Choosing a test

Anyone can buy a blood test. You do not need a referral or a specific reason.

But before you do, you need to know how to tell a good test from a bad one, because from the outside they look the same. This advice applies anywhere you buy blood tests, not just here.

We cannot tell you which test is right for your health. That needs a clinician who knows your history, and we are not that. What we can do is show you how a well-built test differs from a badly built one, so you can judge for yourself.

1. The price you see is not the price you pay

Almost every seller quotes the test price and adds the blood draw afterwards. That is not dishonest, but it means the number on the product page is rarely the number that leaves your account.

Our thyroid profile is £45. Here is what it actually costs, depending on how you have your blood taken:

So a £45 test can cost £110. That is not a trick. It is what a trained professional taking your blood actually costs.

This is the reality of testing privately: you pay for every step. The kit, the draw, the laboratory, the postage. Those costs exist in the NHS too, they are simply never itemised for you. Every private seller has the same stack. The only real question is whether they show it to you before you reach the basket or after.

What to do: add the draw fee to the headline price before you compare anything with anything. Do it on our site too.

2. A marker count is not a marker list

“Over 50 biomarkers” tells you nothing on its own. Fifty markers of what? A test can reach a high count by including twenty parameters from a single blood count, or by adding cheap markers that duplicate each other.

The count is a headline. The list is the product.

Watch the upgrades especially. It is common to find that the dearer version of a test has a higher marker count but has quietly dropped one of the genuinely useful markers from the cheaper one, replacing it with several cheap ones that push the total up. The number goes up. What you learn goes down.

What to do: find the full marker list before you buy. If it is not published, that is your answer. And if you are comparing two tiers from the same seller, check that everything in the cheaper one is still in the dearer one. We publish the exact list on every product page, including which markers are venous-only and which tests report one fewer marker on a finger-prick sample.

3. Some markers only work if the sample is taken at the right time

A few markers give you a meaningless number unless the sample is collected under specific conditions. Almost nobody tells you this before you buy, and a marker sold without that warning is worth very little.

Cortisol is the clearest example. Cortisol peaks shortly after you wake, roughly one to three hours in, then falls steadily through the rest of the day. Take the sample outside that window and the result is inaccurate and, frankly, useless — because the reference range it gets measured against assumes a morning collection.

That does not make cortisol a bad test. It is a very useful marker, and the timing is the entire point of it. It makes cortisol a bad thing to bury inside a test someone might collect at four in the afternoon.

That is exactly why we sell cortisol as an add-on rather than including it in a panel. If you want it, buy it deliberately and book a morning appointment one to three hours after you wake. Then you get something useful out of it.

What to do: for anything you are considering, check whether it contains a marker that needs specific timing, and whether you can actually meet it.

4. What to sort out before the day of your test

• Glucose needs a 10 to 12 hour fast, water only. In practice that means overnight: eat your evening meal, sleep, test in the morning. It is the only marker on our menu that requires it.
• Cortisol must be collected one to three hours after you wake, timed against your waking hour rather than the clock.
• Testosterone and prolactin read most reliably between 7am and 10am.
• Female hormones depend on cycle day: usually days 2 to 5 for FSH, LH and oestradiol, and day 21 of a 28-day cycle for progesterone.

Fasting helps more than just glucose. Triglycerides rise after a meal, which drags calculated LDL with them. Liver enzymes and iron both move with food. None of those become invalid if you have eaten, but they do move.

And this is the part most people miss. If you test the same markers again in six months, the single biggest thing you control is whether both samples were taken under the same conditions. Fasted, early morning, every time. Do that and the second number is genuinely comparable with the first. Change the conditions and you cannot tell whether the difference is you or the breakfast.

What to do: check the requirements before you buy, not after your kit arrives. If you cannot get an early morning appointment, a testosterone test will tell you less than the same test would have done earlier in the day. Full preparation detail is in Important Health Information.

5. The same test, sold four times

A common pattern in this market: several products with different names, aimed at different worries, built from one marker set with small variations. An energy test, a sleep test, a weight test, a focus test, each with a slightly different cover.

It works because worries are specific and marker sets are not. The buyer cannot tell which one they need, so they either guess or buy two, and the second one repeats most of the first.

What to do: if two products from the same seller sound different, compare the marker lists side by side. If the overlap is nearly total, you are being sold the same test twice.

A huge number of tests does the same job by a different route. Some companies list several hundred separate tests. It is presented as choice but it works as a wall. You end up comparing ten products that differ by one marker, unable to tell which one you need, and most of them were never really meant to be compared — they exist so that something matches whatever you typed into the search box. Eventually you guess, or you buy the most expensive one to be safe, or you buy nothing at all and maybe your health suffers.

What to do: treat a very large catalogue as a reason to be more careful, not less. A seller with three hundred tests should still be able to tell you which one you should get and why. If the only answer is a filter and a comparison table, you are doing their job for them.

We take the more sensible approach, and it is close to the whole reason this business exists. A small number of clearly defined tests, plus individually selectable markers on top. Nothing renamed to sound like a different product, nothing separated by a single marker to justify a second sale. You should be able to work out what you need in a couple of minutes, buy exactly that, and not spend money on a near-duplicate of something you already have.

6. Why we sell single markers only as add-ons

You can add 37 individual markers to any venous order. You cannot buy one on its own, and the reason is cost rather than policy.

A kit, the postage, and the laboratory’s per-order charge are fixed. They are the same whether the order is one marker or fifty. Added to a test you were already buying, an extra marker costs very little. Sold on its own it would have to carry every one of those fixed costs, and the price would be several times higher for exactly the same result.

So add-ons are priced to be added. That is the whole design.

7. What to ask before you buy, anywhere

Five questions. They work on any seller, including us.

• What is the total, including having my blood taken? Not the headline price.
• What exactly is on the list? Not how many markers, which ones.
• Which markers are venous-only? Some tests quietly report fewer markers on a finger-prick sample.
• Does timing matter for anything on this list? And can I meet it?
• What happens if my sample fails? Who pays for the second one, and does it include another appointment?

If a seller cannot answer all five from their own website, that tells you something.

Still not sure?

How it works covers the process end to end. Every product page carries its full marker list and preparation requirements. If you have a question about the process, email contact@n1health.co.uk and we will answer it.

And if you want to know what any individual marker actually measures, why it is tested and what moves the number, every one we run is explained in the Biomarker Guide. What the organ or system underneath it actually does is in the Body Guide.

If you want to know which test is right for your health, that is a question for your GP or a clinician who knows you, and we would rather say so than guess.