Rectal temperature   100-103 F (37.8 - 39.4 C), 101.9 average
Heart rate           216-250/min (225 average)
Respiration          33-36/min
Urine pH             6.5-7.5; mild to moderate proteinura is common and normal
Blood volume         60-80 ml/kg

The following information comes from "Normal Parameters and Laboratory
Interpretation of Disease States in the Domestic Ferret," an article
written by Dr. Tom Kawasaki around 1994.  Your veterinarian might find
this information helpful.

                            mean    acceptable range
sodium (mmol/L)             153     143-163
potassium (mmol/L)          4.47    3.2-5.77
chloride (mmol/L)           116     105-127
calcium (mg/dl)             8.8     7.5-10.1
inorganic phosphorus (mg/dl) 5.5     3.7-7.4
glucose (fasted) (mg/dl)    110     65-164
BUN (mg/dl)                 21      8-37
creatinine (mg/dl)          0.5     0.16-0.84
BUN/creatinine              42
total protein (g/dl)        5.8     4.4-7.3
albumin (g/dl)              3.3     2.5-4.1
globulin (g/dl)             2.2     1.8-2.9
total bilirubin (mg/dl)     0.2     0.1-0.5
cholesterol (mg/dl)         174     76-272
alkaline phosphatase (IU/L) 37      15-75
ALT (IU/L)                  95      13-176
AST (IU/L)                  61      23-99
CO2                         22      14-30
A/G (g/dl)                  1.3     1.0-2.3
LDH                         274     101-498
triglycerides               98      31-101
GGT                         4.8     1-13
uric acid                   2.2     1.4-3.3
PCV (%)                     45.4    38-54
hemoglobin (g/dl)                   13-18
RBC (X10^6/mm3)             9.0     7.0-11.0
platelets (X10^3)           400     350-600
reticulocytes (%)           N/A
WBC (x10^3/mm3)             5.22    2.8-8.0
neutrophils                 3017    2329-5700
                            (59%)   (39-85%)
lymphocytes                 1157    525-3500
                            (35%)   (11-55%)
monocytes                   119     52-177
                            (2.6%)  (0.76-4.4%)
eosinophils                 133     29-432
                            (2.8%)  (1-8%)
basophils                   0       0
MCV (um3)                   51      46-65
MCH (pg)                    17.7    15.5-19.0
MCHC                        33      29-36 *

Dr. Susan Brown also notes that the normal insulin level is 0-20, but
that insulin may appear normal even in animals with insulinoma [1.1].

There are, of course, dozens of components in your ferret's blood
which can help your vet determine what's wrong.  Here are some of the
ones people ask about most often, and normal ranges.  If you want to
know more about what your ferret's tests mean, don't hesitate to ask
your vet.

The following information is extracted from an article in
The FAIR [Ferret Adoption, Information & Rescue Society] Report,
Vol. II, No. 2, by Mary Van Dahm, with a few additions.

Blood glucose
  Glucose is a sugar, the main energy source for the body.  Its level 
  varies through the day, higher just after a meal, lower when the
  ferret is hungry, but the body keeps it fairly constant mainly by
  controlling the amount of insulin in the blood.  A non-fasted blood
  glucose test might give values up to 207 mg/dl, depending on when
  the ferret last ate.  Testing the blood glucose after withholding
  food from the ferret for 6 hours (fasting blood glucose) eliminates
  the variation and gives you a more definite number to judge it by.
  A low reading (hypoglycemia) may be a sign of insulinoma (see the 
  Ferret Insulinoma FAQ [1.1]).  A high reading (hyperglycemia) is
  rare, but might be a sign of diabetes.  However, insulinoma can
  also cause a high glucose reading, and since diabetes is extremely
  rare in ferrets, you should double-check any diabetes diagnosis by
  looking for sugar in the urine as well.

Pack cell volume/hematocrit (PCV/HCT)
  This is the percentage of red blood cells in the blood.  Low
  readings indicate anemia; high readings are usually a sign of
  dehydration. 

Red blood cells (RBC)
  Red blood cells carry oxygen to the body's tissues and carbon
  dioxide back to the lungs.  Low readings show anemia. 

White blood cells (WBC)
  Part of the immune system.  Readings over about 7000 may mean
  the ferret is fighting off an infection, cold or flu.  Readings over 
  10,000 may be early signs of lymphoma (see the Ferret Lymphosarcoma
  FAQ [1.1]) or another cancer.  Unusually low readings indicate anemia 
  and a bone marrow problem. 

Lymphocytes
  Another type of white blood cell.  High readings can indicate a 
  "smoldering" infection, possibly Helicobacter mustelae (see the
  Ferret Gastric Ulcer/ H. mustelae FAQ [1.1]).  Many, but not all, 
  cases of lymphosarcoma also show elevated lymphocyte levels (see the
  Ferret Lymphosarcoma FAQ [1.1]).

Eosinophils
  Another type of white blood cell.  Often an indicator of intestinal 
  disorders, infection, or cancer.  Other parts of the blood profile 
  must also be considered for a diagnosis.

Protein, Albumin and Globulin
  Albumin is a kind of protein, and globulin is a general term for all 
  proteins that aren't albumin, so protein - albumin = globulin.  The 
  numbers indicate the ferret's general health and nutrition, and 
  albumin also helps show how well the liver and kidneys are working.

BUN and Creatinine
  The job of the kidneys is to filter out impurities, so if they
  aren't working well, these levels will be high. 

Alkaline phosphatese
  This is an enzyme found in the liver and bone.  When bones are
  growing or the liver is damaged, lots of this is released into the
  blood. 

Total bilirubin
  A by-product of the normal breakdown of hemoglobin in red blood
  cells.  Helps diagnose liver disease and bile duct obstruction. 

Sodium, Potassium and Chloride
  Controlled by the kidneys, these are commonly called blood
  electrolytes.  They are involved in water balance, acid/base balance,
  and the transmission of nerve impulses, especially to the heart. 

Calcium and Phosphorus
  These minerals are controlled by the parathyroid glands and the
  kidneys.  The levels show possible problems with bones, blood
  clotting, and nerve, muscle, and cell activity.

References:
  1. Wellness, Inc. How to Read Your Report,  1993 
  2. Finkler, M. Practical Ferret Medicine and Surgery for the Private
          Practitioner, 1993
  3. Brown, S.  Ferret Medicine and Surgery, 1992
  4. Fox, JG.  Biology and Diseases of the Ferret, 1988 *