High blood urea and creatinine levels signal that your kidneys aren’t filtering waste as efficiently as they should. Normal blood urea nitrogen (BUN) falls between 5 and 20 mg/dL, while creatinine ranges from 0.6 to 1.2 mg/dL for men and 0.5 to 1.1 mg/dL for women. Bringing these numbers down requires addressing the root cause, whether that’s diet, dehydration, medication side effects, or kidney disease itself.
Why These Numbers Rise in the First Place
Urea and creatinine are both waste products, but they come from different sources. Urea is produced when your body breaks down protein, either from food or from your own muscle tissue. Creatinine comes from the normal turnover of muscle cells. Both are filtered out by the kidneys, so when kidney function drops, both accumulate in the blood.
But kidney disease isn’t always the culprit. Urea can spike from eating a high-protein diet, from dehydration, from heart failure that reduces blood flow to the kidneys, or even from gastrointestinal bleeding (which releases protein into the gut for digestion). Creatinine can rise temporarily after intense exercise. One study found that a single session of exhaustive resistance training raised serum creatinine by nearly 12%, and levels remained about 2.5% above baseline even 24 hours later. If your blood was drawn the day after a brutal workout, the result may not reflect your actual kidney function.
Older adults are especially vulnerable to elevated levels because they tend to drink less water, often take diuretics, and may have underlying heart failure that reduces kidney perfusion. Understanding which of these factors is driving your numbers up makes a huge difference in how you bring them down.
Reduce Protein Intake Strategically
Since urea is a direct byproduct of protein metabolism, lowering protein intake is the single most effective dietary lever for reducing blood urea. For people with chronic kidney disease (CKD), low-protein diets of 0.6 to 0.7 grams of protein per kilogram of body weight per day have been recommended for over 70 years to slow disease progression and delay dialysis. For a 70-kilogram (154-pound) person, that works out to roughly 42 to 49 grams of protein daily, significantly less than the 80 to 100 grams many people eat without thinking about it.
For more advanced kidney disease (stages 3 through 5), some nephrologists prescribe very low-protein diets of just 0.3 to 0.4 grams per kilogram per day, paired with supplements called keto acid analogs that provide essential amino acids without the nitrogen waste. In one study, this approach delayed the need for dialysis by about 11 months compared to unrestricted protein intake. These very restrictive diets also reduced serum urea, phosphorus, and fasting glucose while maintaining markers of nutrition like albumin and muscle strength.
You don’t necessarily need to go that low. Even modest reductions help. Swapping a large steak for a palm-sized portion, replacing one meat-based meal with a plant-based one, and choosing lower-protein grains like rice over higher-protein ones like quinoa can meaningfully reduce the amount of urea your body produces each day.
Eat More Fiber
Fiber offers a surprising benefit for kidney health: it creates an alternative route for removing nitrogen waste from your body. When you eat enough fiber, particularly soluble types found in oats, beans, and fruits, the bacteria in your colon feed on it and multiply. As they grow, those bacteria absorb amino acids from the gut and incorporate them into their own cell structures. Those bacteria then leave your body in stool, taking the nitrogen with them. This effectively redirects waste that would otherwise need to be filtered by your kidneys.
A high-fiber diet also increases the production of short-chain fatty acids, compounds made by gut bacteria that support intestinal health and further promote this fecal excretion of nitrogenous waste. Both soluble fiber (from oats, barley, legumes, and citrus) and certain partially fermentable insoluble fibers contribute to this process, though soluble types are the most effective.
Stay Properly Hydrated
Dehydration concentrates waste products in your blood and reduces the rate at which your kidneys can filter them. Population studies consistently show that lower daily fluid intake correlates with faster annual decline in kidney filtration rate and higher risk of developing CKD. In animal models, increased water intake has been associated with less protein leaking into urine and slower kidney disease progression.
That said, there is no specific evidence-based fluid target for people with kidney disease. Drinking more water helps if you’re under-hydrated, but pushing excessive fluids can lower your blood sodium and raise your blood pressure. Studies of patients who drank very large volumes showed signs of “pushing diuresis,” with diluted urine but higher blood pressure and lower sodium. The practical takeaway: drink enough that your urine stays a pale yellow throughout the day, and talk to your doctor about any specific fluid restrictions if you have advanced kidney disease or heart failure.
Review Your Medications
Several common medications can raise creatinine by reducing blood flow to the kidneys or causing direct kidney inflammation. NSAIDs like ibuprofen and naproxen are among the most frequent offenders. They alter the pressure dynamics inside the kidney’s filtering units and can acutely raise creatinine, especially with regular use. Blood pressure medications like ACE inhibitors and ARBs can also cause a temporary bump in creatinine when first started, though they’re often protective for the kidneys in the long run.
Other medications known to affect kidney filtering include certain immune-suppressing drugs and some antibiotics. If your creatinine recently climbed, reviewing what medications or supplements you started in the preceding weeks is a practical first step. Even over-the-counter pain relievers and high-dose vitamin C or creatine supplements can influence your numbers.
Avoid Temporary Spikes Before Lab Work
If you’re tracking your kidney numbers over time, consistency in how you prepare for blood draws matters. Intense exercise within 24 hours of a blood test can artificially inflate creatinine. Eating a large, protein-heavy meal the night before can raise your BUN. Dehydration from skipping fluids in the morning can concentrate both values. For the most accurate picture of your kidney function, avoid heavy exercise for at least 24 to 48 hours before blood work, stay normally hydrated, and eat your usual diet rather than an unusually large or protein-heavy meal.
Supplements With Some Evidence
Chitosan, a fiber-like substance derived from shellfish shells, has shown some promise. In a study of 80 patients on long-term dialysis, chitosan supplements produced significant reductions in both serum urea and creatinine after four weeks. Patients also reported improved appetite, better sleep, and more physical energy after 12 weeks. The mechanism isn’t fully understood, and the study was conducted in people already on dialysis, so it’s unclear how well the results translate to earlier stages of kidney disease.
Some herbal supplements are marketed for kidney health, but most lack rigorous clinical evidence, and some can actually harm the kidneys. The safest approach is to focus on the dietary strategies with strong evidence (lower protein, more fiber, adequate hydration) and discuss any supplements with your nephrologist before adding them.
When the Cause Is Kidney Disease Itself
If your elevated urea and creatinine reflect genuine CKD rather than a reversible cause like dehydration or medication, the goal shifts from “fixing” the numbers to slowing the rate at which kidney function declines. The dietary and lifestyle strategies above all contribute to this. Controlling blood pressure and blood sugar (if you have diabetes) are the two most impactful medical interventions for preserving remaining kidney function.
The ratio between your BUN and creatinine can offer clues about what’s going on. A ratio close to 10:1 is typical in moderate to advanced kidney failure. A ratio significantly higher than that, where urea is disproportionately elevated, points toward dehydration, heart failure, GI bleeding, or excess protein intake as contributing factors on top of any kidney disease. This distinction matters because treating dehydration or adjusting diet can bring urea down quickly even when the underlying kidney function hasn’t changed.