Can Being Vegan Cause Fatigue? Understanding the Causes and Cures

November 16, 2025 •

4 min read

Research indicates that vegans and vegetarians are at a higher risk of certain nutrient deficiencies, including B12 and iron, compared to omnivores. This fact leads many to question: can being vegan cause fatigue if the diet is not thoughtfully planned and managed?

Quick Summary

A vegan diet can sometimes result in fatigue due to insufficient calories or specific nutrient deficiencies like B12 and iron. Proper meal planning, supplementation, and focusing on whole foods can help prevent low energy.

Key Points

B12 Supplementation is Crucial: Since B12 is not naturally present in plant foods, a reliable supplement or fortified food source is essential for vegans to prevent deficiency and fatigue.
Check Your Calories: Plant-based whole foods are often less calorie-dense than animal products. Not eating enough overall calories is a common cause of fatigue for new vegans.
Boost Iron Absorption: Vegans are at a higher risk of iron deficiency. Pairing iron-rich plant foods with Vitamin C helps maximize absorption of non-heme iron.
Focus on Whole Foods: Relying on processed vegan junk food can lead to nutrient deficiencies and energy crashes. Prioritizing whole foods like legumes, grains, and nuts provides sustained energy.
Balanced Meals are Key: Combining carbohydrates with protein and fat helps stabilize blood sugar, preventing the energy dips that can follow carb-heavy meals.
Consider All Lifestyle Factors: Poor sleep, high stress, and dehydration can also contribute to fatigue, even with a balanced diet. Addressing these is important for overall energy.

Understanding the Root Causes of Vegan Fatigue

Feeling a slump in energy after switching to a vegan diet is not uncommon, but it's important to understand that the diet itself is rarely the problem. In most cases, fatigue stems from poor dietary planning or a lack of awareness about key nutrients. The transition from a diet with calorie-dense animal products to one of lower-calorie plant foods often requires a significant adjustment in portion sizes and food choices to ensure adequate energy intake. A well-planned vegan diet can provide all the necessary nutrients for optimal energy, but it requires paying careful attention to sources of calories, vitamins, and minerals that are typically abundant in animal products.

Key Nutritional Deficiencies Linked to Fatigue

Several nutrients are vital for energy production and are less bioavailable or absent in plant foods. Being mindful of these can help prevent energy dips.

Vitamin B12: This vitamin is crucial for red blood cell formation and nervous system function. Since B12 is found almost exclusively in animal products, vegans must supplement or consume fortified foods to avoid a deficiency, which can cause significant fatigue. Fortified sources include nutritional yeast, certain plant milks, and some breakfast cereals.
Iron: Iron is necessary for producing hemoglobin, which carries oxygen throughout the body. Plant-based (non-heme) iron is not absorbed as efficiently as heme iron from animal sources. Vegans, particularly women of child-bearing age, are at greater risk of iron deficiency. Combining iron-rich plant foods with Vitamin C dramatically increases absorption.
Protein: While most plant foods contain protein, ensuring sufficient and varied intake is essential. Protein is vital for building and repairing tissues, and it also helps stabilize blood sugar, preventing energy crashes that can occur after high-carb meals. Legumes, tofu, nuts, seeds, and whole grains are excellent sources.
Omega-3 Fatty Acids: DHA and EPA are essential for brain health and cell function. Primarily found in fatty fish, vegans need to consume ALA from sources like flaxseeds, walnuts, and chia seeds, or consider an algae-based supplement, as the body’s conversion rate of ALA to DHA/EPA is low.

The Crucial Role of Calorie Density

One of the most common reasons for fatigue among new vegans is simply not eating enough calories. Plant-based whole foods are often less calorie-dense and higher in fiber than animal products, meaning you may feel full before you have consumed enough energy for your body's needs. To counteract this, it's vital to incorporate more calorie-dense whole foods into your diet. This includes nuts, seeds, nut butters, avocados, and whole grains. Smoothies are also a great way to pack in extra calories with nut butters, seeds, and oats. Tracking your intake for a week can help identify if low energy is due to insufficient caloric intake.

Lifestyle Factors Impacting Energy Levels

Beyond nutrition, other lifestyle elements can contribute to fatigue, regardless of diet. It's crucial to address these for holistic well-being.

