NLM Classification 2025 Summer Edition Now Available

The NLM Classification was updated on September 2, 2025. The National Library of Medicine (NLM) is committed to regularly updating and revising the NLM Classification based on advancements in science and current events. Each year NLM selects portions of the classification schedules for systematic review and revision. This edition marks the completion of the systematic review of all 36 schedules of the NLM Classification which began in 2007.

The major focus of the 2025 summer edition was the systematic review of the following schedules: WK Endocrine System and WQ Obstetrics. Pregnancy. In addition to the systematic reviews of the WK and WQ schedules, other minor additions and changes were made.

Summary Statistics for the 2025 Summer Edition

• 2 schedule headers modified.
• 61 class numbers added.
• 2 range headers added.
• 76 class number captions or notes modified.
• 5 range headers modified.
• 21 class numbers canceled.
• 3 range headers deleted.
• 61 index main headings added.
• 219 index entries modified.
• 63 index headings deleted.

Systematic Reviews for the 2025 Summer Edition

Highlights from WK Endocrine System

• 24 NEW WK CLASS NUMBERS.

  New Class Number	Caption
  WK 90	[Endocrine system] General works
  WK 105	Androgens. Androgen antagonists
  WK 110	Estrogens. Estrogen antagonists
  WK 112	Estrogen replacement therapy
  WK 220	Thyroid diseases (General or not elsewhere classified)
  WK 517	Growth hormone
  WK 812	Diabetes mellitus, Type I
  WK 835.5	[Diabetes complications] Specific complications, A-Z
  WK 835.5.A5	Diabetic angiopathies
  WK 835.5.C2	Diabetic cardiomyopathies
  WK 835.5.C6	Diabetic coma
  WK 835.5.D2	Diabesity
  WK 835.5.F5	Diabetic foot
  WK 835.5.K4	Diabetic ketoacidosis
  WK 835.5.N3	Diabetic nephropathies
  WK 835.5.N6	Diabetic neuropathies
  WK 835.5.R3	Diabetic retinopathy
  WK 925	Corpus luteum hormones
  WK 930	Gonadal steroid hormones
  WK 932	Female gonadal steroid hormones
  WK 933	Male gonadal steroid hormones
  WK 935	Estradiol congeners
  WK 940	Progesterone congeners
  WK 945	Testicular hormones. Testosterone congeners

  
  
  
• 3 NEW CLASS NUMBERS IN OTHER SCHEDULES RELATED TO WK SYSTEMATIC REVIEW.

  New Class Number	Caption
  QV 176	Tocolytic agents
  QV 205	Hypoglycemic agents
  WH 710	Lymphoid tissue

• 14 CANCELED WK CLASS NUMBERS

  Canceled Class Number	Former Caption	New Instructions for Classification
  WK 180	Renal hormones	Classify works on renal hormones in WJ 301
  WK 201	[Thyroid gland] Anatomy. Histology. Embryology. Abnormalities	Classify works on the thyroid gland in WK 200
  WK 267	[Thyroid diseases] Medical therapy	Classify works on hyperthyroidism in WK 265
  WK 400	Thymus gland	Classify works on the thymus gland in WH 710
  WK 501	[Pituitary gland] Anatomy. Histology. Embryology	Classify works on the pituitary gland in WK 500
  WK 701	[Adrenal glands] Anatomy. Histology. Embryology	Classify works on the adrenal glands in WK 700
  WK 702	[Adrenal glands] Physiology. Biochemistry	Classify works on the physiology of the adrenal glands in WK 700
  WK 801	[Islets of Langerhans] Anatomy. Histology. Embryology	Classify works on the Islets of Langerhans and pancreatic hormones in WK 800
  WK 802	[Islets of Langerhans] Physiology. Biochemistry	Classify works on the Islets of Langerhans and pancreatic hormones in WK 800
  WK 825	Other hypoglycemic agents	Classify works on other hypoglycemic agents in QV 205
  WK 830	Diabetic ketoacidosis. Diabetic coma	Classify works on diabetic coma in WK 835.5.C6; diabetic ketoacidosis in WK 835.5.K4
  WK 840	Diabetes as a complication in other conditions	Classify works on the co-occurrence of diabetes and other conditions in WK 835
  WK 870	Glycosurias	Classify works on glycosuria in QU 260.5.G6
  WK 920	Placental hormones	Classify works on placental hormones in WQ 212

• 37 MODIFED WK CLASS NUMBERS.
• 7 MODIFED CLASS NUMBER IN OTHER SCHEDULES RELATED TO WK SYSTEMATIC REVIEW.

Highlights from WQ Obstetrics. Pregnancy

• Pregnancy was added to the WQ schedule header.
• 8 NEW WQ CLASS NUMBERS.
  

  New Class Number	Caption
  WQ 180	Perinatal care
  WQ 201	Pregnancy in Adolescence (General)
  WQ 208.2	Artificial insemination
  WQ 208.4	Fertilization in vitro
  WQ 209.5	Fetal monitoring
  WQ 254	High-Risk pregnancy
  WQ 445	Induced abortion
  WQ 507	Postpartum depression

• 6 NEW CLASS NUMBERS IN OTHER SCHEDULES RELATED TO WQ SYSTEMATIC REVIEW.

  New Class Number	Caption
  WA 548	Reproductive health services (Table-G)
  WA 548.1	[Reproductive health services] General coverage (Not Table-G)
  WP 20.5	Reproductive medicine as a profession. Ethics. Peer review
  WP 50	Reproductive health. Reproductive history (Table-G)
  WP 50.1	[Reproductive health. Reproductive history] General coverage (Not Table-G)
  WP 620	Reproductive techniques (General or not elsewhere classified)

• 2 CANCELED WQ CLASS NUMBERS.

  Deleted Class Number	Former Caption	New Instructions for Classification
  WQ 90	Reproductive health surveys (Table-G)	Classify works on reproductive health surveys in WP 50
  WQ 90.1	[Reproductive health surveys] General coverage (Not Table-G)	Classify works on reproductive health surveys without geographic coverage in WP 50.1

• 19 MODIFED WQ CLASS NUMBERS.
• 9 MODIFED CLASS NUMBER IN OTHER SCHEDULES RELATED TO WQ SYSTEMATIC REVIEW.

Next Edition

The 2026 winter edition will be published in late January 2026. It will encompass the additions and changes from the 2026 MeSH (Medical Subject Headings) vocabulary as evaluated for inclusion in the Classification index. All main index headings will be linked to the 2026 vocabulary in the MeSH Browser at that time.

To learn more about the NLM Classification see the NLM Policy on Classification.