What it measures.
HDL particles are involved in reverse cholesterol transport—moving cholesterol from tissues back to the liver for excretion. While higher HDL has traditionally been considered protective, recent research shows that HDL function and particle count may matter more than cholesterol content.
HDL-C measures the amount of cholesterol carried by high-density lipoprotein particles. HDL particles are smaller and denser than LDL, containing more protein relative to fat. They perform multiple functions including cholesterol efflux, anti-inflammatory activity, and antioxidant protection.
Why it matters.
Low HDL is consistently associated with increased cardiovascular risk, particularly in the context of metabolic syndrome. However, drugs that artificially raise HDL haven't reduced heart disease, suggesting HDL is a marker of metabolic health rather than a direct therapeutic target.
Physiology.
HDL particles are synthesized in the liver and intestines. They collect excess cholesterol from peripheral tissues, including artery walls, and transport it back to the liver (reverse cholesterol transport). HDL also has anti-inflammatory, antioxidant, and anti-thrombotic properties. Its function depends on the quality and composition of particles, not just cholesterol content.
Testing & preparation.
How to prepare
- Fasting traditionally recommended but not strictly required for HDL
- Avoid alcohol for 24 hours (can acutely raise HDL)
- No intense exercise day of testing
When to test
Part of standard lipid panel. Should be assessed with triglycerides to calculate TG/HDL ratio.
How often
Every 1-2 years as part of routine lipid screening; more frequently if addressing metabolic syndrome.
Interpretation.
High hdl cholesterol
Common causes:
- Regular aerobic exercise
- Moderate alcohol consumption
- Genetic variants (CETP deficiency)
- Some medications (niacin, fibrates)
- Healthy lifestyle overall
Implications:
- Generally indicates good metabolic health when from lifestyle
- Very high levels (>100 mg/dL) may not add protection
- Genetically elevated HDL may have paradoxically higher risk in some cases
- Must interpret in context with other metabolic markers
Low hdl cholesterol
Common causes:
- Sedentary lifestyle
- Smoking
- Obesity, especially visceral fat
- Type 2 diabetes and insulin resistance
- High triglycerides (inverse relationship)
- Certain medications (beta-blockers, anabolic steroids)
- Genetic factors
Implications:
- Marker of metabolic dysfunction
- Associated with insulin resistance
- Increased cardiovascular risk when combined with high triglycerides
- Often accompanies the 'atherogenic dyslipidemia' triad
Optimization.
Diet
- Olive oil and other monounsaturated fats may modestly raise HDL
- Moderate alcohol (1 drink/day) raises HDL but risks may outweigh benefits
- Reduce refined carbohydrates and sugar (improves TG/HDL ratio)
- Include fatty fish regularly
- Mediterranean dietary pattern associated with better HDL function
Lifestyle
- Aerobic exercise is the most effective HDL raiser (10-15% increase)
- Quit smoking (can raise HDL 5-10%)
- Weight loss, especially visceral fat reduction
- Adequate sleep (poor sleep lowers HDL)
- High-intensity interval training may be particularly effective
Supplements
- Niacin: effective but side effects and lack of outcomes benefit limit use
- Omega-3s: modest effect on HDL function if not quantity
FAQs.
Is higher HDL always better?
Not necessarily. While low HDL is clearly associated with higher risk, very high HDL (>100 mg/dL) may not provide additional protection and in some genetic variants may even be associated with increased risk. Quality and function of HDL particles matter more than raw cholesterol content.
Why didn't HDL-raising drugs work?
Drugs that artificially raised HDL cholesterol (like CETP inhibitors) failed to reduce cardiovascular events. This suggests HDL is a marker of metabolic health rather than a direct driver of protection. You can't 'drug' your way to good HDL—it must reflect genuine metabolic fitness.
What's the best way to raise HDL?
Regular aerobic exercise is the most effective intervention, potentially raising HDL 10-15%. Quitting smoking, losing weight (especially visceral fat), and reducing triglycerides through carbohydrate restriction also help. Focus on overall metabolic health rather than HDL alone.
Why is my HDL low despite exercise?
Low HDL can persist despite exercise if insulin resistance or metabolic syndrome is present. Check triglycerides, fasting insulin, and waist circumference. Addressing the underlying metabolic dysfunction will help. Some people also have genetic variants that keep HDL lower.
Does the TG/HDL ratio really predict insulin resistance?
Yes, the TG/HDL ratio is an excellent surrogate marker for insulin resistance, validated in multiple studies. A ratio <2.0 suggests good insulin sensitivity; >3.0 strongly suggests insulin resistance. It's most useful in non-Hispanic white and Mexican American populations.