Most healthy adults can safely consume up to 2 grams of protein per kilogram of body weight per day. For a 150-pound person, that works out to roughly 135 grams. Go beyond that ceiling consistently, and you start putting unnecessary strain on your kidneys and liver without gaining any additional muscle-building benefit.
That said, the line between “enough” and “too much” depends on your size, activity level, and kidney health. Here’s how to figure out where you stand.
The Baseline and the Ceiling
The Recommended Dietary Allowance for protein is 0.8 grams per kilogram of body weight, which supplies only about 10% of your total daily calories. That number represents the minimum to prevent deficiency, not the amount most people should aim for. For a 180-pound person, the RDA comes out to about 65 grams, roughly the protein in two chicken breasts.
Active adults and athletes need more. Endurance athletes do well at 1.2 to 1.4 grams per kilogram, and strength-trained athletes benefit from 1.6 to 1.7 grams per kilogram. Research consistently shows that 1.6 grams per kilogram combined with resistance training is enough to maximize gains in lean mass, muscle strength, and overall performance in healthy young adults. Going above 2 grams per kilogram hasn’t been shown to offer additional muscle-building benefits.
Here’s a quick reference for the 2 g/kg upper range based on body weight:
- 130 lbs (59 kg): ~118 g protein/day
- 150 lbs (68 kg): ~136 g protein/day
- 180 lbs (82 kg): ~164 g protein/day
- 200 lbs (91 kg): ~182 g protein/day
What Happens When You Eat Too Much
Your body doesn’t store excess protein the way it stores fat or carbohydrates. When you eat more than your muscles can use, the liver converts the extra amino acids into urea and other waste products, which your kidneys then filter out. A single high-protein meal temporarily spikes your kidney filtration rate, a phenomenon called hyperfiltration. That’s normal and harmless in the short term.
The concern is chronic overload. When you consistently push past what your kidneys can comfortably process, the filtration rate stays elevated and the kidneys physically enlarge to keep up. In people who already have reduced kidney function, this creates a cycle where the remaining healthy tissue works harder, deteriorates faster, and leaves even less functional capacity. If you have healthy kidneys, this process is unlikely to cause problems at reasonable intakes. But if you have any degree of kidney disease, even undiagnosed, sustained high protein intake can accelerate the decline.
The liver has its own ceiling. It can metabolize roughly 285 to 365 grams of protein per day. In extreme scenarios where nearly all calories come from lean protein with almost no fat or carbohydrates, you get a condition historically called “rabbit starvation” or protein poisoning. This happens when protein exceeds about 45% of total calorie intake, which would mean eating around 500 grams of protein on a 2,000-calorie diet. At that point, ammonia and urea build up in the bloodstream faster than the body can clear them. This is rare and essentially impossible on a normal mixed diet, but it illustrates that the body has hard metabolic limits.
Signs You’re Overdoing It
Persistently bad breath is one of the more distinctive signals. When your body can’t break down amino acids efficiently, the excess combines with bacteria in your mouth to produce sulfur compounds that smell noticeably foul. This isn’t the same as garlic breath or morning breath. It’s a persistent chemical odor that doesn’t improve with brushing.
Other signs are less specific but worth noting: chronic dehydration (your kidneys need more water to flush out the extra urea), digestive discomfort like bloating or constipation (especially if the extra protein is displacing fiber-rich foods), and unexplained fatigue. Some people also notice darker urine, which reflects the kidneys working harder to concentrate waste products.
Your Protein Source Matters
The “how much is too much” question changes depending on where your protein comes from. A large study found that people who ate the most protein overall while maintaining a higher ratio of plant to animal sources saw a 28% lower risk of cardiovascular disease and a 36% lower risk of coronary heart disease compared to those who ate less protein with more animal-heavy ratios.
The average American eats plant and animal protein at roughly a 1:3 ratio. Shifting that closer to 1:2 significantly improves heart health outcomes, and coronary heart disease risk continues to drop as plant protein makes up an even larger share. This is partly because plant proteins come packaged with fiber, antioxidants, minerals, and healthier fats, while high-animal-protein diets often bring extra saturated fat and sodium along for the ride.
So 150 grams of protein from a mix of lentils, chicken, Greek yogurt, and tofu is a very different metabolic experience than 150 grams from processed meat and whey shakes alone.
Spreading It Out Through the Day
Your muscles can only use so much protein at once for repair and growth. Research suggests that 20 to 25 grams per meal is roughly the threshold for maximizing muscle protein synthesis in younger adults. Eating 60 grams in one sitting won’t harm you, but the excess beyond what your muscles can immediately use gets oxidized for energy or converted to other compounds rather than building tissue.
The practical recommendation is to spread your total intake across four meals, aiming for about 0.4 to 0.55 grams per kilogram at each one. For a 150-pound person targeting 100 grams daily, that’s roughly 25 grams per meal. This pattern appears to be more effective for lean tissue building than loading most of your protein into dinner, which is how many people eat.
The Bone Health Question
You may have heard that high protein intake leaches calcium from bones. Earlier research raised this concern because protein metabolism produces acid, and the body does pull calcium into the urine to buffer that acid. But more recent evidence tells a more complete story. High protein intake also increases calcium absorption in the gut and raises levels of a growth factor (IGF-1) that supports bone formation while lowering a hormone that breaks bone down. These benefits appear to offset the calcium loss in urine.
Multiple long-term studies now show that higher protein intake is actually associated with greater bone mineral density and fewer fractures. So within the 2 g/kg ceiling, protein is more likely helping your bones than hurting them.
Finding Your Personal Number
Multiply your weight in kilograms by the appropriate factor for your activity level. If you’re lightly active, aim for 1.0 to 1.2 g/kg. If you exercise regularly, 1.2 to 1.6 g/kg. If you’re doing serious strength training, 1.6 to 2.0 g/kg. Stay at or below 2 g/kg unless you’re working with a dietitian who has a specific reason to push higher.
If you have kidney disease, diabetes, or a family history of kidney problems, your safe ceiling is lower than the general population’s, and protein intake is something to discuss with your care team. For everyone else, the realistic danger zone isn’t the 130-gram range that fitness culture worries about. It’s the extreme end, above 2 g/kg sustained over months or years, where the risks start to outweigh any conceivable benefit.