“Eat to Your Labs”: A Kidney Dietitians Perspective


“Eat to Your Labs”: A Kidney Dietitians Perspective

If you’re navigating the world of kidney disease, you’ve likely come across the phrase ‘eat to your labs’ on social media. It’s a phrase commonly used when someone inquires about whether they can consume a specific food or not. For example: it seems logical that if blood potassium level is too high, one should avoid high potassium foods, but it’s not always so black and white. For many people people chronic kidney disease (CKD), majority of their labs outside of creatinine and estimated glomerular filtrate rate (eGFR) are normal – does this mean their nutrient intake is perfect?! Not quite! Read on as I uncover if you can or can’t simply just “eat to your labs”!

How often are labs checked with CKD?

Most people don’t look forward to blood draws but it is an important tool to monitor for kidney and overall health. Frequency of blood work is based on your stage of kidney disease and your risk factors for progression. Those with stage 1-3 CKD may get lab draws once or twice a year. In stage 4-5 CKD, labs may be drawn every 3 month or as frequency as monthly.

What routine labs are checked with CKD?

One set of labs drawn routinely by your doctor is called the basic metabolic panel (BMP). This lab test measures eight different substances in your blood: glucose, calcium, sodium, potassium, carbon dioxide, chloride, BUN and creatinine. Estimated glomerular filtration rate (eGFR) is often included as well, but it is actually a calculation, not a direct level from your blood. Another lab you may see measured is phosphorus. Phosphorus is not part of the standard BMP, but it is sometimes added in those with kidney disease.

Labs like sodium, potassium, calcium and phosphorus are also nutrients in our diet – so let’s take a look to see if we can or can’t “eat” to these values! Note: goal ranges for these labs vary based of lab company.

Sodium levels in CKD

What is a normal sodium level?

136 – 145 mEq/L

About blood sodium levels:

In our blood, sodium is an electrolyte that is most known for its role in nerve and muscle function and fluid balance. Sodium levels are most often used to assess our body’s fluid status. A low sodium level can indicate your body is holding on to too much fluid, which dilutes the sodium. On the other hand, a high sodium level often means dehydration, or there is not enough water in the body.

Can you “eat” to your sodium level?

If sodium is normal – NO.

A normal sodium level does not necessarily mean you’re eating the right amount of salt. Our kidneys and other systems in the body keep sodium levels in control by adjusting the amount of fluids in our body via urinating as well as amount of sodium kept in our body or excreted in the urine. As mentioned above, sodium is more related to our bodies fluid status. It is possible to have a high sodium intake yet have normal sodium levels.

If sodium is low or high- MAYBE, but typically not.

If sodium levels are too low or too high, fluid status is usually one of the first things evaluated by your healthcare provider. High sodium can occur with a high sodium diet, but as a dietitian with 14 years experience I can say this is rare and it’s usually related to dehydration. If your sodium level is low, your doctor may put you on a fluid restriction and likely have more testing done to determine the underlying cause.

Potassium levels in CKD

What is a normal potassium level?

3.5 – 5 mEq/L (upper limit may go up to 5.2 depending on your lab)

About blood potassium levels:

Potassium is another electrolyte in our blood and it works in tandem with sodium to help with nerve/muscle function and maintain fluid balance. It is also very important for heart health and blood pressure regulation. High potassium, called hyperkalemia, is a complication that is more common in those with CKD compared to those with normal kidney function. This is because our kidneys play a role in keeping our blood potassium normal. High potassium is dangerous as it can lead to irregular heart rhythms, which may result in a heart attack. Low potassium, which can also occur, is just as dangerous to your heart.

Can you “eat” to your potassium level?

If potassium is normal – not exactly.

A normal potassium level easily gives permission that one shouldn’t limit potassium. BUT a normal potassium level doesn’t automatically mean you are getting the optimal amount of potassium in your diet! Dietary potassium is vital for our health and most people are getting too little, even with CKD! Low potassium intake is associated with negative health outcomes such as increased risk of heart disease, kidney stones, poor bone health and even increased risk of type 2 diabetes. 

If potassium is high – Yes, but not in the long run.

High potassium levels (especially levels over 6) need to be treated as they can be dangerous. This likely includes limiting potassium in your diet. Contrary to popular belief, too many fruits, vegetables, beans and legumes are often not to blame for high potassium levels. Researchers have found there is little to no correlation with potassium intake from fruits and vegetables and blood potassium levels! Common causes of high potassium levels in those with CKD include blood pressure medications, certain diuretics, constipation, metabolic acidosis and intake of potassium salts.

