Two Blood Tests Doctors Should Order – But Don't

Updated July 2026

There are two blood tests that almost everyone should have, yet most people have never heard of, let alone had them done. They are lipoprotein(a) and apolipoprotein B, usually written Lp(a) and ApoB. Each one fills in a gap that a standard cholesterol panel leaves wide open.

What is lipoprotein(a), and why does it matter?

Lp(a) is a genetically determined risk factor for earlier and more aggressive artery disease. Think of it as an extra protein stuck onto your LDL, the bad cholesterol, that makes each particle more dangerous, almost like a heat-seeking missile aimed at your artery walls.

Because it is genetic, there is nothing you can do to change your Lp(a) number. So why check it at all? Because you can get around its effect by lowering your LDL further. Your LDL may be more toxic, but you can make sure there is far less of it around. Medications that lower Lp(a) directly are in development, but it will be a while before they are proven and widely available.

Lp(a) is a once-in-a-lifetime test, since the number does not change. If yours is high, your first-degree relatives, including children, should be screened for it too. But please know that even a very high level is not an emergency. Like every risk factor, it is a signal, not a disease sentence. It simply means we think about your risk a little differently, and lean toward more aggressive cholesterol management and a lower threshold for screening tests like a coronary calcium scan. For the fuller picture on this inherited risk factor, see my deeper dive on lipoprotein(a) and why you should be tested for it.

The good news is that the guidelines finally caught up. As of 2026, the ACC and AHA recommend that every adult have their Lp(a) measured at least once.

What is apolipoprotein B, and what does your LDL number miss?

ApoB tells you something your LDL number cannot, which is how many cholesterol particles you are actually carrying. Unlike Lp(a), ApoB is not locked in by genetics. You can change it.

When your LDL comes back as, say, 130 mg/dL, that is really a measure of weight. Milligrams measure weight, and a deciliter is a measure of volume. So all that 130 truly tells you is that if you scraped the LDL out of a deciliter of your blood and set it on a scale, it would weigh 130 milligrams.

Here is why that matters. LDL is not one type of particle. It is a family of particles, some big, some small, and everything in between. What you do not want is a lot of the small ones. It takes many more small particles to add up to that same 130 milligrams, which means more particles drifting through your bloodstream, more chances for one to bump into an artery wall, and, because they are small, an easier time slipping inside.

Why does ApoB change the conversation?

Because a single ApoB test reveals the particle count that your LDL weight hides. ApoB sits on every LDL particle, exactly one per particle, no matter its size. So comparing your LDL to your ApoB tells the real story. A normal LDL with a high ApoB means you are carrying a lot of small particles.

As a goal, ApoB should sit below 90 mg/dL for most people, and below 70 if you already have heart or vascular disease. Levels under 55 have been linked with actual regression of existing blockages, though reaching that usually takes more than one medication, and your LDL needs to be under 55 as well.

What does this mean for you?

Get both tests at least once, then use what they tell you. Knowing your target ApoB does you no good if the number was never measured in the first place.

Neither test is urgent, but each adds real nuance to your risk. Lp(a) does not change, so once is enough. ApoB does change, including in response to how you eat, so it is worth rechecking over time and treating as part of your prevention checklist. The point is not to make your LDL number look pretty. The point is to reduce your risk. All of it.

Whatever your Lp(a) or ApoB turns out to be, your first and best move is the same. Eat in a way that lowers LDL. That means plenty of whole food fiber, the right healthy fats, and plant sterols from your food. Getting the right amounts of all three is not easy, which is exactly why we built Step One Foods to do it for you.

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