Why Does My Poop Smell Like Metal?

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A comprehensive look at stool odors and what they mean

Co-authored by Muhammad Khan, MD, MPH and Eric McClure

Last Updated: May 1, 2024 Fact Checked

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• Why does my poop smell like metal?
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• Is my smelly poop a medical concern?
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• Preventing Smelly Poop
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• Why does my poop smell like rotten eggs?
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• Why does my poop smell like ammonia?
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• Expert Interview

|Show more |Show less

Your bowel movements tell you a lot about what’s going on in your body, so you’re probably alarmed if your stool has suddenly developed a metallic odor. Breathe easy, though—in most cases a slightly metallic or rust-like odor isn’t a particularly big deal. But still, it’s probably worth investigating. In this article, we’ll help you figure out why your stool is smelling strangely. We’ll also cover the other common stool odors you might run into based on your diet and gut bacteria.

Things You Should Know

• Stool typically smells like metal because of excess iron, which is used to create the hemoglobin in your red blood cells.
• If you see bright red blood along with the metal smell, don’t worry. It’s probably a minor issue (like hemorrhoids), although you should see a doctor soon to be safe.
• Dark red or black blood is serious, since it indicates you’re bleeding further up in your digestive tract. See a doctor ASAP, especially if you have stomach pain.

Steps

Section 1 of 5:

Why does my poop smell like metal?

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1. 1
   Metallic odors are usually a sign there’s excess iron in your stool. Iron is essential for making hemoglobin—the primary protein in red blood cells. As a result, blood has a metallic odor, which is probably what you’re smelling in your stool. Don’t worry though, this is surprisingly common and probably not serious. Here's what you should look out for and what you should do next:

   • Bright red blood in the water or on the toilet paper: This means you’re bleeding near your rectum. This is usually due to something like a minor cut, anal fissures, or hemorrhoids, which are no big deal. Though, if your stomach hurts or you feel lightheaded, you should see a doctor.
   • Dark red blood or black, tarry material on your stool: This means that you're bleeding further up in your stomach or intestines. Though this is an unlikely case, it could be something more serious, from an ulcer to stomach cancer. You'll want to see a doctor ASAP.
   • No blood in your stool: In this case, the iron smell isn't from blood and is likely just caused by a harmless diet change. We'll walk through the specifics directly below.
2. 2
   The metallic odor could be due to something you ate. If your stool looks normal and brown but it still smells like metal, you’ve likely eaten something that was really high in iron. This is especially common with people on a Paleo diet. It’s no big deal, so don’t worry about it unless it continues to smell like metal after you change your diet. Foods high in iron include:

   • Red meats, like beef, lamb, or veal (the redness of meat is actually iron)
   • Offal (liver, kidney, pate)
   • Chicken, fish, and eggs
   • Dried fruits, nuts, oats, tofu, and wholewheat pasta and bread
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3. 3
   The smell may be coming from supplements or medication. A lot of antibiotics seem to cause a metal-like odor in your stool. Beyond that, if you’re taking any kind of daily vitamin or supplement that contains iron, that’s probably the source of the odor.

   • Antibiotics kill bacteria, so your stool often ends up just smelling like iron because everything else has been removed.
   • Any antibiotic can cause this odor, although metronidazole seems to be the most common culprit. Any blood thinner medication can also cause a metallic odor in your stool.
   • You should ask your doctor about the odor, but it’s probably no big deal if it’s a byproduct of a vitamin or medication.
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Section 2 of 5:

Is my smelly poop a medical concern?

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1. 1
   Get it checked out, but it’s not an emergency for bright blood or odors alone. Bright red blood in your stool points towards hemorrhoids, which are swollen veins in the rectum, or anal fissures, which are cracks in the lining of the anus. You need treatment, but it’s not a serious “go right now” situation. If there’s no blood but the odor goes away with a change in your diet or medication, you’re fine so long as you don’t have any other symptoms.

   • If you do have other symptoms, such as fatigue, lightheadedness, or stomach pain, see a doctor ASAP.
   • The other common potential causes of bright red blood include irritable bowel disease, rectal polyps, diverticular bleeding, colorectal damage, and irritation from anal sex. A doctor should take a look, but these conditions are usually more annoying than they are dangerous for your health, so don’t worry.
2. 2
   See a doctor if your stools are black and tarry, or the odor persists. Black and tarry stools are a sign that you may have internal bleeding, so see a doctor ASAP—especially if you’re lightheaded or in pain. Beyond that, you should also see a doctor if the odor is extremely Italic text'Place bold text herenoticeable and it doesn’t go away with a change in diet or medication. It’s likely nothing, but extremely smelly stools can be a symptom of:

   • Malabsorption
   • Crohn's disease
   • Celiac disease
   • Infection
   • Pancreatitis
   • Cancer
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Section 3 of 5:

Preventing Smelly Poop

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1. 1
   Eat a diet that contains slightly less sulfur. Sulfur is primarily found in dried fruits and root vegetables, so just don’t overdo it with the cabbage, potato, garlic, onion, kale and dried fruit. All of these foods are fine for you, but if you’re consuming so much sulfur that your stool is smelling like eggs, it’s totally fine to cut back a bit.

   • You might have noticed that sulfur-rich foods are all “healthy” food. That’s no coincidence. Sulfur-rich food is very good for you, and your body needs sulfur to function. If you’re consuming so much sulfur that your body can’t process it though, you’re getting more than enough.
2. 2
   Get more fiber in your diet. Women need 21-25 grams of fiber a day, while men typically need 30-38 grams. You can get fiber from fruit, green vegetables, or whole grains. Fiber regulates your gut bacteria and helps your digestive track develop and produce stool, so increasing your fiber consumption should help with any loose, uncomfortable, or irregular stools you’re experiencing.

   • You can also consume a psyllium husk supplement in the form of a powder or pill to ensure your gut gets its daily dose of fiber on a regular schedule.
3. 3
   Increase your water intake to stay hydrated. Drink water with (and after) your meals and aim to drink around 6-8 glasses a day. A lot of the bacteria and microbes in your stool end up leaving your body as poop because they weren’t absorbed in the gut, and water makes that digestive process easier. Not only will you feel better when you’re hydrated, but your stools will be less smelly as well!

   • If you struggle to drink enough water because it’s just too dull for you, try adding some fresh citrus fruit to some ice water. Soda water is also another phenomenal alternative.
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Section 4 of 5:

Why does my poop smell like rotten eggs?

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1. Rotten egg odors come from sulfurous foods or bacteria. A rotten egg odor is almost positively sulfur, and it’s common in a lot of foods and beverages. If you don’t have diarrhea, you probably just ate a lot of sulfur. If you do have diarrhea, that smell is probably giardiasis—an infection caused by contaminated food or water. See a doctor to get some antibiotics.

   • Foods rich in sulfur include carrots, onions, cabbage, broccoli, cauliflower, and potato.

Section 5 of 5:

Why does my poop smell like ammonia?

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1. Ammonia fumes are a sign your digestive bacteria are imbalanced. Bacterial overgrowth in your intestines can occur for a variety of reasons. In most cases, it’s something mundane like a dietary change. However, it can also

   • If you only notice the ammonia odor for nothing to worry about.
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