Chart — Endocrine
Endocrine Lab Values Chart
Quick-reference endocrine laboratory values — glucose, A1C, ketones, TSH, free T4, cortisol, ACTH, aldosterone, and insulin: normal ranges, elevated and decreased causes, and key clinical flags.
Source: ADA Standards of Medical Care; ATA Thyroid Guidelines; Endocrine Society Clinical Practice Guidelines; clinical laboratory references. Ranges reflect typical adult values — always verify with institutional norms.
Educational use only. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Lab interpretation tip: Always interpret lab values in clinical context. A normal TSH rules out most primary thyroid disease; an elevated A1C alone does not diagnose DKA; and cortisol must be interpreted with ACTH together to localize adrenal pathology.
Glucose & Diabetes
| Lab Test | Normal Range | Elevated Causes | Decreased Causes |
|---|---|---|---|
| Fasting glucose | 70–99 mg/dL | DM (≥126), prediabetes (100–125), steroid use, Cushing, pancreatitis, acromegaly, stress hyperglycemia | Insulin excess, prolonged fasting, Addison disease, insulinoma, liver failure |
| Random glucose | 70–139 mg/dL (post-meal) | Diabetes, DKA, HHS — ≥200 + symptoms = DM diagnosis | Hypoglycemia — <70 requires treatment |
| ★ Critical: <40 or >500 notify immediately | |||
| A1C (HbA1c) | <5.7% | Diabetes (≥6.5%), prediabetes (5.7–6.4%), chronic hyperglycemia | Hemolytic anemia, blood transfusion (falsely low due to shorter RBC lifespan) |
| ★ Each 1% ≈ 28–30 mg/dL average glucose | |||
| Serum ketones / urine ketones | Negative to trace | DKA (large ketones), starvation ketosis, alcoholic ketoacidosis, SGLT2 inhibitor use | Not clinically relevant when decreased |
| ★ Large ketones + acidosis = DKA until proven otherwise | |||
| C-peptide | 0.5–2.0 ng/mL (fasting) | Insulinoma, sulfonylurea use, Type 2 DM with residual beta cell function | Type 1 DM (beta cell destruction), factitious hypoglycemia from injected insulin |
| ★ Low C-peptide + hypoglycemia = likely exogenous insulin or T1DM | |||
Thyroid
| Lab Test | Normal Range | Elevated Causes | Decreased Causes |
|---|---|---|---|
| TSH | 0.4–4.0 mIU/L | Primary hypothyroidism (pituitary releases more TSH to stimulate failing thyroid); TSH >10 = overt hypothyroidism | Hyperthyroidism (excess thyroid hormone suppresses TSH); secondary hypothyroidism (pituitary failure) |
| ★ Best first-line thyroid screening test | |||
| Free T4 | 0.8–1.8 ng/dL | Hyperthyroidism, Graves disease, thyroid storm, exogenous T4 excess | Hypothyroidism, euthyroid sick syndrome, severe illness |
| ★ Use with TSH for full picture: High T4 + Low TSH = hyperthyroid; Low T4 + High TSH = primary hypothyroid | |||
| Free T3 | 2.3–4.2 pg/mL | Hyperthyroidism, T3 thyrotoxicosis | Hypothyroidism, severe nonthyroidal illness |
| ★ Active hormone; useful in suspected thyroid storm | |||
Adrenal
| Lab Test | Normal Range | Elevated Causes | Decreased Causes |
|---|---|---|---|
| Cortisol (AM serum) | 6–23 mcg/dL (AM) | Cushing syndrome/disease, exogenous steroids, severe stress, sepsis, obesity | Adrenal insufficiency (Addison disease = primary; pituitary failure = secondary) |
| ★ AM cortisol <3 mcg/dL = highly suspicious for adrenal insufficiency | |||
| ACTH | 7–50 pg/mL (AM) | Primary adrenal insufficiency (Addison — adrenal fails, ACTH rises); Cushing DISEASE (pituitary adenoma) | Secondary/tertiary adrenal insufficiency; Cushing SYNDROME (exogenous steroids or adrenal tumor suppresses ACTH) |
| ★ Key: High ACTH + Low cortisol = Addison. Low ACTH + High cortisol = adrenal tumor or exogenous steroid. | |||
| Aldosterone | 3–16 ng/dL (supine) | Primary hyperaldosteronism (Conn syndrome); secondary hyperaldosteronism (HF, cirrhosis, RAS) | Adrenal insufficiency, Addison disease, hypoaldosteronism, ACE inhibitor/ARB use |
| ★ Hyperaldosteronism: HTN + hypokalemia (classic triad) | |||
Pancreatic / Other
| Lab Test | Normal Range | Elevated Causes | Decreased Causes |
|---|---|---|---|
| Insulin (fasting) | 2–25 mcIU/mL | Insulin resistance (Type 2 DM, obesity, PCOS), insulinoma, exogenous insulin injection | Type 1 DM (absolute deficiency); late-stage Type 2 DM |
| ★ High fasting insulin during hypoglycemia = insulinoma or sulfonylurea | |||
| Anion gap | 8–12 mEq/L | DKA, lactic acidosis, uremia, toxic ingestions (MUDPILES mnemonic) | Rarely clinically significant (hypoalbuminemia, multiple myeloma) |
| ★ DKA: anion gap >12 (gap acidosis). Gap closure = DKA resolution, NOT glucose normalization alone. | |||
Related Resources
Standards & sources
Fact-checked Jun 20, 2026This page is written to align with ADA Standards of Medical Care; ATA Thyroid Guidelines; Endocrine Society Clinical Practice Guidelines. It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →