Do Iron Pills Cause Constipation? A Closer Look

Many people fall short on essential mineral iron from diet alone. Supplements can have a big impact by restoring healthy iron levels, and in doing so support blood health, oxygenation of organs and tissues, and ultimately, energy.

As helpful as taking iron supplements can be for health, some individuals often encounter an unwelcome digestive side effect and wonder: Does iron cause constipation?

In some cases, yes it does. But there are steps you can take to avoid digestive side effects while still getting iron benefits.

This article delves into the connection between iron and constipation, exploring why this side effect occurs, who might be at risk, and practical tips to manage constipation while ensuring you get the iron your body needs. Let's get to it!

Key Takeaways

• Benefits of iron: Dietary iron and iron supplements support blood health, immune function, oxygenation of organs and tissues, and ultimately, energy levels.
• Iron deficiency is common: Many people do not get enough iron from their diet alone, making iron supplements important for restoring healthy levels.
• Symptoms of iron deficiency: Iron Deficiency Anemia (IDA), muscle weakness, fatigue, impaired cognition, poor immunity, shortness of breath, poor concentration, and restless legs syndrome.
• Iron and constipation: Iron supplements can cause constipation and stool hardening. Certain strategies can help, including taking the right forms of iron and highest-quality supplements.
• Increasing prebiotic fiber intake and staying hydrated can help ease constipation and maintain regularity. We recommend a good prebiotic at the end of this article.
• Iron absorption tips: Iron is best absorbed with vitamin C-rich foods and on an empty stomach, while avoiding calcium-rich foods, tea, and coffee at the same time.
• Dietary Sources of Iron: Key sources include red meat, fortified orange juice, seafood, beans, lentils, spinach, fortified cereals, tofu, pumpkin seeds, quinoa, and dark chocolate.
• Forms of iron in diet: Dietary iron comes in two forms, heme (animal sources) and non-heme (plant sources), with heme iron being more efficiently absorbed.
• Types of Iron Supplements: Options include standalone iron supplements like ferrous sulfate, ferrous gluconate, ferrous fumarate, iron bisglycinate, carbonyl iron, and liquid iron supplements.

What Is Iron?

Elemental iron is an essential nutrient that must be obtained from the diet. Iron is a vital mineral for producing hemoglobin, the protein in red blood cells that carries oxygen throughout the body.

It supports energy production, immune function, and cognitive development. Iron is also crucial for the synthesis of certain hormones and connective tissues.

Without adequate iron, the body can't produce enough red blood cells, leading to conditions like iron deficiency anemia, which causes fatigue, weakness, and shortness of breath. Iron supplements can support the adequate intake that is necessary for maintaining overall health and well-being.

But despite its prevalence in a wide variety of plant and animal foods - in the form of non-heme and heme iron, respectively, it remains one of the world’s most prevalent nutrient deficiencies, affecting an estimated 20-25% of the world’s population.⁽¹⁾

The Centers for Disease Control and Prevention (CDC) states that iron deficiency is a common cause of anemia that can affect overall health.

A blood test administered by your healthcare professional can determine if you are deficient and require iron supplements.

Meeting iron intake requirements is more challenging for vegans and vegetarians due to dietary restrictions and absorption issues. Naturally, the easy fix is to maximize absorption using nutritional hacks, iron pills and supplements with iron.

Did you know?

*People with inflammatory bowel diseases (IBD) are at higher risk of iron deficiency due to chronic intestinal bleeding and inflammation. Those with inflammatory bowel disease may require careful management of iron supplementation, including the potential use of intravenous iron to avoid exacerbating symptoms.

*Weight loss surgery, particularly procedures like gastric bypass, can lead to iron deficiency due to reduced stomach acid and altered digestion, impairing iron absorption and necessitating lifelong supplementation and monitoring.

If you’ve become backed up since starting your iron pills, you’re not alone - iron-induced constipation is a thing, and we’re giving you the details on why it happens.

Dietary iron is found in two forms: heme and non-heme iron.

