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16th May 2025
Mr Harrison is a 75-year-old man who comes to clinic for a review.
Mr Harrison is a 75-year-old man who comes to clinic for a review. He has recently begun to feel more nauseated and lethargic, and it is noted that there has been a slow increase in his lithium level over the past few months. He takes lithium for bipolar disorder and has done for the past 30 years. He has otherwise been well but states that he has been losing weight recently which is not intentional. On examination his blood pressure is 122/82 mmHg, pulse 70/min, and his BMI is 22 kg/M2. His laboratory results are as follows:
| Haemoglobin (Hb) | 13.5 g/dL | (13.5-17.5 g/dL) |
| White cell count (WCC) | 7.2 x109/L | (4-11×109/L) |
| Platelets (PLT) | 283×109/L | (150-400×109/L) |
| Sodium (Na+) | 137 mmol/L | (135-145 mmol/L) |
| Potassium K+ | 4.2 mmol/L | (3.5-5 mmol/L) |
| Creatinine (Cr) | 115 micromol/L (6 months ago was 100 micromol/L) | (50-10 micromol/L) |
What is the most likely cause of his increased lithium levels?
Select the SINGLE most appropriate option from the list below. Select ONE option only.
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