Feeling tired, foggy, or cranky for weeks? A single nutrient gap can be the cause. I’ll keep this practical: what to watch for, quick tests to ask your doctor about, and safe steps to fix shortages without guessing.
Iron: persistent tiredness, shortness of breath with small effort, pale skin, and cravings for ice or dirt. A ferritin test and CBC tell the story.
Vitamin B12: numb hands or feet, memory slips, and low mood. Long-term use of acid blockers like lansoprazole (Prevacid) can lower B12 absorption. Ask for B12 and methylmalonic acid (MMA) tests.
Vitamin D: low energy, bone aches, weak muscles and more colds than usual. A 25(OH)D blood test shows your levels.
Magnesium: muscle cramps, restless sleep, and anxiety. Low magnesium shows on specific labs but often gets missed.
Protein and calorie gaps: weight loss, slow healing, and low strength. Simple dietary review catches this fast.
Some drugs make you lose or absorb less of certain nutrients. Proton pump inhibitors and metformin, for example, can reduce B12 absorption over time. Statins may lower CoQ10, which can feel like muscle weakness. Antibiotics can alter gut bacteria and affect vitamin production.
Diet matters: strict vegan or very low-calorie diets often miss B12, iron, and sometimes vitamin D. Gut problems like celiac disease, Crohn’s, or recent bowel surgery reduce absorption. Heavy periods or frequent blood loss drain iron stores fast.
Testing is cheap compared with months of low energy. Basic starter panel: CBC with ferritin, B12 (±MMA), 25(OH)D, and basic metabolic panel. Your doctor can add nutrients based on symptoms.
Treat smart: start with food. Spinach, red meat, and lentils for iron (eat with vitamin C to help absorption). Fatty fish, eggs, and sunlight for vitamin D. Fortified foods or B12 shots if you’re vegan or malabsorbent.
Supplements help but use them wisely. High-dose iron can upset your stomach and should be guided by a lab result. Vitamin D doses vary; a short blood test after 8–12 weeks shows if the dose worked. B12 injections bypass gut issues and bring fast relief for severe deficiency.
Watch for interactions: calcium or iron can interfere with levothyroxine and certain antibiotics. Tell your pharmacist about every drug and supplement you take. If you order meds online, choose reputable pharmacies and check labels.
When to see a doctor now: sudden weakness, breathlessness, chest pain, severe numbness, or changes in vision. For slow issues like fatigue or hair loss, get the simple tests above before starting random supplements.
Want a quick checklist? 1) Note top symptoms, 2) get CBC, ferritin, B12, 25(OH)D, 3) review meds with a pro, 4) fix with food first, 5) use targeted supplements as recommended. Follow-up labs after treatment confirm you’re back on track.
Explore related guides on our site to learn specifics—iron dosing, safe B12 injections, and how long to take vitamin D. Small fixes often make the biggest difference in how you feel every day.
