If you’ve had a calcium-based kidney stone—or you’re trying to avoid getting another one—then it’s time to talk about sodium. Many people are surprised to learn that sodium plays a major role in stone formation. In this post, we’ll explore how sodium affects your risk, what the sodium recommendations are for kidney stone prevention, and how to begin tracking and reducing your intake.
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Why Does Sodium Matter for Kidney Stones?
The biggest issue with sodium is that it causes your kidneys to excrete more calcium into the urine. When your kidneys filter out sodium, they often filter out calcium alongside it. The more calcium in your urine, the greater your risk of forming calcium-based stones—particularly calcium oxalate or calcium phosphate stones.
If you’re trying to prevent stones, reducing your urinary calcium is key—and one of the most effective ways to do that is by eating less sodium.
Sodium Recommendations for Stone Prevention
The Dietary Guidelines for Americans recommend consuming less than 2,300 mg of sodium per day. This recommendation aligns with what we advise for kidney stone prevention as well.
But here’s the reality: the average American far exceeds that amount.
- The average intake is just over 4,000 mg per day for men
- For women, it’s just under 3,000 mg per day
That means the vast majority of people have room to improve—less than 21% of adults in the U.S. stay below the recommended 2,300 mg/day.
Using Your 24-Hour Urine Test
Your 24-hour urine test is one of the best tools for assessing your sodium intake. It provides a measurement of sodium in millimoles (mmol) per day. Here’s a handy conversion:
- 150 mmol = 3,450 mg
- 125 mmol = 2,875 mg
- 100 mmol = 2,300 mg (the recommended upper limit)
- 75 mmol = 1,725 mg
- 65 mmol = 1,500 mg
- 50 mmol = 1,150 mg
Even if your urine sodium result appears within the lab’s “normal” range, if it’s above 100 mmol/day, you may benefit from lowering it further. In some cases—depending on your health status—it may be helpful to aim for around 65 mmol/day (or 1,500 mg of sodium).
Can’t I Just Look at My Blood Sodium?
Unfortunately, no. Your blood sodium levels are not a reliable indicator of how much sodium you eat.
Sodium is involved in several vital processes:
- Muscle contraction (including the heartbeat)
- Nerve function
- Acid-base balance
- Blood pressure regulation
- Fluid balance
Because of its many roles, your body tightly controls blood sodium levels. Even if you’re eating far too much or too little sodium, your blood sodium may appear completely normal. That’s why we look at 24-hour urine sodium to assess intake.
Salt vs. Sodium – What’s the Difference?
These terms are often used interchangeably, but they aren’t exactly the same. A lot of people think that they are following a low sodium diet simply by not using their salt shaker. If that is your strategy, you are probably NOT following a true low sodium diet.
Table salt is a made up of sodium and chloride, and we do need to reduce our sodium, but sodium sneaks into far more thing that just your salt shaker.
When we talk about “low-sodium diets,” we’re referring to total sodium from all sources—not just what comes from your salt shaker. This is where scrutinizing other foods in your day will be important.
Where Does Sodium in the Diet Come From?
You might be surprised to learn that only a small portion of sodium in the typical American diet comes from the salt shaker.
Here’s where sodium tends to come from:
- Less than 5% from salt added at the table
- 6% from salt used during cooking
- 14% from naturally occurring sodium in foods (mostly in animal products)
- 71% from salt added outside the home (restaurants, processed foods, prepared meals)
That last category is the biggest contributor by far. Even if you never use your salt shaker, you could still be getting 4,000–5,000 mg of sodium per day if you rely on restaurant food, convenience meals, or processed items.
Examples of Salt Added Outside the Home
- Restaurant meals (including fast food and fine dining)
- Prepared or hot foods from grocery stores and gas stations
- Packaged and processed foods like soups, cold cuts, chips, frozen meals, breads, and condiments
How to Find Out How Much Sodium You’re Eating
If you’re just getting started with a kidney stone diet or trying to follow a lower sodium diet, one of the most useful things you can do is track your intake for a day.
This gives you a realistic picture of where you’re starting so you can make informed changes.
How to Track Your Sodium
Use a food tracking app like Cronometer or another app that shows detailed sodium data. Many offer free versions or trials. Log your food for an entire day and pay attention to the total sodium.
Tips for Accurate Logging
- Be specific – Choose the exact brand or product if possible
- Log manually – If you can’t find the food, use the custom entry option
- Measure accurately – Read package labels and consider using a food scale
- Log in real time – Waiting until the end of the day may cause you to forget details, which can lead to underestimating your intake
Once you’ve tracked a full day, you’ll have a better sense of how much sodium you’re currently eating—and how far off you are from the 2,300 mg goal.
From there, you can begin using specific strategies (which we’ll cover in future blog posts and videos) to start lowering your intake without sacrificing flavor or satisfaction.
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