The RVT Journal: Hyperlipemia
Hyperlipemia (Medical Term)
Meaning: Describes abnormally high levels of fat accumulation in the bloodstream
This can refer to increased Triglycerides (hypertriglyceridemia), increase Cholesterol (Hypercholesterolemia) or both.
One of the 3 macronutrients that supply the body with ENERGY
Fats provide more the DOUBLE the energy / gram compared to proteins and carbohydrates.
Key Function in Diet: Caloric density as well as palatability.
ANATOMY - Function in the body
- Supply essential Fatty Acids which cannot be synthesized by the body in simple terms (types of fats your body needs but cannot make on its own) they must come from the food and are required in the diet.
- Structural components and are required for proper absorption of FAT-SOLUBE VITAMINS (Dissolve in fat and are absorbed along with dietary fats, they can also be stored in the liver and body fat so the body doesn’t need them every day)
FAT-SOLUBLE VITAMINS these include:
- Vitamin A
- Vitamin D
- Vitamin E
- Vitamin K
NORMAL METABOLISM OF LIPIDS:
1st: Requires digestion via both enzymatic and physical components before absorption through a process called: EMULSIFICATION= Bile salts released from the liver form mixed micelles from lipid micelles. Forming a mixed miscelle is necessary (fat on it's own is hydrophobic meaning it's water-fearing it will not mix without being processed). It's mixed micelle form makes it a hydrophilic (water-loving it will mix with or dissolves in water easily) . Mixed micelle carrier allows lipid mixing in the aqueous intestinal environment for absorption.
Translation to simple terms:
Fats can’t be absorbed easily on their own because they don’t mix with water (they’re hydrophobic, or “water-fearing”). But intestines are of a watery environment, so that’s where Emulsification comes in.
- The liver makes bile, which contains bile salts. These act like a detergent (like dish soap breaking up grease).
- Bile salts break big fat droplets into tiny pieces and wrap around them, forming something called a mixed micelle (tiny fat packages).
- These tiny packages now behave in a way that lets them mix with the watery environment (more “water-friendly”).
Because of this, the fats can be carried to the intestinal wall and absorbed into the body.
SUMMERY : Fats don’t mix with water, so bile breaks them into tiny pieces and packages them so they can travel in the watery intestine and be absorbed
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Lipase
Lipase is an important PANCREATIC ENZYME (Digestive enzymes made by the pancreas)
Function: Breakdown fats into fatty acids.
Fatty Acids are then absorbed in the GUT LUMEN ( Term for inside space of the digestive tract) where they are formed into LIPOPROTEINS and enter the bloodstream via the LYMPHATIC SYSTEM.
Translation to simple terms:
Lipase is a digestive enzyme made by the pancreas that breaks fats into smaller pieces called fatty acids.
After fats are broken down:
- The fatty acids are absorbed in the small intestine (gut)
- They are then repackaged into tiny particles called lipoproteins
These particles don’t go straight into the blood. Instead, they:
- First enter the lymphatic system (a transport system in the body)
- Then eventually move into the bloodstream
Summery: Lipase breaks fat into small parts, which are absorbed in the intestine, packaged, and sent into the body through the lymph system before reaching the blood.
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Type of fats are important. Types of fats relevant to HYPERLIPEMIA are TRIGLYCERIDES and CHLOESTEROL.
Triglycerides are the most important form of fat present in food and can be classified in the diet according to types of FATTY ACIDS the triglyceride molecule contains. Classification includes:
- Saturated
- Monounsaturated
- Polyunsaturated
There terminology is based on their molecular structure depending on the number of double bonds on the fatty acid carbon -chains.
Translation to simple terms:
In conditions like hyperlipemia (too much fat in the blood), the main fats we look at are:
- Triglycerides (the main fat from food)
- Cholesterol
Triglycerides are made up of fatty acids, and we group them based on their structure:
- Saturated fats → no double bonds
- Monounsaturated fats → one double bond
- Polyunsaturated fats → many double bonds
Chemistry is confusing no worries! just think of it like this:
- Saturated = fully “packed” (no gaps)
- Monounsaturated = one “bend” in the chain
- Polyunsaturated = multiple “bends”
These “bends” (double bonds) change how the fat behaves in the body.
