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Dr. D. Love
Dr. D. Love, Doctor
Category: Medical
Satisfied Customers: 19453
Experience:  Family Physician for 10 years; Hospital Medical Director for 10 years.
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In September I had an op for a hernia and had mesh inserted

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In September I had an op for a hernia and had mesh inserted across my abdomen
since then I have lost over a stone in weight and I had a severe water infection on holiday.
blood tests, chest xray show no abnormalities and I am waiting for scans. I realise that
I pass a lot more fluid that I take in, I have no pains or urgent rushes to the toilet but during the night having only a coffee since 3-4pm I empty my bladder fully minimum 3-4 times, could this be a reason for weight loss.
Hello from JustAnswer.

There are several issues to consider with this question.

The simple, direct, answer to your question is yes, an excessive amount of urination will cause a loss of weight. Water is a very large component of the human body, and any condition that causes a person to lose more water than is being placed into the body, so that there is a net loss of water, will cause a loss of weight.

It is also true that there is a direct correlation to the volume of lost water. One litre of water weighs 1 kg (by definition), so that if there is a loss of 3 litres of water compared to an intake of 2 litres of water, with a net loss of 1 litre of water, it will directly cause a loss of weight of 1 kg.

It is important to note that there are some sources of intake and loss of water that is not readily measurable, called insensible water gain or loss. Foods contains water, assuming that you are not eating dehydrated foods without reconstitution. There is some water loss in sweat and in water vapour in expired breaths. As a general rule, there is about the same amount of insensible water gain and loss, so that the amount of water in fluids that someone drinks is equal to the amount of urine that is passed, but there can be certain conditions in which a person may get more or less insensible fluid intake or loss. We see this more often as a cause of increased insensible fluid loss, so may explain a decrease in urine output. A common example would be a fever, that increases insensible fluid loss in sweat and water vapour, so can contribute to dehydration if the person does not drink extra fluid while sick.

In someone with no change in insensible fluid intake, an increase in urine volume compared to fluid intake can cause weight loss, and the magnitude of the weight loss would be directly related to the magnitude of the excess volume of urine, which will be additive over time.

An excessive amount of fluid loss in the urine usually occurs because of systemic illnesses that cause an increase in urine volume, such as diabetes mellitus or diabetes insipidus, or diseases that affect the function of the kidney. It may require an consultation with a Nephrologist (a kidney specialist).

So, yes, excessive urination compared to fluid intake can cause fluid loss, particularly if there has been no change in insensible fluid intake, and it would be appropriate to assess for systemic or kidney illnesses.

If I can provide any further information, please let me know.

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