Coffee and caffeine: what they do to your blood values

Do you drink coffee every morning? For most people, two to four cups fit fine within a healthy pattern, as the Netherlands Nutrition Centre also holds. Still, caffeine can temporarily affect some blood values, and unfiltered coffee is sometimes linked to a slightly higher cholesterol.

My belief after hundreds of blood results: coffee is rarely the culprit, but often a blind spot. People think of fat and sugar, not of the black cup next to it.

This piece is not an argument against coffee. It calmly shows what caffeine and coffee may do to your blood, and what to watch around a test. For the bigger picture, read also our pillar on nutrition and your blood values.

What does caffeine do shortly after drinking it?

Caffeine works fairly fast. Within about 30 to 60 minutes it can raise your heart rate and blood pressure slightly and temporarily. Your alertness goes up too. These effects are usually short-lived and vary a lot per person, depending on tolerance and how much you drink.

An example from practice. You drink two espressos at 8am and have your blood pressure measured at half past eight. That reading can come out a touch higher than your resting value. It says little about your real blood pressure across the day.

People who rarely drink coffee feel the effect more strongly. In daily drinkers, tolerance sets in. That is why caffeine is hard to capture in one number.

Can coffee affect your cholesterol?

Sometimes, and then mainly unfiltered coffee. Unfiltered coffee contains compounds such as cafestol and kahweol, which research links to a slightly higher LDL cholesterol. Think of coffee from a cafetiere, or Turkish and Scandinavian boiled coffee. A paper filter catches most of those compounds.

Filter coffee and coffee from a regular machine contain much less cafestol. Espresso sits in between for filtering. So it is not about coffee itself, but about the preparation.

If you want to know where you stand, LDL cholesterol and total cholesterol are the values that relate. How to read those, you find in our piece on cholesterol and normal values.

Which blood values can coffee or caffeine affect too?

Caffeine and coffee mainly touch a few values, and usually temporarily. It comes down to blood pressure, blood sugar and sometimes cholesterol. The table below sets out, per blood value, what coffee can do and what to watch around your test. See it as an overview, not a diagnosis.

If you want a number of these values measured at once, a basic health checkup fits. Which values make sense for you depends on your situation and your other complaints.

Can you drink coffee before a blood draw?

That depends on the test. For many values, black coffee makes little difference. If you have to draw blood fasting, for example for glucose or cholesterol, it is sensible to drink only water. Coffee with milk or sugar counts as food anyway. If in doubt, ask at the collection point.

Picture an appointment at half past eight for a blood test with fasting values. Best to leave your morning coffee for a moment, or drink it black and mention that. A doctor prefers to look at the pattern than at one coloured measurement.

Caffeine can also touch your night rest if you drink late in the day. Poor sleep can in turn affect your energy and your values. So everything in your lifestyle hangs together.

How much coffee is okay for most people?

For healthy adults, a limit of about 400 milligrams of caffeine per day is often mentioned, roughly four cups of coffee. That is a general guideline, not personal advice. People who are sensitive, sleep poorly or are pregnant often sit lower. Your GP can help decide what fits you.

My view: the panic around coffee is usually overblown. For most people, moderate coffee drinking is fine. The exception is a lot of unfiltered coffee in someone who already has high cholesterol.

If you change your habits, that can show up in your blood over time. As with alcohol, it is about your pattern, not one day. Read about that in what 30 days without alcohol does to your blood values.

Frequently asked questions

Does coffee raise your cholesterol?

Mainly unfiltered coffee can go together with a slightly higher LDL cholesterol, through compounds such as cafestol. Filter coffee has that effect far less. One cup says little; it is about your pattern over a longer time.

Can I drink coffee before a fasting blood test?

For a fasting test, you are better off drinking only water. Coffee with milk or sugar counts as food. Whether black coffee is allowed differs per test, so ask at the collection point or your GP.

Is caffeine bad for your blood pressure?

Caffeine can raise your blood pressure slightly and temporarily shortly after drinking, especially if you are not used to it. In regular drinkers, tolerance sets in. Persistently high blood pressure you discuss with your GP.

What I would suggest

Enjoy your coffee, but stay curious about your preparation and your timing. A lot of unfiltered coffee can nudge your LDL, and caffeine just before a draw can colour your result. If you want to know your values, pick a calm moment and discuss your habits with your doctor. Every blood test result at Vitalcheck includes a professional assessment by a BIG-registered doctor. A blood value is not a diagnosis: always discuss treatment decisions with your GP.

References

• Netherlands Nutrition Centre (Voedingscentrum). Coffee and caffeine. Accessed 2026.
• RIVM. Caffeine and health: figures and context. Accessed 2026.
• Thuisarts.nl. I want to lower my cholesterol. Dutch College of General Practitioners. Accessed 2026.