Preventive Screening Tests by Age: What Should You Ask Your Primary Care Doctor?

Medicine is 90% prevention and 10% treatment, so let us take on the age-old question: which screening tests are recommended based on age?

There are many labs that charge patients exorbitant amounts of money for tests that are futile. Avoid those cash-pay 300-panel lab tests. They are of no consequence and mostly have little scientific evidence behind them for making any meaningful change in your lifestyle or habits.

The goal is not to order every test available. The goal is to order the right test, at the right age, based on your risk factors, family history, symptoms, and long-term health. That conversation is what a good annual physical is for.

Fasting Before Labs

Many patients ask what to eat, whether to fast the day before, and what to do on the day of labs. This is an age-old contentious issue for patients and doctors alike.

A smart approach is to get your labs done early in the morning so you can eat breakfast right after the blood draw. Later in the day is fine too, as long as your doctor has your medical history and you do not have hypertriglyceridemia, which we discuss in detail below.

The labs that get affected by food are your lipids and your sugar levels. Not A1c. A1c is an average of roughly three months of your sugars and is therefore not affected by the sugar level on the day of the blood draw.

Again, the main lab that gets affected is your triglycerides. If you suffer from hypertriglyceridemia, then fasting without any food for 8 to 12 hours is recommended. If you do not, then it is not really necessary. If you have very high triglycerides, it can actually influence your LDL as well.

Some patients do not drink enough water because they think fasting means avoiding both liquids and solids. That is not what we recommend.

Have water before labs unless your doctor has specifically told you not to.

A small piece of toast with black coffee is likely another safe choice if you have diabetes or sugar-related problems and are taking medications that can make your sugars go dangerously low, in case the wait at the lab turns out to be long.

If you fast more than 24 to 48 hours, your cholesterol panel may actually come back worse.

When Fasting Actually Matters

Fasting is specifically recommended when we are diagnosing or following a triglyceride disorder. Triglycerides are a subtype of cholesterol affected by the sugar content in your blood, and they vary after meals. That variation can make calculated LDL-C falsely low, in other words giving you false reassurance that your bad LDL is fine when it is not, especially after a very fatty meal.

If a non-fasting triglyceride result comes back above 400 mg/dL, a fasting lipid profile is strongly recommended. That is obtained in this specific subset of patients, not in everyone.

Total cholesterol and HDL-C are minimally affected by fasting. Apolipoprotein B and Lp(a) are unchanged after meals as well. So fasting applies to a very narrow set of patients and is not universally required, despite being an age-old recommendation that most people follow without understanding the rationale.

One exception. If this is your very first lab test ever, yes, that one needs to be fasting, so your triglycerides are documented correctly. If they come back normal, then every year after that, fasting is not required.

Age 18 to 44

Anyone 18 to 44 years of age is in the carefree stretch where everything still works smoothly, before the downward slope of wear and tear on body parts.

Staying healthy by exercising three to four times a week, avoiding smoking and excess alcohol, and staying hydrated will prevent the most common diseases in the long term.

Diabetes Screening

Diabetes is assessed with a lab called A1c, and it is one of the most important labs for determining your future chances of developing the disease.

The encouraging part is that if you keep your A1c below 5.7, you can stay away from diabetes even if you are genetically predisposed through family history.

Patients with a family history of diabetes, central obesity, weight gain, high blood pressure, high cholesterol, or symptoms of high sugar should discuss diabetes screening with their primary care physician.

As a rough check, though not a very accurate one, when your morning blood sugars run between 100 and 125 you are usually in the prediabetic range, and once they start running above 126 there is a good chance you will be diagnosed with diabetes. Blood sugar measurement alone gives only a rough estimate, not a conclusive diagnosis. A1c is the standard we follow for diagnostic purposes.

High Blood Pressure

Hypertension, also called high blood pressure, is measured with a machine. Do not measure it when you are anxious, running around, stressed, drinking coffee, or right after exercise.

The proper way is to sit quietly for five minutes, then measure your blood pressure two to three times, and take the average.

If your systolic blood pressure, the top number, is more than 130, you may have stage 1 hypertension and may need medication if it persists despite diet, exercise, weight loss, and salt reduction.

If your systolic is more than 140, you may have hypertension, provided that is recorded on two separate days.

Cholesterol and LDL

Cholesterol is measured with a blood sample.

We check LDL levels because LDL is the important factor that determines your long-term risk for heart attack, stroke, and other diseases that happen due to clogging of the arteries. This is usually what doctors look at most closely when evaluating your future risk. If your numbers are running high, that is worth a dedicated cholesterol visit.

