Can an intrauterine device (IUD) cause anemia?

Can an IUD Cause Anemia?

Yes, copper IUDs can cause or worsen anemia through increased menstrual blood loss, while levonorgestrel IUDs actually improve anemia by reducing menstrual bleeding.

Type-Specific Effects on Anemia

Copper IUDs (Cu-IUD)

• Copper IUDs increase menstrual blood loss, which can precipitate or aggravate iron deficiency anemia 1
• Studies show that Cu-IUD users experience statistically significant decreases in hemoglobin levels during 12 months of follow-up, though the magnitude is typically small and may not be clinically significant in women without pre-existing anemia 1
• Serum ferritin levels decline significantly with copper IUD use, indicating depletion of iron stores even when hemoglobin remains stable 2, 3
• Research demonstrates that 55-70% of long-term copper IUD users develop low ferritin levels (below 11 ng/ml), and 22-26% develop subnormal hematocrit 3, 4
• The Lippes Loop causes the greatest increase in menstrual blood loss, sustained throughout 24 months of use 3

Levonorgestrel IUDs (LNG-IUD)

• The LNG-IUD improves anemia markers rather than causing anemia 1
• Women with iron-deficiency anemia can use the LNG-IUD without restriction (U.S. MEC Category 1) 1
• The LNG-IUD is beneficial for treating heavy menstrual bleeding (menorrhagia), with evidence showing no increase in adverse effects 1
• Laboratory improvements include: significant increases in hemoglobin, hematocrit, serum iron, and ferritin levels in women with heavy menstrual bleeding 5
• Only 2% of long-term LNG-IUD users develop subnormal hematocrit, compared to 22-26% with copper IUDs 4
• The LNG-IUD reduces menstrual blood loss by 40-50% and increases serum ferritin 3

Clinical Management Algorithm

For Women Considering Copper IUDs:

• Pre-insertion screening for anemia is not necessary according to U.S. guidelines, as the changes in hemoglobin are generally not clinically significant 1
• However, women with pre-existing iron deficiency anemia can still use copper IUDs (U.S. MEC Category 2 - generally can use) 1
• Consider measuring serum ferritin in long-term copper IUD users to identify iron depletion before clinical anemia develops 6

For Women with Heavy Menstrual Bleeding or Anemia:

• The LNG-IUD is the preferred choice as it treats both the bleeding and improves anemia markers 7, 5
• The LNG-IUD is particularly useful for women with severe thrombocytopenia who have menorrhagia 1
• Expect improvement in hemoglobin, hematocrit, serum iron, and ferritin within one year of placement 5

Important Caveats

• Women in developing countries or with marginal iron stores are at higher risk for clinically significant anemia with copper IUDs 3
• The risk of anemia is particularly concerning with long-term copper IUD use (beyond 12 months) 2
• Self-selection bias may underestimate the true risk, as women who develop significant bleeding often discontinue IUD use 6
• Increased dietary iron absorption may partially compensate for increased menstrual losses in some women 6