Summery: Triglycerides are fats made of fatty acids, and they are grouped as saturated, mono-, or polyunsaturated depending on how many bends (double bonds) are in their structure.
Foods that are high in triglycerides (fat) :
- Bacon / fatty meats
- Cheese
- Processed meats (hot dogs, sausage, pepperoni)
- Fried or greasy foods
- Rich, fatty dog treats (bacon & cheese flavored)
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CHOLESTEROL
Often referred to by the lipoprotein it is carried on and the corresponding protein:lipid ratio.
High-Density Lipoprotein (HDL) and Low-Density lipoprotein (LDL) are the most common cholesterol carriers with very low-density lipoprotein (VLOL) and Chylomicrons more commonly being triglyceride carriers.
The majority of the cholesterol in cats and dogs is carried on (HDL) High-density Lipoprtein. These small lipoproteins can transport cholesterol from the Peripheries to the liver for disposal.
(LDL) Low-Density Lipoproteins remain in the peripheries and can accumulate with excess it's possible connection to Cardiovascular disease.
In Veterinary medicine cholesterol and arterial plaque is a less common disorder.
Translation to simple Terms:
Fats and cholesterol travel in the blood using “carrier packages” called lipoproteins.
These carriers are named based on how much protein vs fat they contain (their density).
Main types:
-
HDL (High-Density Lipoprotein)
Think: “good carrier”
Moves cholesterol from the body back to the liver to be removed -
LDL (Low-Density Lipoprotein)
Think: “bad carrier”
Leaves cholesterol in the body tissues, where it can build up if there’s too much -
VLDL & Chylomicrons
Mainly carry triglycerides (fat) instead of cholesterol
In dogs and cats
Most cholesterol is carried by HDL (High-Density Lipoprotein)
This helps move cholesterol away from tissues and back to the liver
Why it matters:
- Too much LDL → cholesterol can build up in the body
- This buildup may be linked to heart and blood vessel problems
Summery: Cholesterol travels in the blood using carriers. HDL carries it to the liver to be removed (good), while LDL can leave it in the body where it may build up (bad).
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Postprandial hyperlipemia is considered normal 6-12 hours after ingesting a meal at triglyceride serum levels under 500-2000mg/dl.
A sample with triglyceride levels greater than 1000mg/dl or greater than 500mg/dl in a patient fasted for more than 12 hours is considered abnormal.
Hyperlipemic serum and plasma can appear milky, white and turbid. Since cholesterol in cats and dogs is carried on HDL lipoproteins, patients with hypercholesterolemia alone will NOT have visible lipemic serum unless also accompanied by HYPERTRIGLYCERIDEMIA why? HDL are the smallest lipoproteins and DO NOT REFRACT LIGHT.
Gross lipemia (medical term for -so much fat in the blood that you can actually see it-) is known to interfere with blood cell counts and biochemical assays. Laboratories will either reject lipemic samples or attempt to improve lipemic samples by using ULTRACENTRIFUGATION ( medical term for process of spinning samples at very high speeds to separate substances based on their density (weight) to clear CHYLOMICRONS).
Lipemia can also lead to hemolysis which may interfere with blood results and this CANNOT be removed. Acknowledgment is warranted of a sample that was cleared prior to interpreting triglycerides concentrations.
Collecting blood when patients (pets) are FASTED can prevent postprandial lipemic samples. If a lipemic sample must be used it best to submit two samples simultaneously. Purpose: One sample can be cleared for regular testing and the other can be reserved and uncleared for TRUEGLYCERIDE ASSESSMENT
Translation to Simple Terms:
After eating (normal vs abnormal)
It’s normal for pets to have more fat in their blood 6–12 hours after eating
But if:
- Fat levels are very high (>1000 mg/dL)
- OR still high after fasting 12+ hours (>500 mg/dL)
That is abnormal (hyperlipemia)
What lipemic blood looks like
Blood can look:
- Milky
- Cloudy
- White
This happens when there are a lot of triglycerides (fat) in the blood.