Heme iron is derived from animal sources and has a higher bioavailability than non-heme derived from plant sources.

Although both types of iron are abundant in various food sources, the metabolization of iron differs, which accounts for their different absorption rates.

Heme iron is absorbed more efficiently from the gastrointestinal system because specific heme transporters enable it to pass directly across cell membranes and enter the bloodstream.

Nonheme iron, however, cannot use these transporters, so it requires conversion from ferric iron to ferrous iron before it can be absorbed.⁽²⁾

Once absorbed, iron is required for several essential physiological functions, including:⁽³⁾

• DNA production
• Enzyme synthesis
• Oxygen transport
• Red blood cell production
• Metabolism
• Immune function ( learn more about immune-enhancing foods)

Low iron status because of insufficient intake or absorption can lead to depletion of iron stores and, subsequently, iron deficiency anemia (IDA).

Iron deficiency anemia is associated with impaired physical, cognitive, and immune development and function.

Even without confirmed IDA, low iron levels can lead to nasty symptoms, such as fatigue, muscle weakness, cognitive impairment, and poor immunity.

Want more reasons to take iron supplements? Let's take a look at this mineral's many benefits.

Why Iron Is Important

1. Supports energy production

Iron is the primary component of hemoglobin, myoglobin, cytochromes, and various enzymes in myocytes that are critical for the transport and metabolism of oxygen for aerobic energy production during exercise.⁽⁴⁾

It’s also needed to produce adenosine triphosphate (ATP) in the electron transport chain; this component of energy production relies heavily on non-heme enzymes and heme-containing cytochromes.⁽⁵⁾

Low iron status is associated with poor aerobic power, with the magnitude of performance impairments dictated by how severe iron deficiency is.

Learn more about natural supplements for tiredness

2. Enhances immune function

Vitamin C, vitamin D, and zinc are staples for immune function, but iron is just as crucial for supporting the development and maintenance of the immune system.⁽⁶⁾

Iron deficiency affects the capacity of the immune system to mount an appropriate immune response to pathogens due to its involvement in cell proliferation and maturation, especially for lymphocytes.

3. Improves muscular performance

Are you struggling to get through your workout and find your muscles tapping out on you? Due to its role in energy production, iron deficiency can interfere with proper muscular performance and accelerate the onset of fatigue.

A 2003 study of twenty women with low iron status found that iron supplementation improved muscle fatigability, suggesting a direct role of iron in the extent of muscle fatigue experienced during physical activity.⁽⁷⁾

You can take iron supplements with a pre-workout focus (we recommend one below) to address this issue.

4. Regulates body temperature

Being constantly cold and dealing with freezing feet could signal that you’re iron deficient. Poor temperature regulation suggests low iron status due to its role as a cofactor in mechanisms involved in metabolism and thermoregulation.⁽⁸⁾

Research shows that iron-deficient people have impaired temperature regulation because of interference with heat production and heat loss rates.⁽⁹⁾

Impaired heat production typically stems from thyroid dysfunction, while an increased rate of heat loss stems from competing demands for tissue oxygenation versus reduced blood flow to mitigate heat loss.

Additionally, iron’s role in hemoglobin production - oxygen transport and tissue oxygenation - supports heat conservation and generation.

Low iron and hemoglobin levels can cause poor tissue oxygenation, which reduces heat production, increases loss, and interferes with normal thyroid function. As such, you become more sensitive to cold.

The Basics Of Iron Deficiency: Signs And Symptoms

Iron deficiency symptoms aren’t always the most obvious until stores are already too low, when they are typically confirmed with blood tests.

For people in iron deficiency territory, it can result in impaired physical performance, developmental delays, cognitive impairment, and adverse effects on pregnancy.⁽¹⁰⁾

Once iron deficiency reaches iron-deficiency anemia, functional disabilities become more apparent. Some of the most common symptoms of not getting enough iron include:

• Muscle weakness and fatigue
• Impaired cognitive function - learn about vitamins that are good for the brain
• Compromised immune function
• Pregnancy complications
• Low energy
• Shortness of breath
• Poor concentration
• Difficulty regulating body temperature
• Heart palpitations
• Headaches
• Hair loss
• Pica
• Restless legs syndrome

Iron deficiency takes time to develop, but if you’re not consuming enough through diet or supplementing, it can leave you at high risk - especially for vegans and vegetarians.

