My doctor ran a full panel at my 6-month keto checkup and my vitamin D came back at 22 ng/mL — clinically insufficient (below 30). My doctor says to take 2000 IU daily. I've been eating lots of fatty fish and eggs which I assumed covered vitamin D. Is vitamin D deficiency common on keto? And should I supplement, and with what?
Vitamin D deficiency is common — not keto-specific, but widespread in the population. About 40% of Americans are deficient regardless of diet. However, it's worth understanding the keto angle:
Vitamin D is fat-soluble, meaning it's absorbed with fat. This is actually an advantage of keto — dietary fat-soluble vitamins (A, D, E, K) are absorbed more efficiently when consumed with fat. Your keto diet may improve vitamin D absorption from food sources, but food sources of D are inherently limited regardless.
The main food sources (fatty fish, egg yolks, beef liver) don't contain enough to maintain optimal levels without sun exposure. Most people need to supplement or get significant sun exposure to reach optimal levels.
What to supplement with: D3 (cholecalciferol), not D2. D3 is the same form your skin makes from sun and is more effective at raising blood levels. Take it with a meal containing fat — absorption is significantly better. 2000 IU daily is conservative; many functional medicine doctors target 5000 IU to reach optimal blood levels of 40-60 ng/mL. Ask your doctor to retest at 3 months to see if 2000 IU is enough for you specifically.
K2 pairing: Vitamin D increases calcium absorption; K2 (menaquinone-7 form) directs that calcium to bones rather than arteries. The D3/K2 combination is considered best practice. Most quality D3 supplements now include K2.
22 ng/mL is below the "sufficient" threshold but symptoms of deficiency are often subtle — fatigue, mood changes, muscle weakness, increased susceptibility to illness. If you've experienced any of these and assumed it was keto adaptation, vitamin D might be part of it.
The good news: vitamin D deficiency is one of the most correctable nutritional issues. Six to eight weeks of appropriate supplementation can bring levels to optimal range and many people notice subjective improvement in energy and mood. It's also one of the cheapest supplements at roughly $10 for a year's supply.
I test vitamin D in my full panel every 6 months. Even living in Florida and being outside reasonably often, supplementing 3000 IU daily, my levels run around 52 ng/mL — optimal range. Without supplementation in previous years they were 28. Point being: even in sun-rich environments, many people need to supplement to maintain optimal levels, not just sufficient.
The Thorne D3/K2 liquid drops are what I use — 1000 IU D3 per drop with K2 included. Easy to adjust dosage, good quality source, absorbed quickly. I take 5 drops (5000 IU) daily and my levels run at 55-60 ng/mL. The liquid form taken with a fatty meal works well for me.
Retest at 3 months and share your results here. Many people need more than 2000 IU to actually reach 40+ ng/mL — the conversion from supplement to blood level varies significantly by individual based on body fat percentage (vitamin D accumulates in fat tissue), gut absorption, and baseline.