Why high cholesterol alone doesn’t look milky
- In dogs and cats, cholesterol is mostly carried by HDL (good cholesterol)
- HDL particles are very small, so they don’t scatter light
So:
- High cholesterol alone = clear blood
- High cholesterol + High triglycerides = milky blood
⚠️ Why gross lipemia is a problem
When there’s a lot of fat (gross lipemia):
- It can mess up lab test results
-
Labs may:
- Reject the sample, OR
- Try to fix it using ultracentrifugation (spinning to remove fat particles)
This spinning removes large fat particles like chylomicrons.
❗ Important issue
Lipemia can also cause hemolysis (breaking of red blood cells) this cannot be fixed and may also affect results.
How to prevent problems
Best practice:
- Fast the pet before blood collection (Golden standard)
If the sample is lipemic:
-
Send two samples:
- One cleared (spun) → for regular testing
- One uncleared → for accurate triglyceride measurement
Summery: After eating, some fat in blood is normal. Too much fat makes blood look milky and can mess up test results. Fasting and proper sample handling help get accurate results. You the owner are important and necessary in this step by cooperating and following pre-sample collection instructions.
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Chylomicrons Test
A way to classify hyperlipemia, by distinguishing the TYPE of LIPOPROTEINS present in the sample (very-low density lipoproteins vs. chylomicrons).
Behind the scenes :
- Serum sample is placed upright in the fridge for 6-12 hours. No reagents or equipment is used. Chylomicrons, if present will float to the top and create a cream-like layer on the surface clearing the serum.
Cause: Chylomicrons are he least dense lipoproteins
- If the serum sample remains turbid with no surface layer, it suggests retention of very - low density lipoproteins which is more commonly associated with secondary hyperlipidemia. If both cream layer forms and the sample remains turbid, suggests retention of both lipoproteins which can be seen in poorly regulated CANINE DIABETICS. Disorder of Chylomicron metabolism is the most COMMON form of hyperlipemia in dogs.
Function:
Chylomicrons transport triglycerides from the small intestine through Lacteals (lymphatic vessels in the small intestine). they enter the blood circulation through the thoracic lymph duct, then travel to the capillaries of skeletal muscle and adipose tissue, where lipase hydrolyzes the triglycerides into GLYCEROL and FATTY ACIDS .
This entire process takes 6-12 hours so Chylomicrons still present in a fasted sample greater than 12 hours indicates chylomicrons are NOT adequately cleared from the bloodstream.
Translation in Simple Terms
what type of fat is in the blood can be determined by letting the sample sit in the fridge.
How it works:
- Put the blood (serum) in the fridge for 6–12 hours
- No machines needed
What will happpen:
1. Cream layer on top (like milk cream):
- Means chylomicrons are present
- These are the lightest fat particles, so they float
2. Still cloudy with NO cream layer:
- Means VLDL (very-low-density lipoproteins) are present
- These stay mixed in the blood
3. Cream on top + still cloudy underneath:
- Means both chylomicrons AND VLDL are present
- Often seen in poorly controlled diabetic dogs
Most common in dogs
The most common problem is chylomicron buildup= This means the body is not clearing fat properly after eating
What chylomicrons do
Think of them as fat delivery trucks:
- They carry fat from the intestines
- Travel through the lymph system
- Enter the bloodstream
- Deliver fat to muscle and fat tissue
Then an enzyme (lipase) breaks the fat into:
- Fatty acids
- Glycerol
Why fasting matters
Normally, chylomicrons disappear within 6–12 hours after eating
For accurate results if they are still present after 12+ hours of fasting= The body is not clearing fat properly → abnormal
Summery: Blood sits in the fridge if fat floats to the top, it’s chylomicrons. If it stays cloudy, it’s other fats. If fat is still there after fasting, something is wrong with fat processing.
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Classifying Hyperlipemia
Hyperlipemia is classified as either primary ( FAMILIAL) or as secondary (ACQUIRED).
Primary/Familial hyperlipemia: An inherited disorder of lipoprotein metabolism that is without known underlying cause.
