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Vitamin K

Vitamin K

Best for

Lower fracture risk in older adults

Likely strong benefit · 5–50 mg/day for 104–208 weeks · 4 meta-analyses , n=91.3k

43 papers · 6 claims · 79 outcomes scored · 5 positive

Evidence summary

Evidence summary

Likely strong benefit

Vitamin K delivers a likely strong benefit for fracture risk in older adults and for raising vitamin K levels, with the clearest evidence in bone-health trials.

  • Across 5 studies (n=91,272), vitamin K lowered fracture risk in older adults 3.
  • Across 9 studies (n=483), vitamin K raised circulating vitamin K levels in supplementation trials 1.
  • Most positive bone findings come from higher-dose, long-term vitamin K2 studies 4.

Outcomes

What vitamin k actually does, by outcome

Each row is one outcome with effect size, evidence base, the dose that worked in trials, and time to first effect. Magnitude tiers come from native-unit MCID where available, Cohen's d otherwise.

Lower fracture risk in older adults Likely strong benefit

Fewer hip, spine, forearm, and other fractures from weakened bones.

5 meta-analyses n=91k 5–50 mg 104–208 wk #1/3
18922041·19818211·28445289·36033779 +1 more
Build and maintain bone density Large effect, needs confirmation

Keeps mineral packed tightly into hip, spine, and whole-body bone.

10 meta-analyses n=7.0k 0.0094–500 mg 26–156 wk #2/8
16801507·17287908·18689371·18922041 +6 more
Raise vitamin K levels Likely strong benefit

Activates the proteins your body needs for blood clotting and bone building.

9 meta-analyses n=483 2–45000 mcg 2–104 wk
12598499·18922041·25163392·31387121 +5 more
Strengthen bones by favoring buildup Promising early signal

Your skeleton tips toward building bone faster than it breaks down.

11 meta-analyses n=7.0k 0.0094–1500 mg 1–156 wk #1/5
37338608·39657786·18922041·25654061 +7 more
Strengthen bone structure Likely modest benefit

Builds thicker walls and a denser internal framework so bones resist fracture.

2 RCTs n=313 1–45 mg 78–156 wk #1/3
17287908·37338608
Protect bones while breastfeeding Doesn't appear to help

Keeps your bone mass intact during the mineral drain of lactation.

5 meta-analyses n=5.0k 0.0094–500 mg 26–156 wk #1/4
18689371·33068157·36460034·37338608 +1 more

Forms & standardisation

The best bone data focus on K2, especially menaquinone-4, which you will often see as MK-4 or menatetrenone on the label.24 If a bottle only says 'vitamin K', check the fine print, because K1, MK-4, and MK-7 are not the same thing in the research world.12

Risk profile

Adverse events and known drug interactions

Safety events

Anaphylactic reaction severe
Hemolytic anemia severe
Hypoprothrombinemia severe
Hemorrhage severe
Pulmonary embolism severe
Deep vein thrombosis severe
nausea mild
irritability mild

Drug interactions

Warfarin major decreases effect
Orlistat moderate decreases concentration
Rifampicin moderate decreases concentration
Asciminib moderate additive
Ponatinib moderate additive
Antineoplastic Agents moderate unknown

Co-studied with

Supplements that share evidence with vitamin k

Vitamind 17 shared outcomes · d=0.48
Calcium 9 shared outcomes · d=0.98

Frequently asked

Common questions

What is the best form of vitamin K for bones?

The strongest bone and fracture data cluster around vitamin K2, especially menaquinone-4, which you will often see on labels as MK-4 or menatetrenone.24

Should I take vitamin K with food?

Yes. Vitamin K is fat-soluble, so a meal that contains fat fits the way your body absorbs it best.1

Can vitamin K interact with warfarin?

Yes. Warfarin and vitamin K work against each other, so you should not change your vitamin K intake without medical guidance.1

Does vitamin K help during breastfeeding?

The postpartum bone studies do not show a meaningful benefit for preserving spine density during breastfeeding.3

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Sources

  1. 1. Vitamin K Fact Sheet for Health Professionals
  2. 2. Vitamin K and bone health review
  3. 3. Vitamin K fracture meta-analysis
  4. 4. Menatetrenone osteoporosis trial

Generated May 15, 2026

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