (waking up at night from sleep to void) is 2-3 times more common in patients with depression. Moreover, some of the medications used to treat depression (including Tryptomer which can cause urinary retention) also affect the urination pattern. Other common causes of nocturia include drinking large volumes of fluids immediately prior to bedtime, intake of caffeine or alcohol prior to bedtime, night time diuretic (medicines that increase urine flow) therapy and diabetes mellitus (high blood sugar).As initial measures to alleviate your nocturia, I would recommend limiting your fluid, caffeine and alcohol intake prior to bedtime and emptying your bladder immediately prior to going to bed every night. Diabetes mellitus also needs to be ruled out.