Quick answer

Take vitamin K2 with a meal that has some fat, because vitamin K is absorbed along with dietary fat; it peaks in the blood about 4 hours later. No study we found compared morning with evening doses, and MK-7 builds up with daily use, so the studies reflect a steady daily habit rather than a set hour.^1,2

Key facts

Fat eaten with spinach roughly tripled the vitamin K1 that reached the blood in a small study.³
Vitamin K is often sold combined with calcium, magnesium or vitamin D.⁴
Orlistat and bile acid sequestrants reduce how much vitamin K you absorb.⁴
People on warfarin should keep their vitamin K intake about the same every day.⁴

With a meal that has some fat

Vitamin K is absorbed the way dietary fat is, with the help of bile and digestive enzymes. Eating vegetables with some fat increases how much of their vitamin K the body takes up.¹

Supplements of K1 and of MK-7 are both absorbed well, with blood levels peaking about 4 hours after a dose.²

In a study of five volunteers, the K1 that reached the blood from spinach roughly tripled when the spinach came with butter. We found no study that tested K2 supplements with and without food, so the advice to take K2 with a meal is reasoning from how vitamin K is absorbed rather than a trial result.^1,3

Morning or night?

We found no study that compared morning and evening doses of vitamin K. The absorption studies looked at the form of vitamin K and what it was eaten with, not at the time of day.^2,3

MK-7 lingers in the blood far longer than K1 and accumulates with daily intake, so the studies of it reflect a regular daily habit rather than a particular hour. Choose the meal you are least likely to miss.²

Taking K2 with D3

K2 is often sold in one capsule with vitamin D3. Both are fat-soluble and both are taken up with dietary fat, so a single meal suits the pair. We found no study showing that taking them at different times of day changes anything.^1,5

Keeping it steady on warfarin

If you take warfarin, keeping the amount steady from day to day matters more than the time of day. NIH advises keeping vitamin K intake about the same every day, and MedlinePlus advises consistent amounts of vitamin K foods from week to week.^4,6

So do not take K2 on some days and skip it on others, and do not start or stop it without your doctor. The warfarin label calls for more frequent INR checks after any such change.^4,7

Spacing from other medicines

Orlistat and bile acid sequestrants such as cholestyramine cut how much vitamin K you absorb. Each label explains how to fit vitamins around the medicine; ask your pharmacist how that applies to your own doses.^8,9

Ask your pharmacist how far apart to take them

Orlistat, a weight-loss medicine, can reduce the absorption of vitamin K. Its label says people on warfarin who start orlistat should have their clotting tests watched closely, and advises a daily multivitamin with vitamins A, D, E and K taken at a separate time from orlistat.^1,4,8,10

On the medicine's label

Ask your pharmacist or doctor first

Bile acid sequestrants such as cholestyramine and colestipol can reduce the absorption of vitamin K and the other fat-soluble vitamins, especially over years of use. The cholestyramine label links long-term use to a bleeding tendency caused by low vitamin K, and MedlinePlus lists vitamin K supplements among the products that interact with it.^1,4,9,11

On the medicine's label

Questions people ask

Can I take vitamin K2 at night?

Yes, if that is when you eat a meal with some fat. We found no evidence that the hour matters; what the studies point to is taking it with food and taking it regularly.^1,2

Can I take vitamin K2 on an empty stomach?

It is better with food. Vitamin K is absorbed the way dietary fat is, and in a small study, fat eaten with spinach roughly tripled the vitamin K that reached the blood.^1,3

Should I take K2 and D3 at the same time?

You can. They go down well with the same meal, and no study we found shows any gain from taking them apart. If you take warfarin, ask your doctor before starting any product that contains K2.^1,4,5

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.