Lipoprotein(a)

Per the 2026 ACC/AHA Guideline on the Management of Dyslipidemia, Lipoprotein(a), also called Lp(a), should be checked at least once in adulthood.

This is not a regular cholesterol number. It behaves more like a genetic test. It usually does not change much with diet, exercise, or ordinary lifestyle changes, which is why we do not have to keep repeating it every year.

The reason we check it is that when Lp(a) is high, your risk of heart attack, stroke, and gunk building up in your arteries goes up significantly.

It raises that risk in three ways.

It speeds up the buildup of gunk in the artery walls.

It causes inflammation in those walls, and inflamed walls attract even more gunk to stick to them.

It makes your blood more likely to form clots, and those clots add to the buildup inside the vessel.

If your Lp(a) is elevated, we push your LDL, the bad cholesterol, lower and harder than we would for someone whose Lp(a) is normal.

We do not chase the Lp(a) number itself. That number is set by your genes and does not move with medication. What we chase is the risk behind it, so we lower everything we can control to protect your heart and your brain.

An Lp(a) of 50 mg/dL or higher counts as a risk-enhancing factor for ASCVD, which is the medical term for gunk building up in the arteries.

Above 180 mg/dL puts you in the highest risk group. At that level we get very aggressive with both lifestyle changes and medication.

Who Should Be Tested Early

Testing is also reasonable in individuals with premature ASCVD, meaning a personal or family history of early heart disease or stroke, severe hypercholesterolemia with LDL above 190, or suspected familial hypercholesterolemia.

Familial hypercholesterolemia means cholesterol runs strongly in the family. Many family members may carry a diagnosis of high cholesterol, and these individuals may be thin or of normal body weight and still have very high LDL, usually in excess of 190.

Some parents ask me whether it is worth checking Lipoprotein(a) in children.

My answer is that it depends.

If the parents have familial hypercholesterolemia, or even suspected familial hypercholesterolemia with LDL above 190, or there is a strong family history of early heart disease or stroke, then yes, we may check early and even treat early.

ApoB

ApoB is another test. It is usually checked to help guide lipid-lowering therapy in individuals with known atherosclerotic disease, in other words gunk in the arteries made of yellow cholesterol mixed with other components like platelets and fibrin, which can form clots and reduce blood flow to tissues.

When blood flow goes down, oxygen supply goes down. That is how patients end up with heart attack, stroke, kidney disease, and circulation problems.

ApoB also has utility in patients with type 2 diabetes, cardiovascular-kidney-metabolic syndrome, high triglycerides, metabolic risk, or known artery disease.

A persistently elevated ApoB of 130 mg/dL or higher is considered an ASCVD risk-enhancing factor.

We may measure ApoB more than once in selected patients to assess how well cholesterol-reducing medications are working.

So if ApoB is still high despite a normal LDL, we manage more aggressively rather than stopping at LDL alone.

CBC

CBC, short for complete blood count, is most useful for reproductive-age women, but both men and women can have conditions that affect your soldier cells, the white blood cells.

This test helps us identify anemia, infection, inflammation, low platelets, and sometimes bone marrow dysfunction.

Your white and red blood cells are produced in your long bones, and bone marrow can get mad and start producing abnormal cells.

Early testing is key, because we have medications that can slow the progression of many blood cancers.

Red blood cells are the main carriers of oxygen from your lungs to the rest of your body, which is made possible by the hemoglobin inside them.

We measure subtypes of cells like monocytes, eosinophils, and basophils, and we look for broken cells or abnormal shape and size, which can point to early bone marrow problems such as leukemia.

Kidney Function Test

The kidney function test includes a blood test called a BMP, or basic metabolic panel.

The important value is blood creatinine. This is not the same as the sound-alike creatine used in gyms, and there is no relationship between the two.

We also like to check the urine for protein, which can alert us to early kidney damage.

There is a specific urine test we run yearly on diabetic patients called urine microalbumin. It looks for the smallest protein particle slipping through the mesh of the kidney’s filtering cells, which tells us to look deeper into kidney function and order further tests to rule out different kinds of kidney disease.

Kidney specialists identify five stages of kidney disease. Catching it in stages 1 and 2 can sometimes prevent worsening, but once you reach stage 3 chronic kidney disease, the chances of progression are higher if risk factors are not controlled.

Thyroid Function Test

We check thyroid function with a blood test as well.