If potassium is low – Yes.

Low potassium is also very dangerous and can cause a heart attack. Poor food intake can cause low potassium levels but it can also happen due to certain diuretics, losses from diarrhea/vomiting. If your potassium level is low, you should be eating more potassium to bring blood levels up to the normal limit.

Calcium levels in CKD

What is a normal calcium level?

 8.4 – 10.5 mg/dL – but with kidney disease, avoid calcium >10.2

About blood calcium levels:

Only about 1% of the body’s calcium is in the blood, the rest is stored in our bones. Besides bone health, calcium is vital for nerve and muscle function, blood clotting and hormones. Calcium is tightly regulated by the kidneys, gut, bones and certain hormones. Calcium regulation can become a problem with CKD, but this doesn’t occur until later stages of kidney disease.

Can you “eat” to your calcium level?

If calcium is normal? Not exactly.

Calcium levels often stay normal in early stages of kidney disease due to the fact our body does a good job at keeping it in the normal range. Your body quickly adapts with blood calcium levels fall by increasing calcium absorption in the gut and releasing calcium from the bones to the blood. Even though calcium is normal, it doesn’t necessarily mean someone is eating the right amount.

If calcium is high – maybe.

Dietary intake of calcium should be evaluated if levels are high, but too much cheese may not be the cause. Calcium supplements and excess intake of calcium fortified foods are more likely to elevate calcium levels. What we eat is often not to blame. High calcium levels can also occur due to excess vitamin D levels, bone disease, hyperparathyroidism and cancer. High calcium is dangerous as when levels are above goal, calcium can deposit in soft tissues and vessels.

If calcium is low – maybe.

Again, it’s important to evaluate dietary calcium intake when levels are low. But eating excess calcium may not be the right fix. Low calcium levels can occur with vitamin D deficiency, hypoparathyroidism and bone disease. It’s important to note that calcium is never evaluated alone. Your healthcare provider will also assess other factors, including intact parathyroid hormone, vitamin D, and phosphorus levels.

Phosphorus levels in CKD

What is a normal phosphorus level?

3-4.5 mg/dL (your doctor may set a goal up to 5.5 if you are stage 5)

About blood phosphorus levels:

Phosphorus is a mineral that is important in our body for bone health. 85% of our phosphorus is stored in our bones, the rest is found in the blood and other tissues. Our kidneys help regulate phosphorus levels in the blood.

Can I “eat” to my phosphorus level?

If phosphorus is normal? Not exactly.

You’re probably noticing a theme here… but again – normal phosphorus doesn’t mean your intake of phosphorus is “right” or “wrong”. Don’t make the mistake of seeing a normal phosphorus level as a sign to double your intake. Even until stage 5, phosphorus levels may be normal in CKD. Our body does a good job getting rid of extra phosphorus via the kidney thanks for a hormone called fibroblast growth factor 23 (FGF-23). Unfortunately, high FGF-23 has many negative side effects – it’s associated with increased risk of heart disease, decline in kidney function, poor bone health and more.

If phosphorus is high? Yes.

Dietary phosphorus should be addressed when blood levels are high. It’s important to consider the source of phosphorus. Phosphorus additives, found in packaged foods/drinks, are the biggest offenders for elevated blood levels. Phosphorus is also found naturally in animal products, like poultry, meats, fish, seafood and dairy and plant foods like whole grains, beans, nuts and seeds. Plant sources has the smallest impact on blood phosphorus levels as they are poorly absorbed.

It’s important to note that some people have high phosphorus due to non-dietary causes such as high levels of vitamin D and bone disease. Medications called phosphorus binders may need to be added when phosphorus levels can’t be controlled by the diet.

If phosphorus is low? Yes.

Low phosphorus may warrant diet adjustments as well, although true deficiency of this mineral is very rare as it’s found in virtually all foods. A low level can occur due to vitamin D deficiency, bone disease, parathyroidectomy and medications. Your practitioner should work with you to figure out underlying cause and implement necessary interventions.


Your labs are important to monitor and track for kidney disease, but they usually aren’t the best measure of your actual nutrient intake. Our body is able to maintain normal levels sometimes even until stage 5 kidney disease. When labs are out of range, they should be addressed. Working with a kidney dietitian can use your labs and medical history to determine your nutrients labs to keep or get your labs in range!

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Meet Lindsay

Registered dietitian and board certified specialist in renal nutrition