So, what’s the solution? First, try to increase iron in your diet. Then, invest in a good iron supplement. We're about to cover both. Let's get to it!

Dietary Iron Sources and Their Iron Content

Increasing your intake of iron rich foods is a great starting point for getting your status back up to par. Here are 10 foods that supply iron to consider incorporating into your diet:

1. Red Meat (Beef, Lamb). Serving Size: 3 oz; Iron Content: 2.1 - 2.7 mg
2. Fortified Orange Juice. Serving size: 8 oz; Iron Content: 3 mg
3. Seafood (Oysters, Clams, Mussels). Serving Size: 3 oz. Iron Content: 3 - 5 mg
4. Beans and Lentils. Serving Size: 1 cup, cooked. Iron Content: 3.3 - 6.6 mg
5. Spinach, green leafy vegetables. Serving Size: 1 cup, cooked. Iron Content: 6.4 mg
6. Fortified Cereals. Serving Size: 1 cup; Iron Content: 18 mg
7. Tofu. Serving Size: 1/2 cup; Iron Content: 3.4 mg
8. Pumpkin Seeds. Serving Size: 1 oz (about 85 seeds); Iron Content: 2.5 mg
9. Quinoa. Serving Size: 1 cup, cooked; Iron Content: 2.8 mg
10. Dark Chocolate (70-85% cocoa). Serving Size: 1 oz; Iron Content: 3.4 mg

These foods provide a range of iron content and can be included in a balanced diet to help meet daily iron requirements.

If that's not enough, you want to consider a liquid iron supplement, iron tablets, or other products designed to restore healthy iron levels. Let's take a look at some of those now.

Iron Supplements, Pills & Liquids

Standalone Oral Iron Supplements

Ferrous Sulfate: Commonly used to treat iron deficiency anemia, available in various strengths.

Ferrous Gluconate: A gentler form of iron with fewer gastrointestinal side effects.

Ferrous Fumarate: Often used for treating iron deficiency, known for its high iron content.

Iron Bisglycinate: A highly absorbable form of iron with minimal side effects.

Carbonyl Iron: Pure iron with fewer side effects and lower toxicity risk.

Liquid Forms of Iron: Easy-to-digest liquid form, often combined with herbs and fruit extracts.

NutriGenesis® Iron: Top form available. Cultured mineral with absorption-enhancing co-factors.

Learn more about the NutriGenesis® form of iron (and other vitamins & minerals)

Iron Supplements with Multiple Ingredients

Multivitamins Containing Iron: Comprehensive multivitamin supplements that include essential vitamins and minerals, along with iron. Look for men's and women's distinct formulas. Women require more iron than men, especially when experiencing heavy menstrual bleeding.

Pre-Workout Supplements Containing Iron: Include iron and other essential nutrients to support energy and performance. Athletes typically have higher iron requirements.

Intravenous Iron

IV iron is used to quickly treat iron deficiency anemia, especially when oral iron supplements are ineffective or cause intolerable side effects. It is also preferred for patients with malabsorption issues, chronic kidney disease, or those requiring urgent iron replenishment.

Did you know? Calcium supplements can inhibit the absorption of iron when taken together because calcium competes with iron for absorption in the intestines. To maximize the effectiveness of both supplements, it is recommended to take them at different times of the day.

These categories provide a variety of options for iron supplementation, catering to different preferences and specific health needs.