- Rare in cats
- May be more common in dogs. Breed disposition: Miniature Schnauzers
- Life long management is required. With adequate control then prognosis is generally good. Part of it is in your hands watching what you feed your pet once treatment is in place.
Secondary/Acquired: Occurs from an alteration in lipoprotein metabolism secondary to another cause.
- Most common pathological form in veterinary medicine
- Prognosis is significantly dependent on disease management of the underlying cause. Part of it is also in your hands sticking to the requirements of the diagnosed disease/ issue which led to hyperlipemia as a secondary effect.
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Clinical Signs of HYPERLIPEMIA
Vary greatly between the cat and dog, although both species may have no obvious symptoms at all.
In cases of Secondary hyperlipemia, symptoms usually are exhibited from the primary disorder.
Dogs (symptoms are vague and can be similar to pancreatitis or DCM):
- Diarrhea
- Vomiting
- Inappetence
- Abdominal Pain (sensitivity to being picked up from abdomen)
- Lethargy
Cats:
Main symptom: Cutaneous Xanthomas.
Dermatological lesions caused by the accumulation of lipid substances that occur due to affected lipid metabolism. Diagnosed by microscopic evaluation and treatable by managing underlying cause.
- Vary in size and colour from pink to orange
- Isolated lesions or in clusters
- They may appear anywhere on the feline body however most commonly appear : around the eyes, pinnae, abdomen, and paws.
Common disorders with Secondary hyperlipemia:
Endocrine disorder !often the culprit!
- Diabetes Mellitus
- Insulin deficiency impairs the ability to clear chylomicrons from circulation due to insulins role in activating lipoprotein lipase.
- Lack of of lipoproteins will result in triglycerides in chylomicrons accumulating in the bloodstream.
- Hyperlipidemia from diabetes improves/ resolves with GLYCEMIC CONTROL (dietary + medical intervention)
- Hypothyroidism (Cushing's syndrome)
- Hypercholesterolemia has been identified due to cortisol effect of decreasing lipoprotein lipase activity
- Lack of triiodothyronine (T3) hormone leads to increase hepatic cholesterol resulting in decreased lipoprotein lipase activity.
- Correlation between hyperlipidemia and protein losing nephropathy has been detected specifically in patients with PROTEINURIA and decreased PLASMA ALBUMIN.
- Obesity, pancreatitis and cholestatic liver disease may cause secondary hyperlipidemia.
- Hyperadrenocorticism
- Potential : Hepatic and Renal
Diets very high in fat may cause secondary hyperlipidemia
Some prescription drugs can also cause secondary hyperlipidemia
- Progestogens
- Corticosteroids (Prednisone, Prednisolone, dexamethasone)
- Phenobarbital
Avoidance is not the answer- PREVENTION where possible is the GODLEN STANDARD.
Translation in Simple Terms
Many cases of high fat in the blood (hyperlipidemia) are caused by other health problems, especially hormone (endocrine) disorders.
Common causes
Diabetes Mellitus
- Not enough insulin
- Insulin normally helps activate an enzyme (lipoprotein lipase) that clears fat
✅ Good news:
Controlling blood sugar (diet + medication) helps fix the problem
🦋 Hypothyroidism (low thyroid hormone)
- Slows down metabolism
- Causes more cholesterol to be made and less fat breakdown
⚠️ Cushing’s disease (Hyperadrenocorticism)
- Too much cortisol (stress hormone)
- Reduces fat-clearing enzymes
Kidney disease (protein loss)
Losing protein in urine → low blood protein (albumin)
➡️ Body responds by increasing fat levels
Other contributing factors:
- Obesity → more fat in the body
- Pancreatitis → affects fat digestion
- Liver disease → affects fat processing
- High-fat diets → too much fat intake
Certain medications:
Can also increase blood fat levels:
- Steroids (like prednisone)
- Hormones (progestogens)
- Phenobarbital
Avoiding everything isn’t realistic= NO
The goal is prevention and control= GOLDEN STANDARD
✔️ Manage underlying diseases
✔️ Feed appropriate diets
✔️ Monitor pets regularly
Summery: High fat in the blood is often caused by diseases like diabetes or hormone problems. Fixing the underlying issue and managing diet is the best way to prevent it.
