Yes, you need to fast. We ask for 10 to 12 hours without food before your Cardio Res-Q blood draw, so that the lipid and insulin results are accurate. For most people the simplest way is to stop eating after dinner and have blood drawn the next morning.
The same fast applies to both assessments, the Comprehensive ($775) and the Enhanced ($999), because both include the same lab panel. Below is why the fast matters, which results it affects, and what to check with our team about water, coffee and medications.
Key takeaways
- Plan a 10 to 12 hour fast, most easily overnight, before your Cardio Res-Q labs.
- Food changes triglycerides, glucose and insulin the most, and barely touches ApoB or Lp(a).
- Plain water is generally fine during a lab fast, but confirm drinks and medications with our team.
- If you take insulin or other diabetes medication, get instructions from your prescriber before you fast.
- If you ate by mistake, say so before the draw.
Which results a meal can change
Not every test on the panel reacts to food. The ones that do are the reason for the fast.
| Test | Changed by a recent meal? | Why it matters |
|---|---|---|
| Triglycerides | Yes, they rise | Fat from the meal is still circulating |
| Insulin and glucose | Yes, strongly | Both rise after eating, so only a fasting value shows your baseline |
| LDL cholesterol | Slightly | The reported value can dip a little after eating |
| ApoB and Lp(a) | No | Particle counts are stable across the day |
| A1c | No | It reflects average blood sugar over months |
The size of the lipid effect has been measured. In a European consensus review of fasting and non-fasting lipid tests, triglycerides averaged about 26 mg/dL higher in the hours after ordinary meals, and LDL cholesterol about 8 mg/dL lower.1 The same review found that ApoB and Lp(a) were not affected by whether people had fasted.1
That last point is worth a moment. ApoB reflects the total number of cholesterol-carrying particles that can drive plaque, which is one reason it is a steadier measure than a calculated cholesterol value.2
Why insulin is the main reason to fast
The Cardio Res-Q panel measures insulin and glucose together to look for early insulin resistance. Both respond directly to food. After a meal your blood sugar rises and your pancreas releases insulin to bring it down, so a reading taken then mostly reflects what you ate.
A fasting value is different. It shows how much insulin your body needs just to hold blood sugar steady at rest. That is the number your provider is looking for. Our page on insulin resistance explains what the result means.
If your own doctor says fasting is optional
You may have been told that cholesterol tests no longer need a fast. For a routine lipid panel, that is a fair summary: the European consensus statement cited above recommends non-fasting samples for routine lipid profiles, because the differences are small.
The advice does not transfer to this panel. A Cardio Res-Q draw includes insulin and glucose, and it is meant to be a baseline you can compare against later. Fasting the same way each time keeps those comparisons clean. So for this visit, fast.
How to fast: the practical part
- Count back from your appointment. For a morning draw, finish dinner 10 to 12 hours earlier and eat nothing after that. Schedule the draw at least a week before your consult, so Dr. Varano has the results to review with you.
- Do not stretch it. We ask for 10 to 12 hours, not longer. A much longer fast is not what the test calls for and makes you more likely to feel unwell.
- Water. As a general rule, plain water is allowed during a lab fast, and being well hydrated makes the blood draw easier. Confirm with our team.
- Coffee, tea and everything else. The program page does not say what you may drink. Until our team tells you otherwise, assume water only. That means no cream, sugar, juice, or other drinks with calories.
- Alcohol. Alcohol can raise triglycerides, so skipping it the evening before is sensible. Ask our team if they have a specific rule.
- Bring a snack to eat as soon as the draw is done.
Medications and diabetes: ask before you fast
Do not skip or stop a prescribed medication on your own. Ask our team whether to take your usual morning doses before the draw or bring them with you to take afterward.
This matters most if you take insulin or other medication that lowers blood sugar. Fasting while on these can cause low blood sugar. Get specific instructions from your prescriber before you fast, and tell our team when you book so the draw can be planned safely.
If you eat by mistake
Tell the staff before the draw. A handful of nuts at midnight or milk in your coffee is not a disaster, but your provider needs to know in order to read the results correctly. Whether the draw goes ahead or is rescheduled is the team's call, and the program page does not describe a policy, so ask.
What you should not do is stay quiet. An unreported meal can make triglycerides and insulin look worse than they are, and your plan is built from those numbers.
Does the imaging need a fast?
The 10 to 12 hour instruction is for the labs. If you chose the Enhanced Assessment, the CIMT ultrasound and calcium scan are separate. The calcium scan is done at an outside imaging center with no contrast dye, and that center gives its own instructions. If your provider adds an EndoPAT test, which is done in our office, arrive fully fasted and with no caffeine. See how to prepare for a calcium scan.
How to book your assessment
Go to the Cardio Res-Q program page, select the Comprehensive ($775) or Enhanced ($999) assessment, and pay online. Both are direct-pay and are not billed to insurance. You are welcome to try an HSA or FSA card, but the clinic cannot confirm it will be accepted. If you have questions about fasting with a health condition, contact our team before you book.
This assessment is for people without symptoms. If you have chest pain, pressure, shortness of breath or fainting, call 911 or see a doctor now.
Are You a Candidate for Cardio Res-Q?
Three quick questions about the risk factors we screen for. Your answers stay between you and the clinic.
Frequently asked questions
Can I drink water while fasting?
Plain water is generally allowed during a lab fast and helps with the blood draw. Our program page does not spell out drink rules, so confirm with our team when you book.
Can I have black coffee?
Ask our team. Policies on black coffee differ between clinics and labs, and ours is not published. If you cannot get an answer in time, the safe choice is water only.
Should I take my morning pills?
Do not stop any prescribed medication on your own. Ask our team whether to take your usual doses before the draw. If you take insulin or other diabetes medication, ask your prescriber how to fast safely.
Is a 14 or 16 hour fast better?
No. We ask for 10 to 12 hours. Going much longer is not needed and can leave you lightheaded.
Do I need to fast for Lp(a) or ApoB alone?
Research shows these two are not affected by a recent meal. They are drawn together with insulin, glucose and triglycerides in the Cardio Res-Q panel, though, so the fast still applies to your visit.
Related reading
This article is for general education and is not medical advice. Decisions about testing and medication should be made with your clinician. If you have chest pain or other symptoms of a heart attack, call 911.
