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Common Deficiencies

Nutrients often evaluated by labs or dietary context, where supplementation depends on levels, diet, and life stage.

Evidence guide

This guide gathers nutrients usually checked through lab tests or dietary context, where supplementation depends on levels, diet, and life stage. It does not promise outcomes: it orders the options by evidence, safety, and when a deficiency should be confirmed with a professional.

How to interpret this category

  • Vitamin D may be associated with bone health, immunity, and muscle function; deficiency is common and is assessed with a 25-hydroxyvitamin D test.
  • Iron should be guided by labs (ferritin and hemoglobin); supplementing without confirming can be unnecessary or counterproductive.
  • Vitamin B12 and folate are especially relevant for vegan or vegetarian diets, malabsorption, and early pregnancy; confirming them with labs is advisable.

Priority comparisons

Vitamin D and deficiencyA common deficiency assessed with a 25-OH vitamin D test. It may be associated with bone health, immunity, and muscle function; a prudent dose depends on the level and context.Open the vitamin D guideIron guided by labsSupplementation is decided with ferritin and hemoglobin, not isolated symptoms. Review dose, digestive tolerance, and interactions with a professional.Open the iron guideVitamin B12 for diets and malabsorptionRelevant for vegan or vegetarian diets and malabsorption. It is confirmed with labs and adjusted by cause and levels.Open the vitamin B12 guide

Recommended next reading

Folate and pregnancyImportant for cell division; its use matters before and during early pregnancy, with professional follow-up.Review folateZinc by diet and contextA mineral for immunity, skin, and reproductive function; supplementation depends on diet and clinical context.Review zincEnergy and fatigueWhen tiredness is the main concern, it helps to rule out deficiencies (iron, B12, vitamin D) with labs before choosing supplements.Open energy supplements

Compared supplements

A

Vitamin D

Common deficiency in many populations. Key for bone health, immunity, and muscle function.

A

Iron

Essential for oxygen transport. Supplementation should be guided by labs, especially ferritin and hemoglobin.

A

Vitamin B12

Critical for the nervous system and red blood cells. Especially relevant in vegan or vegetarian diets and malabsorption.

A

Folate

Important for cell division and pregnancy. Use is key before and during early gestation.

B

Zinc

Important mineral for immunity, skin, and reproductive function. Supplementation depends on diet and clinical context.

Supplement guides

Vitamin DIronVitamin B12FolateZinc

Frequently asked questions

How do I know if I have a deficiency?

Deficiencies are confirmed with lab tests (for example 25-OH vitamin D, ferritin, hemoglobin, B12, and folate), not symptoms alone. A professional interprets the results based on your diet, life stage, and history.

Which lab tests are worth requesting?

It depends on the case, but vitamin D (25-OH), an iron panel (ferritin and hemoglobin), vitamin B12, and folate are commonly assessed. Discuss with your professional which ones apply to you.

Can I supplement without lab tests?

It is not ideal, especially with iron: supplementing without confirming levels can be unnecessary or counterproductive. The prudent path is to assess with labs and consult a professional.

When should I talk to a professional?

When there are persistent symptoms, pregnancy or trying to conceive, restrictive diets, malabsorption, or medication use. In those cases clinical assessment takes priority over self-supplementation.