Nutritional deficiencies: how to spot, test, and fix them

Want to feel less tired, have stronger nails, and stop brain fog? Low nutrients can be the hidden cause. Even people who eat a lot can miss key vitamins and minerals. This page helps you recognize common deficiencies, get the right tests, and take simple steps to improve your levels.

Common deficiencies and what they look like

Here are the usual suspects and the signs to watch for:

• Iron: fatigue, shortness of breath with activity, pale skin, restless legs, cold hands.
• Vitamin B12: numbness or tingling in hands/feet, memory issues, mood changes, extreme tiredness.
• Vitamin D: bone or muscle pain, feeling low on energy, slower healing, more colds.
• Folate (B9): weakness, mouth sores, trouble concentrating; important in pregnancy.
• Magnesium & Calcium: muscle cramps, twitching, bone weakness, trouble sleeping.

Symptoms can overlap, so one sign doesn’t prove a deficiency. But patterns—like fatigue plus brittle nails and heavy periods—point toward specific issues like iron loss.

How to test and what to ask your doctor

Blood tests are the only reliable way to know for sure. Ask your doctor for targeted tests based on symptoms. Useful tests include a complete blood count (CBC), ferritin for iron stores, serum B12, 25‑hydroxy vitamin D, folate, and basic metabolic panel for calcium and magnesium. If you take medications like metformin, proton pump inhibitors, or have digestive disease, tell your clinician—these raise risk for poor absorption.

If you can’t see a doctor right away, many clinics and labs offer direct blood tests you can order. Still, a clinician’s help matters when interpreting results and deciding on treatment.

Fixing a deficiency usually involves three steps: food first, then targeted supplements if needed, and follow-up testing.

Food sources work well for many people. Iron-rich foods: red meat, poultry, lentils, spinach, and fortified cereals (eat with vitamin C to boost absorption). B12: animal products, fortified plant milks, and nutritional yeast. Vitamin D: fatty fish, fortified dairy or plant milks, and safe sun exposure. Folate: leafy greens, beans, and fortified grains. Magnesium: nuts, seeds, whole grains, and leafy greens.

Supplements are helpful when diet alone won't close the gap—like with marked deficiency, poor absorption, or specific health conditions. Use forms that absorb well (for example, methylcobalamin for B12 for some people) and follow medical advice on dose and duration. After a period of treatment, recheck levels to make sure you're improving and avoid overtreatment.

If you have sudden severe symptoms—fast heartbeat, fainting, severe numbness, or bone pain—seek medical care quickly. For most people, small consistent changes in diet plus one check-up will prevent small nutrient gaps from turning into bigger problems.

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