What's this test for?

This test is ideal if you're experiencing ongoing, unexplained diarrhea that hasn't gone away with typical dietary changes. It measures sodium and potassium in your stool to help figure out whether your diarrhea is caused by a problem with fluid absorption or by something in your diet or gut that's pulling in extra water. Knowing this can point you toward the right next steps for figuring out what's actually going on.

What's included in this test?

This panel looks at the balance of electrolytes in liquid stool along with a calculated osmotic gap. These measurements matter because they help distinguish between diarrhea caused by the gut secreting too much fluid versus diarrhea caused by something in the intestine drawing in water, which points toward very different underlying causes.

What happens after I get my results?

Your results will show up in your account with the sodium, potassium, and calculated osmotic gap values, along with what a normal range looks like for each. Depending on whether your gap suggests a secretory or osmotic pattern, next steps might include reviewing your diet for sugar substitutes or laxatives, cutting out suspected trigger foods, or seeking further evaluation if diarrhea continues or worsens. A downloadable lab report is available in your account, and you can track this result over time using the trends feature if you retest later.

When will I get my results?

Results are typically available within about 7 days of your sample being processed at the lab. You'll get a notification once your report is ready to view in your account. If your results are still pending past that window, you can check your account status directly.

Who should consider this test?

This test is a good fit for anyone dealing with chronic diarrhea that has lasted weeks without a clear cause. It's also useful if you've noticed diarrhea patterns linked to certain foods, sugar substitutes, or supplements and want more information before ruling things in or out. People who have already tried simple dietary changes without improvement often find this test helpful for narrowing down the cause.

What symptoms indicate I may need this test?

Watch for persistent loose or watery stools lasting more than a couple of weeks, especially if it's not tied to an obvious short-term illness. Other signs include diarrhea that changes with certain foods, unexplained weight loss, or diarrhea that continues even when you're fasting or not eating. If you're seeing blood in your stool, severe dehydration, or a high fever, seek medical care right away rather than waiting on test results.

How can I naturally support healthy digestion while dealing with diarrhea?

Staying well hydrated with water and electrolyte drinks is one of the most important things you can do, since diarrhea depletes both fluids and minerals. Temporarily cutting back on sugar alcohols (like sorbitol and mannitol), artificial sweeteners, and high-lactose dairy can help if osmotic diarrhea is suspected. Eating bland, low-fiber foods like rice, bananas, and toast can also give your gut a chance to settle down.

What is the osmotic gap and why does it matter?

The osmotic gap is a calculated number that compares your stool's electrolyte content to its overall fluid-drawing power. A high gap suggests something other than electrolytes, like unabsorbed sugars, is pulling water into your gut, pointing to osmotic diarrhea. A low gap suggests your gut itself is secreting excess fluid, pointing to secretory diarrhea, which often has a different set of causes.

What causes an abnormal osmotic gap?

A high osmotic gap is often linked to things like lactose intolerance, sugar substitutes in foods or gum, certain laxatives, or malabsorption issues. A low osmotic gap is more often tied to infections, hormone-related conditions, or issues with how the intestine absorbs and releases fluid. Reviewing your recent diet, medications, and supplement use can help you spot likely triggers before considering further testing.

What should I do if my results are abnormal?

If your osmotic gap points to osmotic diarrhea, try eliminating common triggers like sugar-free products, dairy, or certain supplements for a week or two and see if symptoms improve. If it points to secretory diarrhea, especially if diarrhea is severe, persistent, or accompanied by fever or weight loss, it's important to seek medical care promptly since this pattern can be linked to infections or other conditions that need direct evaluation. Keep a symptom and food diary in the meantime to help identify patterns.

Getting your blood test with us is easy, private & backed by the power of science.Long story short: In the test options, use the filters or search box to narrow your choices and find the test you want. If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test. Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout. If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want. When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system. Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way. You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy! If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.

How do I know which test to get?

In the test options, find the test you want. If you’re not sure which test to get, we can lend a hand in finding the right option. Just text or call us at 754-799-7833, email us at support@privatemdlabs.com, and we'll gladly help you. We've got your back and reply quickly.

When will my lab results be available?

Most test results will be available within 1–3 business days. Once they're ready, we'll send an email and text message to let you know. After your blood draw, just hang tight and don't worry – we'll keep you updated and in the loop! If you have any further questions, please text us at 754-799-7833 or email support@privatemdlabs.com, and we'll gladly help you.

Is it possible to make changes to my lab order if I made a mistake with the name, date of birth, or any other details?

Absolutely! We totally understand that errors can happen. No worries, we're here to help you. Just reach out to us via text at 754-799-7833 or shoot us an email at support@privatemdlabs.com. Remember to include your order number and let us know the correct information you’d like to update. Our awesome team will jump right in and make sure everything is sorted out and accurate for you. There are no changes necessary if your address is wrong on the requisition though. We don’t mail anything out. Our lab requires an address to be listed to generate an order.

Do you accept health insurance?

Only HSA & FSA is accepted. Our services are strictly self-pay and cannot be submitted to your health insurance provider except for Health Savings Accounts or Flexible Savings Accounts. This policy applies to all insurance companies, including federal health insurance programs like Medicare. If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com.

Can I cancel my order?

Yes. We get it – sometimes your needs change. As long as your samples haven’t been collected yet, we’re happy to help you cancel your order. If you have any further questions, please text us at 754-799-7833 or email support@privatemdlabs.com. You can read more about our cancellation policy here.

How can I find a lab location near me?

During the ordering process, you’ll be able to select a specific lab near you, with no strings attached! You can switch it up later easily and visit any of our authorized locations as long as it’s the same lab company you selected your test for (Quest Diagnostics or Labcorp). Before you proceed with your order, feel free to browse through all our lab locations here. This will give you the peace of mind of knowing that there's a lab nearby your home, office or your favorite gym. If you have any questions, please text us at 754-799-7833 or email support@privatemdlabs.com and we'll gladly help you.

Osmotic Gap Feces Test - Chronic Diarrhea Causes

Getting your blood test with us is easy, private & backed by the power of science.

Long story short:

In the test options, use the filters or search box to narrow your choices and find the test you want.
If you need a hand navigating through options, text our super friendly support team at 754-799-7833, and we'll provide tailored suggestions to help you find the ideal test.
Once your order is placed, we’ll create your doctor’s lab order remotely, without any need for you to make a trip to a doctor in person or to talk to the doctor. Expect to receive your doctor’s lab order right in your inbox. It will also be in your patient portal if you need to find it later. We’ll also include instructions regarding fasting and other requirements for your test. Your patient portal will be auto-created hassle-free during checkout.
If this is your first time ordering, you'll be prompted to create a password for instant login access to your patient portal. It's a quick way to conveniently access your orders and results whenever you want.
When you’re ready, visit one of our 4,000 locations. Just bring your ID – no printing or faxing of your lab order is needed, as your order and details will already be in the lab system.
Note that most lab locations don’t accept walk-ins, so it’s best to book an appointment in advance. Don’t worry – we’ll provide detailed instructions along the way.
You’ll get your results via email & SMS and dive into understanding your body better. Yup, that easy!

754-799-7833

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