Thyroid problems can cause fatigue, weight changes, constipation, diarrhea, palpitations, anxiety, hair changes, mood changes, and temperature sensitivity, as if you always feel cold or warm. Feeling cold can also have other causes, such as iron deficiency with or without anemia, which is common in reproductive-age women.

Vitamin B12

B12 is important for the maturation of your red blood cells, which is why deficiency shows up as chronic fatigue. It also builds the important sheath around your nerve cells.

The analogy is a plastic cover around a copper wire. B12 makes the myelin sheath around nerve cells, so a deficiency affects memory and sensation, especially if you are feeling numbness, tingling, burning, or weakness. Watch for more on B12 in an upcoming post.

Vitamin D

Vitamin D has many important functions, mainly keeping your bones healthy and helping if you have bone pain, constipation, and fatigue.

It can be an expensive test, so make sure your primary care doctor uses the diagnosis codes the insurance company requires. Otherwise you may end up paying for the test yourself.

Screenings for Women

Every three years after age 21, get a Pap smear done, either by your primary care doctor or your gynecologist.

It is a very simple procedure where your doctor uses a special brush to collect a sample of cells, which are then examined for cancerous changes.

After age 40, get a mammogram to screen for breast cancer. It is done at a radiology office, where the breast is imaged for calcifications or other findings that point toward breast cancer. It is a very important test, because early detection saves lives.

We may check testosterone in women who have specific symptoms such as low libido, particularly around menopause, and may offer treatment if appropriate after discussing the risks and benefits.

Screenings for Men

PSA testing is a decision we discuss and order based on the patient’s underlying risk.

The reason is that these tests, when abnormal, can sometimes create unnecessary anxiety and lead to more testing, biopsies, and procedures that may or may not be needed.

That is why we target PSA testing by risk, such as men with African ancestry, a strong family history of early prostate cancer, or concerning urinary or prostate symptoms.

Testosterone helps us identify issues with libido, fatigue, mental fogginess, low energy, and sometimes erection problems.

Low testosterone is always confirmed with repeat morning lab tests, ideally between 8 and 9 a.m., because that is when your testosterone level is highest.

Testosterone supplements usually do not fix erection problems on their own, but supplementation may help selected patients with low libido, fatigue, mental fogginess, and a confirmed low testosterone level.

Age 45 to 65

Everything above still applies, with more focus on hormone changes, heart risk, cancer screening, bone health, and chronic disease prevention.

Colon Cancer Screening

Everyone is recommended to begin colon cancer screening at age 45, because the chances of colon cancer start to rise at this age.

This can be done with a colonoscopy every 10 years, or stool testing for cancer DNA every three years, depending on your risk.

Discuss the right choice with your primary care doctor. If you have a history of polyps or a family history of colon cancer, you should not be relying on stool testing alone. In many of those cases, colonoscopy is the better option.

Hormone Changes

This is the age when hormones, especially estrogen, start getting whacky, and generally start dropping.

It is especially troublesome for women around menopause, who get sleepless nights, anxiety, anger, mood changes, and night sweats.

Your primary care doctor can prescribe HRT, hormone replacement therapy, after evaluating safety guidelines, your personal risk, your family history, and your symptoms.

Bone Density or DEXA Scan

Another test, especially for menopausal women and men with low testosterone, is a bone density scan, also called a DEXA scan. It is a special scan that checks how dense your bones are.

If it comes back low, your doctor can prescribe medications that improve bone density and reduce your risk of fractures.

Age 65 and Older

You are most likely getting retired here and planning to spend the golden years in peace.

Without proper health checks, sudden complications can arise that are costly not just financially but in quality of life.

All the labs and tests mentioned above for ages 18 to 65 still apply, depending on your medical history.

On top of that, we recommend a yearly eye exam to check for cataracts, and a whisper test or tuning fork test in the office to check your hearing.

This matters because you start to lose brain cells more rapidly when you have a sensory deficit from poor eyesight or reduced hearing, which can accelerate memory loss.

We also check for any cognitive decline and discuss advance care directives when relevant.

Your doctor may see you more often if you have a major chronic disease such as diabetes, hypertension, or high cholesterol, or a history of stroke or heart attack. Otherwise, checkups twice a year are usually sufficient.

Talk to Your Doctor About What You Actually Need

If you are due for your annual physical, preventive screening tests, or routine lab work, you can schedule an appointment with Quality Primary Care Associates to discuss which tests are appropriate for your age, symptoms, family history, and medical risk factors.