Plant-based eating was supposed to energize me—instead, I could barely function until I finally figured out what I was doing wrong

The morning I couldn’t lift my coffee mug without my hands trembling, I knew something was seriously wrong. Three months into my plant-based journey, I was supposed to be glowing with vibrant health. Instead, I was googling “why am I so tired on a vegan diet” while lying on my bathroom floor, too exhausted to stand up after my shower.

Everyone had promised me boundless energy. Instagram influencers with their green smoothies and perfect skin. My yoga instructor who credited her plant-based diet for her ability to teach six classes a day. Even my best friend Sarah, who’d gone vegan two years earlier and wouldn’t shut up about how amazing she felt. So why was I falling apart?

At 34, I’d decided to go plant-based for all the right reasons. My cholesterol was creeping up, I wanted to reduce my environmental impact, and honestly, after watching that documentary everyone talks about, I couldn’t look at meat the same way. I dove in headfirst, clearing out my fridge, stocking up on quinoa and chickpeas, and downloading every vegan recipe app I could find.

The first week was actually great. I felt lighter, less sluggish after meals. I was proud of myself for making such a positive change. But by week three, the cracks started showing. I’d wake up feeling like I’d been hit by a truck. My afternoon brain fog was so intense that I’d stare at my computer screen, unable to remember what I was working on. My normally thick hair was coming out in clumps in the shower.

“Maybe it’s just detox,” I told myself, echoing what I’d read in countless blog posts. “Your body is adjusting.”

But by month two, the “detox” excuse was wearing thin. I was bloated constantly, my stomach distended like I was five months pregnant. My period, usually reliable as clockwork, had gone MIA. The stairs to my apartment that I used to bound up two at a time now required a rest break halfway.

My husband tried to be supportive, but I could see the concern in his eyes when I’d push my dinner around my plate, too nauseous to eat the Buddha bowl I’d spent an hour preparing. “Maybe you should see a doctor,” he suggested gently one night as I lay on the couch with a heating pad on my stomach.

Pride kept me going for another month. I was determined to make this work. I increased my portions, thinking maybe I wasn’t eating enough. I added more nuts and avocados for healthy fats. I made sure every meal had protein—tofu, tempeh, beans, lentils. I was doing everything right, wasn’t I?

The breaking point came during a work presentation. Standing in front of twenty colleagues, I suddenly couldn’t remember the next slide. My mind went completely blank. The room started spinning, and I had to grip the podium to stay upright. “I’m sorry, I just need a moment,” I mumbled, rushing to the bathroom where I sat with my head between my knees, fighting off waves of dizziness.

That night, I finally broke down and called Sarah. “I don’t understand what I’m doing wrong,” I sobbed into the phone. “I’m eating so healthy, but I feel like I’m dying.”

“Wait, what supplements are you taking?” she asked.

“Supplements? I mean, I have a multivitamin somewhere…”

The silence on the other end of the line was deafening.

“Oh honey,” she finally said. “We need to talk.”

What followed was the conversation that changed everything. Sarah explained what she wished someone had told her when she started: being plant-based wasn’t just about removing animal products and calling it a day. It required strategic supplementation that no one really talks about because it doesn’t fit the “plants have everything you need” narrative.

“B12,” she said firmly. “You absolutely need B12. It’s not naturally found in plant foods, and deficiency can cause exactly what you’re experiencing—fatigue, brain fog, weakness.” She rattled off more: vitamin D3, iron with vitamin C for absorption, omega-3s from algae, zinc. “And get your blood work done. You might need more than the standard doses.”

I felt both relieved and frustrated. Why wasn’t this information front and center in every article about going plant-based? Why did I have to nearly collapse at work to learn this?

The next day, I made two appointments—one with my doctor for comprehensive blood work, and another with a nutritionist who specialized in plant-based diets. The blood work revealed what I’d feared: I was severely deficient in B12, vitamin D, and iron. My ferritin levels were so low that my doctor was shocked I was still functioning.

The nutritionist was equally enlightening. She looked at my food diary and immediately spotted issues beyond just supplements. “You’re not eating enough calories,” she said bluntly. “Plant foods are less calorie-dense, so you need larger portions. And where’s your iodine source? Your zinc? Are you combining foods properly for protein completion?”

I left her office with a meal plan, a supplement protocol, and a bruised ego. How had I been so naive?

The transformation wasn’t immediate, but it was dramatic. Within two weeks of starting B12 injections and a proper supplement routine, the brain fog lifted. By week three, I had energy to exercise again. After a month, my period returned, my hair stopped falling out, and I could make it through the day without needing a nap.

But supplements were only part of the puzzle. I learned to eat more—way more. Where I used to have a small bowl of oatmeal for breakfast, I now loaded it with nuts, seeds, nut butter, and fruit. I discovered nutritional yeast (hello, B vitamins!), incorporated sea vegetables for iodine, and started treating meal planning like a part-time job.

Six months later, I finally felt like those glowing influencers I’d envied. My energy was consistent, my blood work was perfect, and yes, my skin did look pretty great. But I was angry too. Angry that the mainstream plant-based movement glosses over these crucial details. Angry that I’d had to suffer to learn what should be basic information.

Now, when friends tell me they’re thinking about going plant-based, I don’t just congratulate them. I sit them down and have the conversation Sarah had with me. I tell them about B12, about the importance of supplements, about eating enough calories, about getting regular blood work. I share the resources I wish I’d had from the start.

Being plant-based has been one of the best decisions I’ve made, but it almost broke me because I didn’t have the full picture. The truth is, you can absolutely thrive on a plant-based diet, but pretending it doesn’t require careful planning and supplementation is dangerous and irresponsible.

So if you’re reading this while googling “why do I feel terrible on a vegan diet” from your bathroom floor, know that you’re not alone, you’re not failing, and it’s not your fault. You just need the information that, for some reason, the plant-based community seems reluctant to shout from the rooftops: supplements aren’t optional—they’re essential. And there’s nothing unnatural or wrong about that. What’s wrong is pretending otherwise.