Sleep: Chronic fatigue can be a direct result of inadequate or poor-quality sleep. Adults typically need 7-9 hours per night.
Stress: High-stress levels can deplete energy reserves. Techniques like meditation, yoga, or spending time in nature can help manage stress.
Hydration: Even mild dehydration can cause fatigue. Ensuring you drink enough water throughout the day is a simple yet effective way to maintain energy levels.
Processed Foods: A diet heavy in processed vegan junk food, which often lacks fiber and essential nutrients, can cause energy crashes due to blood sugar spikes and drops. Focusing on whole foods is key.

Nutrient Absorption Comparison Table


Nutrient	Omnivore Sources (Heme)	Vegan Sources (Non-Heme)	Absorption Tips for Vegans
Iron	Red meat, poultry, fish	Lentils, beans, tofu, spinach	Pair with Vitamin C; avoid coffee/tea with meals.
Vitamin B12	Meat, dairy, eggs	Fortified cereals, nutritional yeast	Mandatory Supplementation is highly recommended.
Omega-3s	Fatty fish	Flaxseeds, chia seeds, walnuts	Consider an algae-based DHA supplement for direct conversion.
Calcium	Dairy products	Fortified plant milks, tofu, leafy greens	Ensure adequate intake from varied sources.
Zinc	Meat, shellfish	Tofu, legumes, pumpkin seeds	Soaking/sprouting nuts and seeds improves absorption.

Strategizing for Sustained Vegan Energy

Meal Planning: Create a weekly meal plan to ensure you are consuming a variety of nutrient-dense foods. A balanced diet should include a mix of whole grains, legumes, vegetables, fruits, nuts, and seeds.
Smart Supplementation: A B12 supplement is non-negotiable for vegans. Consider blood tests to check levels of iron, B12, and Vitamin D, and supplement as needed under a doctor's guidance.
Enhance Absorption: Maximize nutrient absorption by pairing iron-rich foods with sources of Vitamin C and avoiding tea or coffee around meal times.
Listen to Your Body: Pay attention to how different foods affect your energy levels. If you feel sluggish after a meal, it may be a sign of a blood sugar crash, and you may need more protein and fats to balance the carbs.

For more detailed information on specific deficiencies and optimal vegan diet planning, consult resources from registered dietitians or reputable organizations like Vegan Health, which provides expert-reviewed nutritional advice for plant-based diets. Vegan Health

Conclusion: Fatigue is a Symptom, Not a Vegan Predicament

Feeling fatigued on a vegan diet is not an inherent side effect of eating plant-based foods, but rather a sign that your nutritional needs may not be fully met. By paying close attention to your intake of calories and key nutrients like B12 and iron, and managing lifestyle factors like sleep and stress, you can easily overcome fatigue. A thoughtful and well-planned vegan diet is fully capable of providing all the necessary fuel for a vibrant, energetic life. If symptoms persist after adjusting your diet, it's always best to consult a healthcare professional to rule out other medical issues.

Frequently Asked Questions

It is not unusual to feel tired initially, as your body adjusts to the different calorie density and nutrient profile of a plant-based diet. This often resolves with improved meal planning and strategic nutrient intake, especially B12 and iron.

As B12 is not naturally found in plant foods, the most reliable way is through consistent supplementation or by regularly consuming foods fortified with B12, such as nutritional yeast, certain plant milks, and fortified cereals.

Plant-based, or non-heme, iron is not absorbed as efficiently as the heme iron found in animal products. Vegans, especially menstruating women, are at a higher risk of deficiency if not careful about optimizing iron intake and absorption.

Yes. Plant foods tend to be lower in calories than animal products. It is a common mistake for new vegans to eat smaller portions, leading to an overall calorie deficit and resulting fatigue.

Common symptoms can include fatigue, weakness, dizziness, headaches, and brain fog. Specifically, a B12 deficiency can cause neurological issues, while iron deficiency can lead to anemia.

It's important to also monitor your intake of Omega-3 fatty acids, protein, Vitamin D, Zinc, and Calcium. While most can be obtained from plants, absorption and conversion can vary.

If your fatigue persists despite improving your dietary planning, increasing calorie intake, and ensuring proper supplementation, you should consult a doctor. They can run blood tests to identify underlying deficiencies or other health issues.