Why Is My Good Cholesterol So Low? Reading a Low HDL Result
Low HDL can come from inactivity, smoking, high triglycerides, certain medicines or inherited genes, and a doctor reads it with the full panel. This guide, part of Lab Reports Decoded, explains the HDL line on your report, the causes worth checking and what to ask at the next appointment.
Quick facts
- The line: HDL, which the CDC calls “good” cholesterol
- CDC optimal level: at least 40 mg/dL (about 1.0 mmol/L) for men, at least 50 mg/dL (about 1.3 mmol/L) for women
- Main causes: inactivity, smoking, high triglycerides, some medicines, inherited genes
- Fasting: HDL is not affected by fasting; triglycerides rise a little after meals
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Which HDL numbers count as low?
HDL stands for high density lipoprotein. The CDC describes it as “good” cholesterol because high levels can lower the risk of heart disease and stroke. It appears on a lipid profile beside total cholesterol, LDL and triglycerides, and each line answers a different question. A low reading therefore has to be judged against the other lines and against your sex.
The CDC lists the optimal HDL level as at least 40 mg/dL in men and at least 50 mg/dL in women. The table below gives the same levels in mmol/L, in case your report uses that unit, and the mg/dL to mmol/L guide shows the working.
| Sex | CDC optimal (mg/dL) | About mmol/L |
|---|---|---|
| Men | At least 40 | About 1.0 |
| Women | At least 50 | About 1.3 |
A reading of 35 mg/dL, about 0.9 mmol/L, sits under both levels. A reading of 45 mg/dL is above the men’s level but under the women’s, which is exactly why the sex-specific number matters.
A check worth doing on your own report
Find the H or L flag and the range printed beside your HDL line. If that range is one number for everyone, it can mark a reading as normal even when it falls under the optimal level for your sex, so compare your number with the table as well and ask the lab which range it used.
What usually causes a low HDL?
The sources behind this guide point to five areas: how active you are, whether you smoke, your triglyceride level, which medicines you take, and what your genes do. Diet questions, including sugar and chawal, are covered in the high triglycerides diet guide, and the cholesterol food guide covers ghee and fried snacks.
Inactivity and smoking. A 2017 review in Clinical Research in Cardiology lists lifestyle change, including quitting smoking and regular physical exercise, as having a positive effect on HDL, and it recommends that change. Inactivity and smoking are therefore the first habits to look at.
Triglycerides. The CDC notes that high triglycerides together with either low HDL or high LDL can increase the risk of heart attack and stroke. That is why HDL is read alongside the triglyceride line rather than on its own.
Medicines. Beta blockers have been linked with lower HDL in an older review, and the Endotext chapter on monogenic HDL disorders names anabolic steroids among the medications that can lower it. Do not stop or change a prescribed medicine on your own. The prescriber decides what suits you.
Genes. Some low HDL patterns are inherited. The Endotext chapter describes rare single gene disorders, such as familial hypoalphalipoproteinemia, and says variants in many genes, each with a small effect, can add up to a lower HDL. If the number has been low on several tests and a close relative has a similar pattern, ask the doctor whether a family review or genetic testing makes sense.
Is a low HDL dangerous if my LDL is normal?
A low HDL is a reason to read the whole lipid panel, not a diagnosis on its own. A normal LDL does not close the question when triglycerides are also high, because the CDC flags high triglycerides combined with low HDL as a pattern that can raise the risk of heart attack and stroke. A low HDL with normal triglycerides is still worth raising with the doctor, who decides how much it matters by reading the full panel. The lipid profile guide explains each line and the LDL targets.
Does fasting change the HDL result?
No. A 2016 joint consensus statement from the European Atherosclerosis Society and the European Federation of Clinical Chemistry and Laboratory Medicine says HDL is not affected by fasting status, and it recommends routine non-fasting lipid profiles. Triglycerides rise a little after meals, which the statement calls not clinically significant for routine use, but it is still worth asking the lab whether your sample was taken fasting.
When will HDL move after quitting smoking or walking more?
The sources behind this guide give no reliable number of weeks, so treat any fixed timeline you read online as a guess. The 2017 review describes the direction of the change, not its speed. The way to see whether your number has moved is a repeat lipid test, timed by your doctor and taken after a fair run of the new habits.
