diuretics and bodybuilding

Posted 1 month ago

Pharmaceutical diuretics

If you have been involved in bodybuilding for some years then you’ll be familiar with the concept of getting “dry”. This is part of the criteria required for the larger bodybuilding classes and is why some athletes use pharmaceutical diuretics. Although their use has increased in recent years, as with anything in bodybuilding, many people will implement them into their protocol without knowing how they work and/or with no awareness of their dangers. Moreover, taking pharmaceutical diuretics without a proper understanding of their function can also make an athlete look far worse on stage. Therefore, the aim of this article is to discuss how the most commonly used pharmaceutical diuretics in bodybuilding work. These are distinct from natural diuretics, which you can read more about here. Please note that the following article is for informational purposes only and should not be deemed as advice in any way.

What are they?

A diuretic is any substance that promotes diuresis: a process in which the kidneys filter fluid and salt out of the body, subsequently increasing urine production. In the medical world, diuretics are often used to help people with kidney/heart failure get rid of the fluid retention that comes with their condition. However, in the bodybuilding world, these are used for the cosmetic effect diuresis can have on the physique: removing excess water allows for a sharper look where muscle separation is more prominent, and the skin is tighter to the muscle.

Diuretics will have a direct impact on the body’s electrolyte balance because they influence the electrolytes that regulate fluid balance.

Electrolytes are particles that carry a positive or negative charge, and in nutrition, the term refers to the essential minerals found in your blood, sweat, and urine (e.g., sodium, potassium, chloride, calcium, magnesium, phosphate, and bicarbonate). These minerals are involved in many metabolic processes within the body including muscle function, maintaining acid-base balance, and relevant to diuretics, hydration.

Hydration or fluid balance is largely dictated by the delicate balance between sodium and potassium (Na+/Kpump) in cells. In the simplest way possible, our cells use sodium and potassium molecules to regulate how much fluid enters and exits them, to achieve homeostasis or balance. When our electrolytes are appropriately balanced (the right ratio of sodium to potassium, inside and outside the cell) water is regulated at the right levels inside and outside of each cell.

Diuretics work by influencing this “homeostasis regulator”: they impact different aspects of the fine-tuned balance between sodium and potassium, affecting the levels of these electrolytes in our body, and subsequently, the fluid balance inside and outside our cells. The main mechanism by which they do this is through the kidneys, which are the “motorway organs” for fluid balance in the body. Thus, most (but not all) diuretics used in bodybuilding work by blocking the reabsorption of sodium in specific parts of the kidneys: if the kidneys, as motorway organs, had “sodium exits”, diuretics act by blocking some of these. We will examine the most common diuretics and their specific mechanisms of action in turn.


Let’s start with the basics: in bodybuilding, you’ll hear people say that “where sodium goes, water flows”, and dyazide illustrates this well.

Dyazide is the one of most common diuretics used in bodybuilding and is referred to as a “potassium sparing” diuretic. But what does this mean? It works by blocking sodium and chloride reabsorption in a specific part of the kidneys: the renal distal convoluted tubule (via the Na+/Cl cotransporter, which accounts for 10% of sodium reabsorption in the kidneys). Why does this matter? Well, if this cotransporter is blocked, sodium reabsorption is blocked, and it is thus excreted out in our urine. As sodium leave the body, fluid does so with it, thus urine production is increased. In addition, given that fluid is regulated in the body via the sodium-potassium pump, the excretion of sodium via urine leads to a net increase in potassium levels within cells in the body. This is why dyazide is a potassium sparing diuretic (because it spares the potassium and excretes the sodium).


Aldactone is like Dyazide in terms of being ‘potassium sparing’ but its mechanism of action is distinct from the former. Whilst Dyazide works through blocking electrolyte absorption in the kidneys, Aldactone is an aldosterone antagonist. Again, what does this mean and why should we know this?

Aldosterone is a mineralocorticoid (hormone) produced by the adrenal glands that ultimately influences electrolyte and fluid balance within the body. In the kidneys, it increases sodium channels, allowing more sodium to be reabsorbed by the body, leading to an increased excretion of sodium from the body. This results in increased blood pressure and fluid retention.

The word antagonist effectively means blocking. Therefore, Aldactone blocks the receptors in the distal convoluted tubule (same as Dyazide) at which aldosterone usually binds to, meaning that sodium cannot be reabsorbed and will be excreted in the urine. Remember, where sodium goes, water flows, thus we see an increase in urination and fluid leaving the body.

Loop diuretics

Loop diuretics such as furosemide (Lasix), in my opinion, have no place in bodybuilding. These act upon the sodium-potassium-chloride transporter (Na+/K+/Cl cotransporter) in a place in the kidneys called the thick ascending limb of the loop of Henle. In short, it means that loop diuretics block reabsorption of these electrolytes, resulting in fluid loss from the body. This part of the kidney is involved in a greater reabsorption rate of sodium (25%) compared to the other mentioned sites, and therefore its effects on “drying out” can be more drastic. However, the blocking of this cotransporter leads to an increased loss of calcium in the urine – given that calcium plays a key role in the contraction and metabolism of the heart, excessive loss of this mineral and persistent low levels of it can lead to heart failure.

The rebound

It’s worth pointing out that if you have used a drug that has manipulated your electrolytes and fluid balance, your body will always try and get back to homeostasis (normal) once the drug usage has ceased. As you’ve been pushing sodium and fluid out of the body, it will try to do the opposite. It does this by increasing hormones such as aldosterone, which we have already learned increases sodium channels and Antidiuretic hormone (ADH). This is the hormone that is involved in regulating the amount of water in your body, by controlling the amount of water kidneys reabsorb as they filter out waste from your blood. An increased production of ADH leads to more concentrated urine to reduce the loss of fluid from the urination, thus making our body retain fluid.

Both these hormones will be increased in response to low sodium/fluid levels. Once you’ve ceased usage of diuretics these hormones will remain elevated for some time, which will lead to significant water retention and be reflected as a large increase on the scales. However, these hormones do tend to come back to balance after three to four days or so, which results in the loss of the fluid that was being held, and as such, a weight drop.

The dangers

Like anything in assisted bodybuilding, the use of these drugs can come with a price. How you react to one substance might be completely different to another, and the same goes for the reaction to these between individuals. Just because ‘Big Davy’ down in the gym said that he was fine when he used one of the above, it doesn’t mean you will be.

If you understand the physiology, and the needs of an individual who is considering using them, then these can help achieve a great dry look on stage. However, if they are used incorrectly, in combination, or in excess, they can result in death. Unfortunately, we have seen this time and time again in the industry, and more recently in the past couple of years, and it’s so sad to see. Therefore, if you aren’t sure how to use them, please don’t. If you’re going to, then seek the advice of a medical professional and an experienced coach please.

In conclusion, the use of pharmaceutical diuretics in bodybuilding is becoming more and more prevalent. The majority of these diuretics will act by blocking sodium reabsorption, and thus fluid, back into the body. This will lead to a dryer look but can have some real consequences on the body if used incorrectly. After their use, you will see a large rebound which can take a few days to dissipate. In recent years we have seen people die from abusing these drugs, so caution is advised.

Vaughan Wilson Bsc Hons