One of the many incomplete tasks in the hydration space is using biomarkers to objectively identify dehydration. For the most part, dehydration is a clinical diagnosis, from signs and symptoms that signify loss of water and electrolytes from the body.
However, when you consider this objectively to define how much a person is dehydrated, some laboratory biomarkers can help. One of such biomarker sets is that of the BUN: Creatinine ratio.
Normally, when we eat protein, the peptide bond gets broken to yield amino acids. These are then absorbed through the gut and are the building blocks for protein. As the peptide bond breakage creates nitrogenous waste products, ammonia is produced which is converted into a nontoxic waste called urea by the liver.
The measurement of urea in the blood is done via Blood urea nitrogen test or simply referred to as BUN.
Creatinine, on the other hand, is a molecular protein produced by the muscle and is relatively freely filtered by the kidneys. Hence, it is commonly used as a kidney function test as most adults make the same amount of creatinine every day. There are relatively few things that can affect the creatinine level hence the majority of fluctuations can be attributed to a change in kidney function.
Together, both BUN and creatinine are used to estimate the kidney function. But since kidney function is determined to some extent by a person’s fluid intake, a dehydrated body can lead to a high BUN: creatinine ratio. This is also called pre-renal azotemia.
Amongst a few others, one major factor is dehydration. When the body is in a negative state of fluid balance, the kidney function gets affected. A high BUN: Creatinine ratio in this case indicates dehydration but the good news is that it is reversible. Drinking enough fluids can improve the high BUN: Creatinine ratio.
A high BUN/Creatinine ratio can also be due to an ongoing kidney problem. In this regard, both BUN and creatinine are elevated modestly or proportionately, and the ratio hence is not necessarily higher than 20.
Let’s take an example of dehydration below---
A 70 kg individual who is 40 years old just ran 2 miles in the hot sun, and did not have anything to drink. Not even a glass of water. If we sampled his laboratories, his chemistry profile may look something like: BUN level of 28 mg/dl and creatinine of 1.1 mg/dl. Notice, that the BUN/Creatinine ratio in this case is higher than 20 indicating dehydration.
Now if the same person had about 1 liter of water to drink during that run, the laboratories would look something like this: BUN of 16 mg/dl and creatinine of 0.95 mg/dl. Notice, in this case, the BUN/Creatinine ratio is not higher than 20 and BUN and creatinine have normalized.
So, to summarize, the high BUN-Creatinine ratio, particularly if it is more than 20 and the person has a normal creatinine, usually indicates dehydration. However, if BUN and creatinine are both elevated significantly and the ratio is < 20, it may indicate an underlying kidney problem.
Now let’s take an example of kidney problem that can elevate the BUN and Creatinine levels---
A 58 year old male who weighs about 70 kg has high BP and early diabetes. His laboratories show a BUN level of 29 mg/dl and a creatinine level of 1.6 mg/dl. He is adequately hydrated. In this regard, the BUN-Creatinine ratio is not higher than 20 and his BUN and creatinine levels are elevated in a “well-hydrated” state. This indicates he has an underlying kidney problem.
Patients with chronic kidney disease from many causes (common being high BP, diabetes, etc.) are usually diagnosed with a BUN and creatinine test along with urine studies. Sometimes, imaging using an ultrasound or CT scans may be needed and are best directed by medical professionals.
This is not usually uncommon in practice but a low BUN can be caused by very low protein intake as seen in cachexia or liver cirrhosis. Some cases of malnutrition will also have very low BUN: Creatinine ratio.
Individuals who have bulimia (eating disorder) or those who are trying some extreme dietary modifications to lose weight can sometimes have very low BUN levels in the blood. Drinking way too much water (psychogenic polydipsia) can also give very low BUN and creatinine ratio in the blood tests.
Yes, in fact, one of the commonest causes of high BUN in the blood is a very high protein diet. If someone is working out extensively to gain weight, he/she is likely ingesting a very high protein amount (almost 2-3 g/kg/day). In these cases, a lot of nitrogenous waste is produced due to the protein breakdown, leading to ammonia generation that is eventually converted into urea.
Since urea is non toxic, it is eliminated via urine. Now, generally speaking, a high protein diet will also cause muscle gain, and hence the blood creatinine level will eventually rise and catch up, normalizing the BUN: creatinine ratio. Thus, high protein intake can cause a high BUN/Creatinine ratio but only initially. Again, if the same person is working out a lot and does not hydrate quickly, the BUN to creatinine ratio will be higher.
Yes, diuretics typically do. Commonly used for water retention, this class of medications can elevate the BUN and creatinine levels. Hence, patients using diuretics should get laboratories done to assess electrolyte and renal function levels periodically.
As mentioned above, in healthy adults, a high BUN: Creatinine ratio, particularly if it is > 20 is a sign of inadequate hydration. If you are exercising regularly and sweating a lot, you will likely get dehydrated fast.
One of the best ways to stay rehydrated during exercise is by using electrolyte rich hydration such as MAGNAK. This electrolyte powder delivers magnesium, sodium and potassium, all electrolytes depleted with exercise. Magnesium potentiates sodium delivery to exercising muscles and helps retain potassium in the body, leading to better muscle function and lesser cramping.
As magnesium dilates the blood vessels, it can improve perfusion (blood supply) of the kidneys while exercising, and this will eventually translate to an improvement of the BUN: creatinine ratio.
Thus, in simple terms, an easy way to improve your BUN/Creatinine levels is by improving your hydration.