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Treatment and Management of Hyperlipidemia
General Goal: Reduce lipid concentrations to within normal range= decreasing the risk of associated health conditions and improving clinical signs.
- Fasted serum triglyceride concentrations should ideally remain less than 5.5mmol/L
- Primary hyperlipidemia is RARE in cats
- Treatment is centered around disease management of the underlying condition.
- Dietary fat restriction - First-line treatment in Dogs
- Specifically hypertriglyceridemia
- Diets should contain less than 12% dry matter (DM) fat or less 4 grams/ 100 kcal metabolizable energy (ME) **This information is on all dog foods on the Guaranteed Analysis
- 2.5grams/100kcal ME can be used with no monitoring for adverse effects required.
- Amount of dietary fat restriction required is relative to the fat content in the current diet, as it is recommended to reduce fat intake by at least 50%
- Fat content from treats should be taken into consideration and should NOT exceed 10% of total daily calories and should have comparable fat content to the diet
- Crude fat percentages on pet food labels
- Are NOT reliable representation of overall dietary fat content
- They only represent minimum values and vary with the amount consumed to meet energy needs
- the importance of grams/kcal ME is more ACCURATE UNIT OF MEASUREMENT
- Supplementation of omega-3 fatty acids + moerdate-fat or low-fat diet can successfully reduced plasma cholesterol and triglyceride levels. Low-fat is more effective.
Translation in Simple Terms:
Main goal
Lower fat levels in the blood to normal
➡️ This helps reduce health risks and improve symptoms
Target level
After fasting, triglycerides should be:
➡️ Below 5.5 mmol/L
General facts
- Primary (genetic) hyperlipidemia is rare in cats
- Most cases are caused by another disease, so: Treat the underlying problem first
Diet = most important treatment (especially in dogs)
First step is feeding less fat
Guidelines:
- Aim for low-fat diets
- Reduce fat intake by at least 50% from current diet
-
Ideal diet:
- <12% fat (dry matter) OR
- <4 g fat per 100 kcal (better measurement)
-
Very safe level:
- ~2.5 g fat / 100 kcal (no close monitoring needed)
⚠️ Treats matter too!
Treats should:
- Be low fat
- Make up less than 10% of daily calories
- Match the diet’s fat level
Label tip (important)
“Crude fat %” on pet food labels:
- Only shows the minimum amount
- Not very accurate
-
grams of fat per 100 kcal (ME)
➡️ This is more precise
Supplements
Omega-3 fatty acids can help:
- Lower triglycerides
- Lower cholesterol
But:
- Low-fat diet works better than moderate-fat diets
When diet isn’t enough
👉 In rare cases:
-
Diet + supplements may not be enough
➡️ Medications may be needed
Summery: The main treatment is feeding a low-fat diet, controlling treats, and fixing any underlying disease. Supplements can help, and medication is only needed in rare cases.
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Pathological Hyperlipemia
Familial or Acquired hyperlipidemia it should be treated as a significant finding that warrants further investigation.
Absence of clinical signs is NOT supportable reason to ignore its significance and therapeutics intervention should be IMPLEMENTED!
Hyperlipidemia has been associated with the development of a variety of secondary health conditions some of which may be LIFE THREATENING:
- Pancreatitis
- Hepatic disease
- Cholelithiasis (gallstones)
- Dermatological disease
- Nervous system disturbances (Seizures and Peripheral Neuropathies)
- Ocular abnormalities which affect vision - Lipid Keratopathy, Lipemic Uveitis, Lipemia Retinalis
Gallstones
Lipid Keratopathy
Lipemic Uveitis
Lipemia Retinalis
Hepatic disease
Nervous system disturbances (Seizures and Peripheral Neuropathies)
These consequences highlight the importance of addressing hyperlipidemia as the significant clinical finding it is !!
While it tends to get brushed off in otherwise "healthy patients" intervening is in their best interest. Hyperlipemia is important and is relevant to the veterinary patient's health status.
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