Dairy cattle veterinarians rely on detailed clinical examination of ill animals to identify specific diseases. However, even the most experienced clinicians occasionally may not arrive at a definitive diagnostic after clinical examination. Assessment of blood parameters (e.g., blood cells, hepatic enzymes) is a common practice performed by veterinarians to aid in disease diagnosis and determine best treatment approaches. The objective of this study was to provide reference blood parameters of dairy cows that experienced common health disorders. A total of 399 health records from a veterinary practice that provided veterinary care to 5 dairy farms were analyzed. Health events were grouped in 9 categories: (1) DIG (digestive diseases; n = 134); (2) UTD (uterine diseases; n = 101); (3) DC (down cow; n = 73), (4) MAST (mastitis; n = 55); 5) PNEU (pneumonia; n = 16); (6) LAME (lameness; n = 15), (7) INJ (injury; n = 13), (8) OTHER (n = 31) and (9) UNKNOWN (no diagnosis; n = 59). The data were analyzed using the MEANS and MIXED procedures of SAS. After clinical examination, 79.20%, 17.04% and 3.76% of ill animals were diagnosed with 1, 2, or 3+ health events, respectively. DIG health events were the most common (24.12%) reason that dairy farmers called their veterinarian, followed by DC (17.14%) and UTD (14.92%). Interestingly, veterinarians did not arrive at a definitive diagnosis in 14.78% of the clinical cases. Regardless, cows diagnosed with only 1 health event had higher (P = 0.02) concentration of neutrophils (3.40 ± 1.07 cells × 10⁶/mL) compared with cows diagnosed with 3+ health events (1.28 ± 1.42 cells × 10⁶/mL). UNKNOWN group cows had increased microhematocrit compared with normal values. DIG cows had increased concentrations of aspartate transaminase (AST), creatinine kinase (CK), and total bilirubin (TB) compared with normal values. Similarly, UTD cows had elevated concentration of AST and CK, while albumin and globulins were decreased when comparing to normal values. Cows diagnosed with DC had increased concentration of AST, CK, TB, and potassium, while albumin and sodium were decreased compared with normal values. The results of this study may help veterinarians to rapidly and accurately diagnose and treat ill animals, therefore improving disease prognosis.