Side Effects Of Iron Pills

Iron supplements are generally safe for consumption. However, some oral iron supplements may be harsh on the digestive tract, which can lead to unpleasant symptoms like:⁽¹¹⁾

1. Nausea
2. Vomiting
3. Diarrhea
4. Heartburn
5. Abdominal pain
6. Stomach cramps
7. Metallic taste

Most side effects from taking oral iron supplements do not require medical attention and are short-lived, but if you’re experiencing things like chest or throat pain, fever, bloody stool, or double vision, contact your health care professional immediately.

Can Iron Pills Cause Constipation?

Yes, oral iron supplementation can cause constipation. In fact, constipation is one of the more common side effects of iron supplementation. Iron is a mineral that can be hard on the digestive tract and tends to cause GI-related side effects, including nausea, indigestion, gas, and bloating too.

But unlike some supplements where added ingredients can lead to constipation, iron itself is the cause.

Constipation is one of the most common side effects of taking an iron supplement because it can be hard for the body to absorb iron, regardless of whether it's from a food or iron pill.

While your GI tract is absorbing iron, it also leaves some iron behind. Any iron that isn’t absorbed can feed the harmful bacteria in the gut, which can interfere with digestive health and motility, resulting in constipation.

If you’re experiencing constipation as a side effect of iron supplementation, consider swapping your iron supplement for another form or reducing your dose slightly.

For example, 300 mg of ferrous sulfate contains about 60 mg of elemental iron per dose, whereas 300 mg of ferrous gluconate contains about 34 mg of iron per day.

For some people, ferrous gluconate has fewer side effects and is less constipating, making it a better supplement option.

Similarly, slow-release forms of iron may reduce constipation, but they don’t come without their drawbacks.

Usually, iron is absorbed in the first part of your small intestine (the duodenum), but slow-release tablets typically bypass this area before releasing iron, which means absorption can be poor.

Iron Intake Notes: Safe and Unsafe Dosages

So how much iron supplement should you really be taking? The recommended daily intake of iron varies between men and women due to differing physiological needs. For adult men aged 19 to 50 years, the recommended intake is 8 milligrams per day, which remains the same for men over 50.

Adult women aged 19 to 50 years require more iron, and may require iron supplementation, with a recommended intake of 18 milligrams per day, primarily due to menstrual blood loss. This requirement decreases to 8 milligrams per day for women over 50.

During pregnancy, women need significantly more iron, with a recommended intake of 27 milligrams per day to support the increased blood volume and fetal development. Lactating women should aim for 9 to 10 milligrams per day.

Upper tolerable Intake level to Avoid

While iron is essential for health, it is crucial not to exceed the tolerable upper intake level, which is 45 milligrams per day for adults.

Consuming too much iron can lead to several adverse effects.

In the short term, excessive iron intake can cause nausea, vomiting, diarrhea, and abdominal pain. Long-term overconsumption can result in iron accumulation in the organs, a condition known as hemochromatosis, which can cause serious health issues such as liver damage, heart problems, diabetes, and joint pain.

Iron poisoning is a severe and potentially fatal condition that typically occurs at doses above 60 milligrams per kilogram of body weight. Symptoms of acute iron toxicity include severe abdominal pain, nausea, vomiting, diarrhea (often bloody), metabolic acidosis, and liver failure.

Given the seriousness of iron poisoning, immediate medical attention is required if it is suspected. Get to a poison control center or hospital immediately in that case.

Additional tips to avoid constipation

1. Stay hydrated: Constipation can also happen because of insufficient fluid intake, so ensure you drink plenty of fluids daily to keep your bowels regular.
2. Eat more fiber: On top of proper hydration, bowel health and regularity also rely on sufficient soluble and insoluble fiber intake. If you struggle to meet your requirements for fiber (i.e., you’re not eating enough complex carbohydrates, fruits, and vegetables), consider a fiber supplement. We recommend a high-quality fiber supplement below: Performance Lab Prebiotic.
3. Take stool softener: Stool softeners work by increasing water absorption in the stool, making it softer and easier to pass, and should be taken according to the dosage instructions on the product label or as directed by a healthcare provider.

Easy to Digest Iron Supplements

NutriGenesis® Multi

NutriGenesis® nature-identical vitamin and mineral essentials for healthy biological performance.

Ingredients: 24 cultured essential vitamins and minerals complexed with cofactors for optimal potency.

Sometimes you don't need an iron supplement because a good multivitamin is enough. Performance Lab®'s ultramodern multivitamin in customized formulas for men's and women's distinct nutritional needs. Featuring advanced form NutriGenesis® lab-grown vitamins and minerals with cofactors, enzymes and probiotics that enhance their bioavailability, metabolism and utilization. Foundational support for healthy performance across all body systems, and a great way to ward off iron deficiency anemia.

Shop Performance Lab® NutriGenesis®

Pre Lab Pro®

“World’s smartest pre-workout drink": smooth energy, focus and peak performance with no jitters or crashes.

Ingredients: Red Beetroot Powder; Setria® Performance Blend; Natural Caffeine; L-Theanine; L-Tyrosine; Vitamin D3, Potassium and Iron (all as NutriGenesis®), Himalayan Pink Salt. Delicious natural berry flavor.

Iron supplements can include sport nutrition formulas like this one. Pre Lab Pro® supplies a moderate dose of sport-tuned caffeine with amino acids that balance energy with calm control. With an additional nitric oxide boost for blood flow plus natural hydration support, Pre Lab Pro® enhances intensity, motivation and mental sharpness throughout your session -- for better gym performance, muscle growth and muscle gains overall.

Shop Pre Lab Pro®

A Top Product to Combat Constipation: Prebiotic Fiber

Performance Lab Prebiotic

Filling up on fiber can help you to avoid constipation. Performance Lab® Prebiotic is a performance fiber supplement in convenient capsules.

Performance Lab Prebiotic provides advanced microflora support for digestive, immune, and metabolic health. It features Orafti® Synergy1 (Inulin-FOS from chicory root), a top prebiotic known for enhancing probiotics that relieve constipation. Each serving delivers 1.7g of fiber.

Ingredients: Each serving of 3 NutriCaps supplies two grams of Inulin-FOS (FructoOligoSaccharides) from chicory root.

What sets Performance Lab Prebiotic apart is its purity and the specific choice of inulin and FOS, which selectively feed only the healthiest probiotic bacteria like Bifidobacterium. This "targeted feeding" helps maintain a balanced gut microbiota, leading to better digestion, less bloating, and a reduction in constipation.

Benefits of Performance Lab Prebiotic Fiber:

• Normal Bowel Movement function: Increases stool frequency.
• Improved Stool Consistency: Makes stools easier to pass.
• Natural Stool Softener: Enhances stool volume and softness through gut fermentation.
• Comfortable Elimination: Supports easy and comfortable bowel movements.
• Gut Health: Strengthens gut lining, reducing leaky gut risk.

This fiber is convenient, too. It's presented in All-Natural NutriCaps: Easy-to-swallow capsules made from plant-sourced pullulan (fermented tapioca), infused with additional prebiotic fiber for extra digestive support and better absorption of oral iron supplementation.

Shop Performance Lab® Prebiotic

Conclusion

Do iron supplements cause constipation? While oral iron supplementation is crucial for addressing deficiencies and maintaining overall health, it may also come with the uncomfortable side effect of constipation.

This issue arises due to the nature of iron supplements, which can slow down the digestive process.

However, by choosing the right form of iron in dietary supplements, such as NutriGenesis® iron, ferrous gluconate or iron bisglycinate, and incorporating dietary adjustments like increasing fiber intake, staying hydrated, and engaging in regular physical activity, individuals can significantly mitigate these side effects.

Additionally, significant evidence suggests taking iron on an empty stomach can exacerbate digestive side effects. So consider taking supplements with food or in smaller doses can help reduce gastrointestinal discomfort.

As always, consulting with a healthcare provider before starting or adjusting iron supplementation is essential to ensure both effectiveness and safety. By understanding and implementing these strategies, people can benefit from iron supplementation without the added discomfort of constipation.