If you drink too much you can have water induced hyponatremia where the electrolyte levels in the blood are too low because your blood get diluted by drinking an extreme amount of fluid. However, that wouldn’t happen at the levels of fluid consumption you have reported here. If you’re having 2-2 ½ litres of fluids per day – provided you’re not exercising heavily or living in extremely hot weather conditions - it does not matter if some of those fluids are coming from tea or coffee, but ideally it wouldn’t all come from tea and coffee as they are both diuretics, meaning they make your bladder work overtime and you run to the loo more often and so you then need to drink even more water.    

If you’re trying to lose weight, make sure you count the Calories of the skim milk you’re adding to tea and hopefully you’re not adding sugar. It’s a good idea on a diet to stick to Calorie free dinks such as water. A good rule of thumb to tell if you’re having enough fluids is that your urine during the day should be a pale yellow, like the colour of straw. It is normal for it to be darker in the morning because your body has been reabsorbing fluids from your bladder during the night.

Dr Clare Collins