What to bring to the next appointment
- Note the H or L flag and the range printed beside HDL, then compare your number with the 40 mg/dL level for men or the 50 mg/dL level for women.
- Read triglycerides and LDL alongside HDL, not in isolation, and ask whether your report also prints total cholesterol minus HDL as a separate figure.
- Write down each prescribed medicine with its name and how long you have taken it, and bring the list. Do not stop or change any of them on your own.
- Note how many days a week you do moderate activity and whether you smoke, so the doctor sees what is within your control.
- Ask whether your sample was taken fasting, and whether the repeat test should be taken fasting or not.
- Ask when to repeat the lipid test, and whether a family history of low HDL or early heart disease changes the plan.
Bottom line: a low HDL is a signal to read the whole lipid panel with your doctor, and the sources give no fixed date for the number to move. The usual causes are inactivity, smoking, high triglycerides, certain medicines and inherited genes. One low reading is a reason to read the whole panel, not a verdict on your heart.
You take a heart, blood pressure or anabolic steroid medicine, because some of these can lower HDL. Changing them on your own is unsafe, so raise any worry with the prescriber instead. If you have chest pain, sudden breathlessness or any sudden stroke-like symptom, get urgent medical help rather than waiting for a routine appointment. A family history of early heart disease or very low HDL is also a reason to book a review rather than wait for the next routine test.
Questions people ask about low HDL
What does low HDL cholesterol mean?
Low HDL means the good cholesterol reading is under the CDC optimal level of at least 40 mg/dL for men or at least 50 mg/dL for women. Read it alongside the rest of the lipid profile, because one number is not a diagnosis on its own.
What causes low HDL cholesterol?
The causes covered here are inactivity, smoking, high triglycerides, certain medicines such as beta blockers and anabolic steroids, and inherited gene patterns. Diet questions are answered in the high triglycerides diet guide linked above.
Is low HDL cholesterol caused by genes or lifestyle?
It can be either, and one reading cannot show which. Smoking and inactivity are habits you can change, while a family pattern across several tests is the cue to raise an inherited cause with the doctor.
How does low HDL affect my heart health?
The CDC says high triglycerides combined with low HDL can increase the risk of heart attack and stroke. Your doctor weighs the HDL with the triglyceride and LDL lines, blood pressure and smoking status before deciding what to do next.
Is low HDL dangerous if LDL is normal?
Not automatically. A normal LDL does not close the question when triglycerides are also high, so the doctor reads all the lines together before deciding.
Is an HDL of 35 too low?
Yes, 35 mg/dL, which is about 0.9 mmol/L, sits under the CDC optimal level for both men and women. Ask the doctor what it means alongside your other results.
Can smoking lower HDL?
Yes, in the sense that quitting is listed as a change that raises HDL: a 2017 review lists smoking cessation among lifestyle changes with a positive effect on HDL. The sources behind this guide give no figure for how much smoking lowers it.
Which medicines lower HDL?
Beta blockers and anabolic steroids are two medicines named in the sources behind this guide as able to lower HDL. Never stop or change a prescribed medicine on your own, because the prescriber decides what suits you.
How long does it take to raise HDL after quitting smoking?
No reliable number of weeks appears in the sources behind this guide, so nobody can promise a timeline. A repeat lipid test, timed by your doctor, is the way to see whether the number has moved.
What does low HDL with high triglycerides mean?
It means the doctor reads the two lines together rather than separately, since the CDC flags that combination as one that can increase the risk of heart attack and stroke. Ask what it means for you and when to repeat the test.
Do I need to fast for an HDL test?
No, not for the HDL figure itself. A 2016 joint consensus statement reports that HDL is not affected by fasting and recommends routine non-fasting lipid profiles. Triglycerides rise a little after meals, so ask the lab whether your sample was fasting.
Sources
- Centers for Disease Control and Prevention: About Cholesterol
- Clinical Research in Cardiology: HDL cholesterol: reappraisal of its clinical relevance (2017)
- European Heart Journal: Fasting is not routinely required for determination of a lipid profile (2016)
- Endotext: Monogenic Disorders Altering HDL Levels
- Medical Clinics of North America: Secondary causes of hyperlipidemia (1994)